Spiders (Arachnida: Araneae) from black cotton soil habitats of a highland savanna biome in Laikipia, central Kenya
- Warui, Charles M, Villet, Martin H, Young, Truman P
- Authors: Warui, Charles M , Villet, Martin H , Young, Truman P
- Date: 2004
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442705 , vital:74025 , https://tpyoung.ucdavis.edu/sites/g/files/dgvnsk4821/files/inline-files/spiders%20in%20highlands.pdf
- Description: Spiders were sampled at Mpala Research Centre, Laikipia, Kenya using pitfall trapping and sweep netting. Sampling was conducted from May 2001 to July 2002. A total of 10,487 individuals from 132 species belonging to 30 families were recorded. The family Salticidae had the highest number of species (24), followed by Gnaphosidae (20), Araneidae and Lycosidae (15 each), Theridiidae and Thomisidae (8 each) and Zodariidae (4). Most of the other families had fewer than 4 species. Throughout the study period, species not previously sampled emerged after rainfall peaks. Many species are apparently undescribed, highlighting the inadequate documentation of these taxa in Kenya. We suggest that the spider fauna of black cotton soil habitats is rich and useful for environmental monitoring, that further surveys using other collecting methods are needed, and that support for the conservation of this ecosystem should be continued. The study once more reveals the urgent need for taxonomic studies on Kenyan invertebrates.
- Full Text:
- Date Issued: 2004
- Authors: Warui, Charles M , Villet, Martin H , Young, Truman P
- Date: 2004
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442705 , vital:74025 , https://tpyoung.ucdavis.edu/sites/g/files/dgvnsk4821/files/inline-files/spiders%20in%20highlands.pdf
- Description: Spiders were sampled at Mpala Research Centre, Laikipia, Kenya using pitfall trapping and sweep netting. Sampling was conducted from May 2001 to July 2002. A total of 10,487 individuals from 132 species belonging to 30 families were recorded. The family Salticidae had the highest number of species (24), followed by Gnaphosidae (20), Araneidae and Lycosidae (15 each), Theridiidae and Thomisidae (8 each) and Zodariidae (4). Most of the other families had fewer than 4 species. Throughout the study period, species not previously sampled emerged after rainfall peaks. Many species are apparently undescribed, highlighting the inadequate documentation of these taxa in Kenya. We suggest that the spider fauna of black cotton soil habitats is rich and useful for environmental monitoring, that further surveys using other collecting methods are needed, and that support for the conservation of this ecosystem should be continued. The study once more reveals the urgent need for taxonomic studies on Kenyan invertebrates.
- Full Text:
- Date Issued: 2004
A proposed prioritization system for the management of invasive alien plants in South Africa
- Robertson, Mark P, Villet, Martin H, Fairbanks, Dean H K, Henderson, L, Higgins, Simon I, Hoffmann, John H, Le Maitre, David C, Palmer, Anthony R, Riggs, I, Shackleton, Charlie M, Zimmermann, Helmuth G
- Authors: Robertson, Mark P , Villet, Martin H , Fairbanks, Dean H K , Henderson, L , Higgins, Simon I , Hoffmann, John H , Le Maitre, David C , Palmer, Anthony R , Riggs, I , Shackleton, Charlie M , Zimmermann, Helmuth G
- Date: 2003
- Language: English
- Type: Article
- Identifier: vital:6911 , http://hdl.handle.net/10962/d1011872
- Description: Every country has weed species whose presence conflicts in some way with human management objectives and needs. Resources for research and control are limited, so priority should be given to species that are the biggest problem. The prioritization system described in this article was designed to assess objectively research and control priorities of invasive alien plants at a national scale in South Africa. The evaluation consists of seventeen criteria, grouped into five modules, that assess invasiveness, spatial characteristics, potential impact, potential for control, and conflicts of interest for each plant species under consideration. Total prioritization scores, calculated from criterion and module scores, were used to assess a species' priority. Prioritization scores were calculated by combining independent assessments provided by several experts, thus increasing the reliability of the rankings. The total confidence score, a separate index, indicates the reliability and availability of data used to make an assessment. Candidate species for evaluation were identified and assessed by several experts using the prioritization system. The final ranking was made by combining two separate indices, the total prioritization score and the total confidence score. This approach integrates the plant's perceived priority with an index of data reliability. Of the 61 species assessed, those with the highest ranks (Lantana camara, Chromolaena odorata and Opuntia ficus-indica) had high prioritization and high confidence scores, and are thus of most concern. Those species with the lowest ranks, for example, Harrisia martinii, Opuntia spinulifera and Opuntia exaltata, had low prioritization scores and high confidence scores, and thus are of least concern. Our approach to ranking weeds offers several advantages over existing systems because it is designed for multiple assessors based on the Delphi decision-making technique, the criteria contribute equally to the total score, and the system can accommodate incomplete data on a species. Although the choice of criteria may be criticized and the system has certain limitations, it appears to have delivered credible results.
- Full Text:
- Date Issued: 2003
- Authors: Robertson, Mark P , Villet, Martin H , Fairbanks, Dean H K , Henderson, L , Higgins, Simon I , Hoffmann, John H , Le Maitre, David C , Palmer, Anthony R , Riggs, I , Shackleton, Charlie M , Zimmermann, Helmuth G
- Date: 2003
- Language: English
- Type: Article
- Identifier: vital:6911 , http://hdl.handle.net/10962/d1011872
- Description: Every country has weed species whose presence conflicts in some way with human management objectives and needs. Resources for research and control are limited, so priority should be given to species that are the biggest problem. The prioritization system described in this article was designed to assess objectively research and control priorities of invasive alien plants at a national scale in South Africa. The evaluation consists of seventeen criteria, grouped into five modules, that assess invasiveness, spatial characteristics, potential impact, potential for control, and conflicts of interest for each plant species under consideration. Total prioritization scores, calculated from criterion and module scores, were used to assess a species' priority. Prioritization scores were calculated by combining independent assessments provided by several experts, thus increasing the reliability of the rankings. The total confidence score, a separate index, indicates the reliability and availability of data used to make an assessment. Candidate species for evaluation were identified and assessed by several experts using the prioritization system. The final ranking was made by combining two separate indices, the total prioritization score and the total confidence score. This approach integrates the plant's perceived priority with an index of data reliability. Of the 61 species assessed, those with the highest ranks (Lantana camara, Chromolaena odorata and Opuntia ficus-indica) had high prioritization and high confidence scores, and are thus of most concern. Those species with the lowest ranks, for example, Harrisia martinii, Opuntia spinulifera and Opuntia exaltata, had low prioritization scores and high confidence scores, and thus are of least concern. Our approach to ranking weeds offers several advantages over existing systems because it is designed for multiple assessors based on the Delphi decision-making technique, the criteria contribute equally to the total score, and the system can accommodate incomplete data on a species. Although the choice of criteria may be criticized and the system has certain limitations, it appears to have delivered credible results.
- Full Text:
- Date Issued: 2003
Analysis of the calling songs of Platypleura hirtipennis (Germar, 1834) and P. plumosa (Germar, 1834) (Hemiptera: Cicadidae)
- Sanborn, Allen F, Phillips, Polly K F, Villet, Martin H
- Authors: Sanborn, Allen F , Phillips, Polly K F , Villet, Martin H
- Date: 2003
- Language: English
- Type: text , Article
- Identifier: vital:6896 , http://hdl.handle.net/10962/d1011656
- Description: [From the introduction]: Most male cicadas produce a calling song in order to attract conspecific females. These songs have been shown to differ in closely related species (e.g. Alexander & Moore 1962; Villet 1988, 1989; Boulard 1995; Marshall & Cooley 2000; Sanborn & Phillips 2001) and in species which share habitats (e.g. Sueur 2002). The former is an inevitable part of the divergence of recognition signals that characterizes the speciation process in animals using acoustic signals (Villet 1995), while the latter would be expected from a signal that acts as a reproductive isolating mechanism (Claridge 1985; Marshall & Cooley 2000). Calling songs are therefore of value in resolving taxonomic problems in the cicadas.
- Full Text:
- Date Issued: 2003
- Authors: Sanborn, Allen F , Phillips, Polly K F , Villet, Martin H
- Date: 2003
- Language: English
- Type: text , Article
- Identifier: vital:6896 , http://hdl.handle.net/10962/d1011656
- Description: [From the introduction]: Most male cicadas produce a calling song in order to attract conspecific females. These songs have been shown to differ in closely related species (e.g. Alexander & Moore 1962; Villet 1988, 1989; Boulard 1995; Marshall & Cooley 2000; Sanborn & Phillips 2001) and in species which share habitats (e.g. Sueur 2002). The former is an inevitable part of the divergence of recognition signals that characterizes the speciation process in animals using acoustic signals (Villet 1995), while the latter would be expected from a signal that acts as a reproductive isolating mechanism (Claridge 1985; Marshall & Cooley 2000). Calling songs are therefore of value in resolving taxonomic problems in the cicadas.
- Full Text:
- Date Issued: 2003
Comparing models for predicting species' potential distributions : a case study using correlative and mechanistic predictive modelling techniques
- Robertson, Mark P, Peter, Craig I, Villet, Martin H, Ripley, Bradford S
- Authors: Robertson, Mark P , Peter, Craig I , Villet, Martin H , Ripley, Bradford S
- Date: 2003
- Language: English
- Type: Article
- Identifier: vital:6539 , http://hdl.handle.net/10962/d1005980 , http://dx.doi.org/10.1016/S0304-3800(03)00028-0
- Description: Models used to predict species’ potential distributions have been described as either correlative or mechanistic. We attempted to determine whether correlative models could perform as well as mechanistic models for predicting species potential distributions, using a case study. We compared potential distribution predictions made for a coastal dune plant (Scaevola plumieri) along the coast of South Africa, using a mechanistic model based on summer water balance (SWB), and two correlative models (a profile and a group discrimination technique). The profile technique was based on principal components analysis (PCA) and the group-discrimination technique was based on multiple logistic regression (LR). Kappa (κ) statistics were used to objectively assess model performance and model agreement. Model performance was calculated by measuring the levels of agreement (using κ) between a set of testing localities (distribution records not used for model building) and each of the model predictions. Using published interpretive guidelines for the kappa statistic, model performance was “excellent” for the SWB model (κ=0.852), perfect for the LR model (κ=1.000), and “very good” for the PCA model (κ=0.721). Model agreement was calculated by measuring the level of agreement between the mechanistic model and the two correlative models. There was “good” model agreement between the SWB and PCA models (κ=0.679) and “very good” agreement between the SWB and LR models (κ=0.786). The results suggest that correlative models can perform as well as or better than simple mechanistic models. The predictions generated from these three modelling designs are likely to generate different insights into the potential distribution and biology of the target organism and may be appropriate in different situations. The choice of model is likely to be influenced by the aims of the study, the biology of the target organism, the level of knowledge the target organism’s biology, and data quality.
- Full Text:
- Date Issued: 2003
- Authors: Robertson, Mark P , Peter, Craig I , Villet, Martin H , Ripley, Bradford S
- Date: 2003
- Language: English
- Type: Article
- Identifier: vital:6539 , http://hdl.handle.net/10962/d1005980 , http://dx.doi.org/10.1016/S0304-3800(03)00028-0
- Description: Models used to predict species’ potential distributions have been described as either correlative or mechanistic. We attempted to determine whether correlative models could perform as well as mechanistic models for predicting species potential distributions, using a case study. We compared potential distribution predictions made for a coastal dune plant (Scaevola plumieri) along the coast of South Africa, using a mechanistic model based on summer water balance (SWB), and two correlative models (a profile and a group discrimination technique). The profile technique was based on principal components analysis (PCA) and the group-discrimination technique was based on multiple logistic regression (LR). Kappa (κ) statistics were used to objectively assess model performance and model agreement. Model performance was calculated by measuring the levels of agreement (using κ) between a set of testing localities (distribution records not used for model building) and each of the model predictions. Using published interpretive guidelines for the kappa statistic, model performance was “excellent” for the SWB model (κ=0.852), perfect for the LR model (κ=1.000), and “very good” for the PCA model (κ=0.721). Model agreement was calculated by measuring the level of agreement between the mechanistic model and the two correlative models. There was “good” model agreement between the SWB and PCA models (κ=0.679) and “very good” agreement between the SWB and LR models (κ=0.786). The results suggest that correlative models can perform as well as or better than simple mechanistic models. The predictions generated from these three modelling designs are likely to generate different insights into the potential distribution and biology of the target organism and may be appropriate in different situations. The choice of model is likely to be influenced by the aims of the study, the biology of the target organism, the level of knowledge the target organism’s biology, and data quality.
- Full Text:
- Date Issued: 2003
Endothermy and chorusing behaviour in the African platypleurine cicada Pycna semiclara (Germar, 1834) (Hemiptera: Cicadidae)
- Villet, Martin H, Sanborn, Allen F, Phillips, Polly K F
- Authors: Villet, Martin H , Sanborn, Allen F , Phillips, Polly K F
- Date: 2003
- Language: English
- Type: text , Article
- Identifier: vital:6892 , http://hdl.handle.net/10962/d1011652 , http://dx.doi.org/10.1139/z03-119
- Description: Cicadas use acoustic signals to find mates and therefore offer a phylogenetically independent opportunity to test the generality of ideas about acoustic communication that were developed from studies of other animals. Pycna semiclara (Germar, 1834) (Hemiptera: Cicadidae) is a forest-dwelling platypleurine cicada that uses its calling song to form choruses and attract mates. Additionally, P. semiclara produces an encounter call that is involved in courtship and also in spacing males within choruses. Males generally call from exposed trunks and branches within the understory but clear of the undergrowth and fight with other males that call within about 50 cm of them. Choruses sing sporadically throughout the day but focus most of their calling activity into half-hour bouts at dawn and dusk. Body size and ambient temperature had no significant effect on spectral or temporal characteristics of the calling song. Body temperature measurements indicate that P. semiclara thermoregulates endothermically, with a body temperature of more than 22 °C above ambient temperature being measured during calling activity at dusk. Such endothermy provides an advantage to the cicadas by allowing them to call during crepuscular hours when atmospheric conditions are most optimal for acoustic communication and predation risks are minimal. Coincidentally, endogenously regulating body temperature allows the temporal characteristics of the call to be unaffected by ambient temperature changes.
- Full Text:
- Date Issued: 2003
- Authors: Villet, Martin H , Sanborn, Allen F , Phillips, Polly K F
- Date: 2003
- Language: English
- Type: text , Article
- Identifier: vital:6892 , http://hdl.handle.net/10962/d1011652 , http://dx.doi.org/10.1139/z03-119
- Description: Cicadas use acoustic signals to find mates and therefore offer a phylogenetically independent opportunity to test the generality of ideas about acoustic communication that were developed from studies of other animals. Pycna semiclara (Germar, 1834) (Hemiptera: Cicadidae) is a forest-dwelling platypleurine cicada that uses its calling song to form choruses and attract mates. Additionally, P. semiclara produces an encounter call that is involved in courtship and also in spacing males within choruses. Males generally call from exposed trunks and branches within the understory but clear of the undergrowth and fight with other males that call within about 50 cm of them. Choruses sing sporadically throughout the day but focus most of their calling activity into half-hour bouts at dawn and dusk. Body size and ambient temperature had no significant effect on spectral or temporal characteristics of the calling song. Body temperature measurements indicate that P. semiclara thermoregulates endothermically, with a body temperature of more than 22 °C above ambient temperature being measured during calling activity at dusk. Such endothermy provides an advantage to the cicadas by allowing them to call during crepuscular hours when atmospheric conditions are most optimal for acoustic communication and predation risks are minimal. Coincidentally, endogenously regulating body temperature allows the temporal characteristics of the call to be unaffected by ambient temperature changes.
- Full Text:
- Date Issued: 2003
Hot-blooded singers: endothermy facilitates crepuscular signaling in African platypleurine cicadas (Hemiptera: Cicadidae: Platypleura spp.)
- Sanborn, Allen F, Villet, Martin H, Phillips, Polly K F
- Authors: Sanborn, Allen F , Villet, Martin H , Phillips, Polly K F
- Date: 2003
- Language: English
- Type: text , Article
- Identifier: vital:6919 , http://hdl.handle.net/10962/d1011882
- Description: The cicada genus Platypleura has a wide distribution across Africa and southern Asia. We describe endothermic thermoregulation in four South African species that show crepuscular signaling behavior. This is the first evidence of thermoregulation in platypleurine cicadas. Field measurements of body temperature (Tb) show that these animals regulate Tb through endogenous heat production. Maximum Tb measured was 22.1°C above ambient temperature during calling activity at dusk. The mean Tb during dusk activity did not differ from the mean Tb during diurnal activity. A unique behavior for cicadas, a temperature-dependent telescoping pulsation of the abdomen, was observed in the laboratory during endogenous warm-up. This behavior is part of a unique method of heat generation in endothermic cicadas. Males generally call from trunks and branches within the canopy and appear to use endothermy even when the sun is available to elevate Tb. Endothermy may provide the cicadas with the advantage of decreasing predation and acoustic competition by permitting calling from perches that most complement their cryptic coloration patterns and that ectotherms cannot use due to thermal constraints. In addition, endothermy may permit calling activity during crepuscular hours when atmospheric conditions are optimal for acoustic communication and predation risks are minimal.
- Full Text:
- Date Issued: 2003
- Authors: Sanborn, Allen F , Villet, Martin H , Phillips, Polly K F
- Date: 2003
- Language: English
- Type: text , Article
- Identifier: vital:6919 , http://hdl.handle.net/10962/d1011882
- Description: The cicada genus Platypleura has a wide distribution across Africa and southern Asia. We describe endothermic thermoregulation in four South African species that show crepuscular signaling behavior. This is the first evidence of thermoregulation in platypleurine cicadas. Field measurements of body temperature (Tb) show that these animals regulate Tb through endogenous heat production. Maximum Tb measured was 22.1°C above ambient temperature during calling activity at dusk. The mean Tb during dusk activity did not differ from the mean Tb during diurnal activity. A unique behavior for cicadas, a temperature-dependent telescoping pulsation of the abdomen, was observed in the laboratory during endogenous warm-up. This behavior is part of a unique method of heat generation in endothermic cicadas. Males generally call from trunks and branches within the canopy and appear to use endothermy even when the sun is available to elevate Tb. Endothermy may provide the cicadas with the advantage of decreasing predation and acoustic competition by permitting calling from perches that most complement their cryptic coloration patterns and that ectotherms cannot use due to thermal constraints. In addition, endothermy may permit calling activity during crepuscular hours when atmospheric conditions are optimal for acoustic communication and predation risks are minimal.
- Full Text:
- Date Issued: 2003
Insect Pest Management and Ecological Research, G.H. Walter: book review
- Authors: Villet, Martin H
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/451735 , vital:75073 , https://hdl.handle.net/10520/EJC32546
- Description: This book is a 275-page argument for the place of theoretical biology in pest management research. Its general message is that contemporary pest management research emphasizes application of technology or strategic research at the expense of application of knowledge or tactical research, and that even the application of knowledge should actually be subservient to the development and extension of knowledge, theoretical research. Whenever we study a pest, we are presented with an opportunity to enhance, rather than merely apply, knowledge. It is argued that pest management research is currently failing itself because it is not doing this, and several areas of theoretical biology are identified as offering ways out of this situation.
- Full Text:
- Date Issued: 2003
- Authors: Villet, Martin H
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/451735 , vital:75073 , https://hdl.handle.net/10520/EJC32546
- Description: This book is a 275-page argument for the place of theoretical biology in pest management research. Its general message is that contemporary pest management research emphasizes application of technology or strategic research at the expense of application of knowledge or tactical research, and that even the application of knowledge should actually be subservient to the development and extension of knowledge, theoretical research. Whenever we study a pest, we are presented with an opportunity to enhance, rather than merely apply, knowledge. It is argued that pest management research is currently failing itself because it is not doing this, and several areas of theoretical biology are identified as offering ways out of this situation.
- Full Text:
- Date Issued: 2003
Insect Pest Management and Ecological Research, GH Walter book review
- Authors: Villet, Martin H
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442060 , vital:73952 , https://doi.org/10.1111/j.1570-7458.2009.00824.x
- Description: This book is a 275-page argument for the place of theoretical biology in pest management research. Its general message is that contemporary pest management research emphasizes application of technology or strategic research at the expense of application of knowledge or tactical research, and that even the application of knowledge should actually be subservient to the development and extension of knowledge, theoretical research. Whenever we study a pest, we are presented with an opportunity to enhance, rather than merely apply, knowledge. It is argued that pest management research is currently failing itself because it is not doing this, and several areas of theoretical biology are identified as offering ways out of this situation.
- Full Text:
- Date Issued: 2003
- Authors: Villet, Martin H
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442060 , vital:73952 , https://doi.org/10.1111/j.1570-7458.2009.00824.x
- Description: This book is a 275-page argument for the place of theoretical biology in pest management research. Its general message is that contemporary pest management research emphasizes application of technology or strategic research at the expense of application of knowledge or tactical research, and that even the application of knowledge should actually be subservient to the development and extension of knowledge, theoretical research. Whenever we study a pest, we are presented with an opportunity to enhance, rather than merely apply, knowledge. It is argued that pest management research is currently failing itself because it is not doing this, and several areas of theoretical biology are identified as offering ways out of this situation.
- Full Text:
- Date Issued: 2003
IsiXhosa insect names from the Eastern Cape, South Africa
- Mkize, Nolwazi, Villet, Martin H, Robertson, Mark P
- Authors: Mkize, Nolwazi , Villet, Martin H , Robertson, Mark P
- Date: 2003
- Language: English
- Type: Article
- Identifier: vital:6859 , http://hdl.handle.net/10962/d1011148
- Description: We present a list of isiXhosa names for a wide diversity of South African insects, and their English translations and scientific names, to contribute to bridging the knowledge gap between rural development workers and isiXhosa speakers. We interviewed 51 people in their homes at eight sites across the Eastern Cape and also included words from a published dictionary. We found 151 insect names, and categorized them into personal, dialectal and standard categories. Response-frequency distributions of the categories of names showed that the dialectal and standard lists were essentially complete. Sample accumulation curves showed levelling-off within sites and across the whole study, demonstrating that samples were adequate. The literal translations of some names show that isiXhosa speakers relate insects either to people, to their habitat and/or to their behaviour. The list can contribute to the standardization of knowledge of insects' indigenous names in South Africa for a variety of practical applications such as agricultural training and health services.
- Full Text:
- Date Issued: 2003
- Authors: Mkize, Nolwazi , Villet, Martin H , Robertson, Mark P
- Date: 2003
- Language: English
- Type: Article
- Identifier: vital:6859 , http://hdl.handle.net/10962/d1011148
- Description: We present a list of isiXhosa names for a wide diversity of South African insects, and their English translations and scientific names, to contribute to bridging the knowledge gap between rural development workers and isiXhosa speakers. We interviewed 51 people in their homes at eight sites across the Eastern Cape and also included words from a published dictionary. We found 151 insect names, and categorized them into personal, dialectal and standard categories. Response-frequency distributions of the categories of names showed that the dialectal and standard lists were essentially complete. Sample accumulation curves showed levelling-off within sites and across the whole study, demonstrating that samples were adequate. The literal translations of some names show that isiXhosa speakers relate insects either to people, to their habitat and/or to their behaviour. The list can contribute to the standardization of knowledge of insects' indigenous names in South Africa for a variety of practical applications such as agricultural training and health services.
- Full Text:
- Date Issued: 2003
Molecular identification of some forensically important blowflies of southern Africa and Australia
- Harvey, M L, Mansell, M W, Villet, Martin H, Dadour, I R
- Authors: Harvey, M L , Mansell, M W , Villet, Martin H , Dadour, I R
- Date: 2003
- Language: English
- Type: text , Article
- Identifier: vital:6953 , http://hdl.handle.net/10962/d1011986
- Description: One major aspect of research in forensic entomology is the investigation of molecular techniques for the accurate identification of insects. Studies to date have addressed the corpse fauna of many geographical regions, but generally neglected the southern African calliphorid species. In this study, forensically significant calliphorids from South Africa, Swaziland, Botswana and Zimbabwe and Australia were sequenced over an 1167 base pair region of the COI gene. Phylogenetic analysis was performed to examine the ability of the region to resolve species identities and taxonomic relationships between species. Analyses by neighbour-joining, maximum parsimony and maximum likelihood methods all showed the potential of this region to provide the necessary species-level identifications for application to post-mortem interval (PMI) estimation; however, higher level taxonomic relationships did vary according to method of analysis. Intraspecific variation was also considered in relation to determining suitable maximum levels of variation to be expected during analysis. Individuals of some species in the study represented populations from both South Africa and the east coast of Australia, yet maximum intraspecific variation over this gene region was calculated at 0.8%, with minimum interspecific variation at 3%, indicating distinct ranges of variation to be expected at intra- and interspecific levels. This region therefore appears to provide southern African forensic entomologists with a new technique for providing accurate identification for application to estimation of PMI.
- Full Text:
- Date Issued: 2003
- Authors: Harvey, M L , Mansell, M W , Villet, Martin H , Dadour, I R
- Date: 2003
- Language: English
- Type: text , Article
- Identifier: vital:6953 , http://hdl.handle.net/10962/d1011986
- Description: One major aspect of research in forensic entomology is the investigation of molecular techniques for the accurate identification of insects. Studies to date have addressed the corpse fauna of many geographical regions, but generally neglected the southern African calliphorid species. In this study, forensically significant calliphorids from South Africa, Swaziland, Botswana and Zimbabwe and Australia were sequenced over an 1167 base pair region of the COI gene. Phylogenetic analysis was performed to examine the ability of the region to resolve species identities and taxonomic relationships between species. Analyses by neighbour-joining, maximum parsimony and maximum likelihood methods all showed the potential of this region to provide the necessary species-level identifications for application to post-mortem interval (PMI) estimation; however, higher level taxonomic relationships did vary according to method of analysis. Intraspecific variation was also considered in relation to determining suitable maximum levels of variation to be expected during analysis. Individuals of some species in the study represented populations from both South Africa and the east coast of Australia, yet maximum intraspecific variation over this gene region was calculated at 0.8%, with minimum interspecific variation at 3%, indicating distinct ranges of variation to be expected at intra- and interspecific levels. This region therefore appears to provide southern African forensic entomologists with a new technique for providing accurate identification for application to estimation of PMI.
- Full Text:
- Date Issued: 2003
Phylogenetics of advanced snakes (Caenophidia) based on four mitochondrial genes
- Kelly, Christopher M R, Barker, Nigel P, Villet, Martin H
- Authors: Kelly, Christopher M R , Barker, Nigel P , Villet, Martin H
- Date: 2003
- Language: English
- Type: Article
- Identifier: vital:6960 , http://hdl.handle.net/10962/d1012005
- Description: Phylogenetic relationships among advanced snakes ( Acrochordus + Colubroidea = Caenophidia) and the position of the genus Acrochordus relative to colubroid taxa are contentious. These concerns were investigated by phylogenetic analysis of fragments from four mitochondrial genes representing 62 caenophidian genera and 5 noncaenophidian taxa. Four methods of phylogeny reconstruction were applied: matrix representation with parsimony (MRP) supertree consensus, maximum parsimony, maximum likelihood, and Bayesian analysis. Because of incomplete sampling, extensive missing data were inherent in this study. Analyses of individual genes retrieved roughly the same clades, but branching order varied greatly between gene trees, and nodal support was poor. Trees generated from combined data sets using maximum parsimony, maximum likelihood, and Bayesian analysis had medium to low nodal support but were largely congruent with each other and with MRP supertrees. Conclusions about caenophidian relationships were based on these combined analyses. The Xenoderminae, Viperidae, Pareatinae, Psammophiinae, Pseudoxyrophiinae, Homalopsinae, Natricinae, Xenodontinae, and Colubrinae (redefined) emerged as monophyletic, whereas Lamprophiinae, Atractaspididae, and Elapidae were not in one or more topologies. A clade comprising Acrochordus and Xenoderminae branched closest to the root, and when Acrochordus was assessed in relation to a colubroid subsample and all five noncaenophidians, it remained associated with the Colubroidea. Thus, Acrochordus + Xenoderminae appears to be the sister group to the Colubroidea, and Xenoderminae should be excluded from Colubroidea. Within Colubroidea, Viperidae was the most basal clade. Other relationships appearing in all final topologies were (1) a clade comprising Psammophiinae, Lamprophiinae, Atractaspididae, Pseudoxyrophiinae, and Elapidae, within which the latter four taxa formed a subclade, and (2) a clade comprising Colubrinae, Natricinae, and Xenodontinae, within which the latter two taxa formed a subclade. Pareatinae and Homalopsinae were the most unstable clades.
- Full Text:
- Date Issued: 2003
- Authors: Kelly, Christopher M R , Barker, Nigel P , Villet, Martin H
- Date: 2003
- Language: English
- Type: Article
- Identifier: vital:6960 , http://hdl.handle.net/10962/d1012005
- Description: Phylogenetic relationships among advanced snakes ( Acrochordus + Colubroidea = Caenophidia) and the position of the genus Acrochordus relative to colubroid taxa are contentious. These concerns were investigated by phylogenetic analysis of fragments from four mitochondrial genes representing 62 caenophidian genera and 5 noncaenophidian taxa. Four methods of phylogeny reconstruction were applied: matrix representation with parsimony (MRP) supertree consensus, maximum parsimony, maximum likelihood, and Bayesian analysis. Because of incomplete sampling, extensive missing data were inherent in this study. Analyses of individual genes retrieved roughly the same clades, but branching order varied greatly between gene trees, and nodal support was poor. Trees generated from combined data sets using maximum parsimony, maximum likelihood, and Bayesian analysis had medium to low nodal support but were largely congruent with each other and with MRP supertrees. Conclusions about caenophidian relationships were based on these combined analyses. The Xenoderminae, Viperidae, Pareatinae, Psammophiinae, Pseudoxyrophiinae, Homalopsinae, Natricinae, Xenodontinae, and Colubrinae (redefined) emerged as monophyletic, whereas Lamprophiinae, Atractaspididae, and Elapidae were not in one or more topologies. A clade comprising Acrochordus and Xenoderminae branched closest to the root, and when Acrochordus was assessed in relation to a colubroid subsample and all five noncaenophidians, it remained associated with the Colubroidea. Thus, Acrochordus + Xenoderminae appears to be the sister group to the Colubroidea, and Xenoderminae should be excluded from Colubroidea. Within Colubroidea, Viperidae was the most basal clade. Other relationships appearing in all final topologies were (1) a clade comprising Psammophiinae, Lamprophiinae, Atractaspididae, Pseudoxyrophiinae, and Elapidae, within which the latter four taxa formed a subclade, and (2) a clade comprising Colubrinae, Natricinae, and Xenodontinae, within which the latter two taxa formed a subclade. Pareatinae and Homalopsinae were the most unstable clades.
- Full Text:
- Date Issued: 2003
Revision of the genus Xiphoscelis Burmeister 1842 (Coleoptera Scarabaeidae Cetoniinae), with description of two new species and notes on its phylogeny and ecology
- Perissinotto, Renzo, Villet, Martin H, Stobbia, P
- Authors: Perissinotto, Renzo , Villet, Martin H , Stobbia, P
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442293 , vital:73973 , https://doi.org/10.1080/03946975.2003.10531184
- Description: Recent field work has shown that the genus Xiphoscelis Burmeister 1842 contains at least three species. The type species is re-described, and two new species are described, based on adult morphology. The distribution of all three Xiphoscelis species is mapped, and a phylogeny is proposed for the genus. Ecological data are presented and discussed in the context of the previously-reported association of members of this genus with termites.
- Full Text:
- Date Issued: 2003
- Authors: Perissinotto, Renzo , Villet, Martin H , Stobbia, P
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442293 , vital:73973 , https://doi.org/10.1080/03946975.2003.10531184
- Description: Recent field work has shown that the genus Xiphoscelis Burmeister 1842 contains at least three species. The type species is re-described, and two new species are described, based on adult morphology. The distribution of all three Xiphoscelis species is mapped, and a phylogeny is proposed for the genus. Ecological data are presented and discussed in the context of the previously-reported association of members of this genus with termites.
- Full Text:
- Date Issued: 2003
Seasonal phenology of the diamondback moth, Plutella xylostella (L.), (Lepidoptera: Plutellidae), and its parasitoids on canola, Brassica napus (L.), in Gauteng province, South Africa
- Mosiane, M S, Kfir, Rami, Villet, Martin H
- Authors: Mosiane, M S , Kfir, Rami , Villet, Martin H
- Date: 2003
- Language: English
- Type: text , Article
- Identifier: vital:6856 , http://hdl.handle.net/10962/d1011139
- Description: Canola, Brassica napus L. (Brassicaceae), is a relativelynewcrop in SouthAfrica. Several insect pests, including diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), that attack cruciferous vegetables, also attack canola. The aims of this study were to determine the seasonal phenology of P. xylostella populations on canola, and the composition, relative abundance and seasonal phenology of parasitoids attacking P. xylostella on this crop. Diamondback moth adults were monitored with synthetic sex-pheromone traps. Larval and pupal populations of P. xylostella were monitored weekly for three years at Bapsfontein and Rietondale in Gauteng province. Samples of diamondback moth larvae, pupae and parasitoid cocoons were collected and transported to the laboratory. Parasitoids that emerged were identified and their incidence recorded. Berlese funnel catches were used as an indicator of the accuracy of the visual counts. The infestation level of P. xylostella larvae was high from May to August at Rietondale, while at Bapsfontein it was high from September to December. There was a high correlation (r=0.79, P<0.001) between pheromone trap catches and subsequent larval infestations at Bapsfontein. The pheromone traps indicated that diamondback moth adults were present throughout the year. Berlese funnel catches indicated that a large number of larvae, especially first instars, were overlooked during visual plant scouting. Parasitism rates were often very high, reaching 90–100 %. The following parasitoids were recorded from field-collected P. xylostella: the larval parasitoids Cotesia plutellae (Kurdjumov) (Hymenoptera: Braconidae) and Apanteles halfordi Ullyett (Hymenoptera: Braconidae), the larval/pupal parasitoids Diadegma mollipla (Holmgren) (Hymenoptera: Ichneumonidae) and Oomyzus sokolowskii (Kurdjumov) (Hymenoptera: Eulophidae), the pupal parasitoid Diadromus collaris (Gravenhorst) (Hymenoptera: Ichneumonidae), and the hyperparasitoids Mesochorus sp. (Hymenoptera: Ichneumonidae) and Pteromalus sp. (Hymenoptera: Pteromalidae). Cotesia plutellae was the most abundant parasitoid throughout the study.
- Full Text:
- Date Issued: 2003
- Authors: Mosiane, M S , Kfir, Rami , Villet, Martin H
- Date: 2003
- Language: English
- Type: text , Article
- Identifier: vital:6856 , http://hdl.handle.net/10962/d1011139
- Description: Canola, Brassica napus L. (Brassicaceae), is a relativelynewcrop in SouthAfrica. Several insect pests, including diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), that attack cruciferous vegetables, also attack canola. The aims of this study were to determine the seasonal phenology of P. xylostella populations on canola, and the composition, relative abundance and seasonal phenology of parasitoids attacking P. xylostella on this crop. Diamondback moth adults were monitored with synthetic sex-pheromone traps. Larval and pupal populations of P. xylostella were monitored weekly for three years at Bapsfontein and Rietondale in Gauteng province. Samples of diamondback moth larvae, pupae and parasitoid cocoons were collected and transported to the laboratory. Parasitoids that emerged were identified and their incidence recorded. Berlese funnel catches were used as an indicator of the accuracy of the visual counts. The infestation level of P. xylostella larvae was high from May to August at Rietondale, while at Bapsfontein it was high from September to December. There was a high correlation (r=0.79, P<0.001) between pheromone trap catches and subsequent larval infestations at Bapsfontein. The pheromone traps indicated that diamondback moth adults were present throughout the year. Berlese funnel catches indicated that a large number of larvae, especially first instars, were overlooked during visual plant scouting. Parasitism rates were often very high, reaching 90–100 %. The following parasitoids were recorded from field-collected P. xylostella: the larval parasitoids Cotesia plutellae (Kurdjumov) (Hymenoptera: Braconidae) and Apanteles halfordi Ullyett (Hymenoptera: Braconidae), the larval/pupal parasitoids Diadegma mollipla (Holmgren) (Hymenoptera: Ichneumonidae) and Oomyzus sokolowskii (Kurdjumov) (Hymenoptera: Eulophidae), the pupal parasitoid Diadromus collaris (Gravenhorst) (Hymenoptera: Ichneumonidae), and the hyperparasitoids Mesochorus sp. (Hymenoptera: Ichneumonidae) and Pteromalus sp. (Hymenoptera: Pteromalidae). Cotesia plutellae was the most abundant parasitoid throughout the study.
- Full Text:
- Date Issued: 2003
Spray Oils Beyond 2000 Sustainable Pest and Disease Management, GAC Beatie, DM Watson, ML Stevens, DJ Rae and RN Spooner-Hart (Eds.): book review
- Authors: Villet, Martin H
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442099 , vital:73955 , https://hdl.handle.net/10520/EJC32548
- Description: Spray oils gained popularity as pesticides in the 1950s but were subsequently displaced in the market by synthetic compounds. With recent trends in legislation relating to pesticide residues, interest in these oils is reviving. This saw expression in the convening of the first international conference on spray oils in Sydney, late in 1999. The proceedings of that conference form the contents of this book, which features over 70 papers. The compilers clearly feel that one of the most important contributions is a newly proposed international classification scheme for spray oils, including explicit chemical standards and a common nomenclature, which is aimed at overcoming the existing ambiguous and dialectal system. However, the volume will have relevance to a much wider audience because it provides a broad overview of research into this neglected form of crop protection.
- Full Text:
- Date Issued: 2003
- Authors: Villet, Martin H
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442099 , vital:73955 , https://hdl.handle.net/10520/EJC32548
- Description: Spray oils gained popularity as pesticides in the 1950s but were subsequently displaced in the market by synthetic compounds. With recent trends in legislation relating to pesticide residues, interest in these oils is reviving. This saw expression in the convening of the first international conference on spray oils in Sydney, late in 1999. The proceedings of that conference form the contents of this book, which features over 70 papers. The compilers clearly feel that one of the most important contributions is a newly proposed international classification scheme for spray oils, including explicit chemical standards and a common nomenclature, which is aimed at overcoming the existing ambiguous and dialectal system. However, the volume will have relevance to a much wider audience because it provides a broad overview of research into this neglected form of crop protection.
- Full Text:
- Date Issued: 2003
Thermal responses in some Eastern Cape African Cicadas (Hemiptera: Cicadidae)
- Sanborn, Allen F, Phillips, Polly K F, Villet, Martin H
- Authors: Sanborn, Allen F , Phillips, Polly K F , Villet, Martin H
- Date: 2003
- Language: English
- Type: text , Article
- Identifier: vital:6918 , http://hdl.handle.net/10962/d1011881
- Description: Thermal responses were measured in cicadas collected in the Eastern Cape Province of South Africa. The thermal responses of 22 species from 5 biomes were determined. Shade-seeking temperature was the most variable and related to the various biomes. Mean shade-seeking temperature was greatest for species inhabiting the thicket biome and lowest for species inhabiting the forest biome. The animals that live in the thicket biome may adapt to the greater thermal stress to take advantage of a habitat that permits lower predation pressure. There is a correlation between body size and shade-seeking temperatures with smaller species exhibiting lower thermal responses within a particular habitat. This may be related to the greater heat exchange in smaller species. Heat torpor temperatures did not differ between the various biomes.
- Full Text:
- Date Issued: 2003
- Authors: Sanborn, Allen F , Phillips, Polly K F , Villet, Martin H
- Date: 2003
- Language: English
- Type: text , Article
- Identifier: vital:6918 , http://hdl.handle.net/10962/d1011881
- Description: Thermal responses were measured in cicadas collected in the Eastern Cape Province of South Africa. The thermal responses of 22 species from 5 biomes were determined. Shade-seeking temperature was the most variable and related to the various biomes. Mean shade-seeking temperature was greatest for species inhabiting the thicket biome and lowest for species inhabiting the forest biome. The animals that live in the thicket biome may adapt to the greater thermal stress to take advantage of a habitat that permits lower predation pressure. There is a correlation between body size and shade-seeking temperatures with smaller species exhibiting lower thermal responses within a particular habitat. This may be related to the greater heat exchange in smaller species. Heat torpor temperatures did not differ between the various biomes.
- Full Text:
- Date Issued: 2003
Tropical fruit pests and pollinators: biology, economic importance, natural enemies and control, J.E. Peña, J.L. Sharp and M. Wysoki (Eds.): book review
- Authors: Villet, Martin H
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/451790 , vital:75077 , https://hdl.handle.net/10520/EJC32522
- Description: This book will interest advanced students and scientists specializing in tropical fruit crops with a focus on horticulture, pollination biology, entomology and especially pest management. The introductory chapter starts with an examination of global trends and statistics in tropical fruit production, and goes on to generalize about their biology.
- Full Text:
- Date Issued: 2003
- Authors: Villet, Martin H
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/451790 , vital:75077 , https://hdl.handle.net/10520/EJC32522
- Description: This book will interest advanced students and scientists specializing in tropical fruit crops with a focus on horticulture, pollination biology, entomology and especially pest management. The introductory chapter starts with an examination of global trends and statistics in tropical fruit production, and goes on to generalize about their biology.
- Full Text:
- Date Issued: 2003
The toxicity of zinc to a selected macroinvertebrate, Adenophlebia auriculata (Ephemeroptera, Leptophlebiidae) method development
- Everitt, Victoria J, Scherman, Patricia A, Villet, Martin H
- Authors: Everitt, Victoria J , Scherman, Patricia A , Villet, Martin H
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442370 , vital:73979 , https://doi.org/10.2989/16085914.2002.9626572
- Description: The South African water quality guidelines for the protection of the aquatic environment are constantly being updated. The Centre for Aquatic Toxicology of the Institute for Water Research, Rhodes University, uses artificial streams and toxicological methods to contribute to the development and refinement of these guidelines. This study involved the use of 96-hour acute toxicity tests, using zinc sulphate as the toxicant, to determine the suitability of Adenophlebia auriculata as a potential indicator species of zinc pollution. As it is known that experimental environments (e.g. still versus flowing water systems) can influence the tolerance of a test species, the experimental system most suited to this species' abiotic requirements was determined. Static and recirculating systems were compared, with LC50 values calculated for the static systems being 91% lower than those calculated for the recirculating systems. The increased sensitivity to the toxicant under static conditions may be due to the animals being additionally stressed by the less favourable static environment. This suggests that recirculating systems are more suited for toxicity tests using this mayfly. Adenophlebia auriculata appears to be tolerant to zinc when compared to zinc LC50 values for other test species in the literature, and may therefore not be a suitable indicator of zinc pollution in an aquatic environment.
- Full Text:
- Date Issued: 2002
- Authors: Everitt, Victoria J , Scherman, Patricia A , Villet, Martin H
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442370 , vital:73979 , https://doi.org/10.2989/16085914.2002.9626572
- Description: The South African water quality guidelines for the protection of the aquatic environment are constantly being updated. The Centre for Aquatic Toxicology of the Institute for Water Research, Rhodes University, uses artificial streams and toxicological methods to contribute to the development and refinement of these guidelines. This study involved the use of 96-hour acute toxicity tests, using zinc sulphate as the toxicant, to determine the suitability of Adenophlebia auriculata as a potential indicator species of zinc pollution. As it is known that experimental environments (e.g. still versus flowing water systems) can influence the tolerance of a test species, the experimental system most suited to this species' abiotic requirements was determined. Static and recirculating systems were compared, with LC50 values calculated for the static systems being 91% lower than those calculated for the recirculating systems. The increased sensitivity to the toxicant under static conditions may be due to the animals being additionally stressed by the less favourable static environment. This suggests that recirculating systems are more suited for toxicity tests using this mayfly. Adenophlebia auriculata appears to be tolerant to zinc when compared to zinc LC50 values for other test species in the literature, and may therefore not be a suitable indicator of zinc pollution in an aquatic environment.
- Full Text:
- Date Issued: 2002
A PCA-based modelling technique for predicting environmental suitability for organisms from presence records
- Robertson, Mark P, Caithness, N, Villet, Martin H
- Authors: Robertson, Mark P , Caithness, N , Villet, Martin H
- Date: 2001
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442609 , vital:74014 , https://doi.org/10.1046/j.1472-4642.2001.00094.x
- Description: We present a correlative modelling technique that uses locality records (associated with species presence) and a set of predictor variables to produce a statistically justifiable probability response surface for a target species. The probability response surface indicates the suitability of each grid cell in a map for the target species in terms of the suite of predictor variables. The technique constructs a hyperspace for the target species using principal component axes derived from a principal components analysis performed on a training dataset. The training dataset comprises the values of the predictor variables associated with the localities where the species has been recorded as present. The origin of this hyperspace is taken to characterize the centre of the niche of the organism. All the localities (grid‐cells) in the map region are then fitted into this hyperspace using the values of the predictor variables at these localities (the prediction dataset). The Euclidean distance from any locality to the origin of the hyperspace gives a measure of the ‘centrality’ of that locality in the hyperspace. These distances are used to derive probability values for each grid cell in the map region. The modelling technique was applied to bioclimatic data to predict bioclimatic suitability for three alien invasive plant species (Lantana camara L., Ricinus communis L. and Solanum mauritianum Scop.) in South Africa, Lesotho and Swaziland. The models were tested against independent test records by calculating area under the curve (AUC) values of receiver operator characteristic (ROC) curves and kappa statistics. There was good agreement between the models and the independent test records. The pre‐processing of climatic variable data to reduce the deleterious effects of multicollinearity, and the use of stopping rules to prevent overfitting of the models are important aspects of the modelling process.
- Full Text:
- Date Issued: 2001
- Authors: Robertson, Mark P , Caithness, N , Villet, Martin H
- Date: 2001
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442609 , vital:74014 , https://doi.org/10.1046/j.1472-4642.2001.00094.x
- Description: We present a correlative modelling technique that uses locality records (associated with species presence) and a set of predictor variables to produce a statistically justifiable probability response surface for a target species. The probability response surface indicates the suitability of each grid cell in a map for the target species in terms of the suite of predictor variables. The technique constructs a hyperspace for the target species using principal component axes derived from a principal components analysis performed on a training dataset. The training dataset comprises the values of the predictor variables associated with the localities where the species has been recorded as present. The origin of this hyperspace is taken to characterize the centre of the niche of the organism. All the localities (grid‐cells) in the map region are then fitted into this hyperspace using the values of the predictor variables at these localities (the prediction dataset). The Euclidean distance from any locality to the origin of the hyperspace gives a measure of the ‘centrality’ of that locality in the hyperspace. These distances are used to derive probability values for each grid cell in the map region. The modelling technique was applied to bioclimatic data to predict bioclimatic suitability for three alien invasive plant species (Lantana camara L., Ricinus communis L. and Solanum mauritianum Scop.) in South Africa, Lesotho and Swaziland. The models were tested against independent test records by calculating area under the curve (AUC) values of receiver operator characteristic (ROC) curves and kappa statistics. There was good agreement between the models and the independent test records. The pre‐processing of climatic variable data to reduce the deleterious effects of multicollinearity, and the use of stopping rules to prevent overfitting of the models are important aspects of the modelling process.
- Full Text:
- Date Issued: 2001
Parasitism of Plutella xylostella (Lepidoptera, Plutellidae): field and laboratory observations
- Waladde, S M, Leutle, M F, Villet, Martin H
- Authors: Waladde, S M , Leutle, M F , Villet, Martin H
- Date: 2001
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442239 , vital:73969 , https://doi.org/10.1080/02571862.2001.10634397
- Description: Investigations carried out at Alice and its rural environs in the Eastern Cape province of South Africa, showed that parasitoids affecting the diamondback moth Plutella xylostella (L.) (Lepidoptera: Plutellidae) were Cotesia plutellae, Apanteles eriophyes, Diadegma sp., Diadromus collaris, Oomyzus sokolowskii and Hokeria sp. Cotesia plutellae was active all year round and accounted for 30–50% parasitism of P. xylostella. Field experiments using three cabbage cultivars, grown under pesticide-free conditions, indicated that C.plutellae achieved rates of parasitism as high as 90–95% for at least eight months of the year. In winter and early spring parasitism by C. plutellae was less than 30% in the field. This level of parasitism coincided with rising pest density resulting in a pest increase in early spring when C. plutellae appeared unable to control the high pest numbers. Towards the latter part of spring and early summer, C. plutellae parasitism and that of the other parasitoids increased. The possibility of using indigenous parasitoids especially C. plutellae in the management of P. xylostella in this area requires further investigation.
- Full Text:
- Date Issued: 2001
- Authors: Waladde, S M , Leutle, M F , Villet, Martin H
- Date: 2001
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442239 , vital:73969 , https://doi.org/10.1080/02571862.2001.10634397
- Description: Investigations carried out at Alice and its rural environs in the Eastern Cape province of South Africa, showed that parasitoids affecting the diamondback moth Plutella xylostella (L.) (Lepidoptera: Plutellidae) were Cotesia plutellae, Apanteles eriophyes, Diadegma sp., Diadromus collaris, Oomyzus sokolowskii and Hokeria sp. Cotesia plutellae was active all year round and accounted for 30–50% parasitism of P. xylostella. Field experiments using three cabbage cultivars, grown under pesticide-free conditions, indicated that C.plutellae achieved rates of parasitism as high as 90–95% for at least eight months of the year. In winter and early spring parasitism by C. plutellae was less than 30% in the field. This level of parasitism coincided with rising pest density resulting in a pest increase in early spring when C. plutellae appeared unable to control the high pest numbers. Towards the latter part of spring and early summer, C. plutellae parasitism and that of the other parasitoids increased. The possibility of using indigenous parasitoids especially C. plutellae in the management of P. xylostella in this area requires further investigation.
- Full Text:
- Date Issued: 2001
Preliminary observations on the effects of hydrocortisone and sodium methohexital on development of Sarcophaga (Curranea) tibialis Macquart (Diptera: Sarcophagidae), and implications for estimating post mortem interval
- Musvasva, E, Williams, Kirstin A, Muller, Nikite W J, Villet, Martin H
- Authors: Musvasva, E , Williams, Kirstin A , Muller, Nikite W J , Villet, Martin H
- Date: 2001
- Language: English
- Type: text , Article
- Identifier: vital:7075 , http://hdl.handle.net/10962/d1009532
- Description: Larvae of Sarcophaga (Curranea) tibialis (S. tibialis) were reared at constant temperature on chicken liver treated with a steroid or a barbiturate at concentrations that would be lethal, half-lethal and twice-lethal doses for humans. Trends to greater mortality at higher drug concentrations were not statistically significant. Larvae exposed to either drug took significantly longer to reach pupation compared to those in the control, while larvae exposed to sodium methohexital passed through pupation significantly faster than those in the control. No systematic relationship was found between drug concentration and development time of larvae or pupae. The total developmental period from hatching to eclosion did not differ between treatments, implying that estimates of post mortem intervals- (PMI) based on the emergence of adult flies will not be affected by the involvement of these drugs in a case. On the other hand, anomalous pupation spans may indicate the presence of barbiturates. These findings are compared with patterns found in another fly fed other contaminants.
- Full Text:
- Date Issued: 2001
- Authors: Musvasva, E , Williams, Kirstin A , Muller, Nikite W J , Villet, Martin H
- Date: 2001
- Language: English
- Type: text , Article
- Identifier: vital:7075 , http://hdl.handle.net/10962/d1009532
- Description: Larvae of Sarcophaga (Curranea) tibialis (S. tibialis) were reared at constant temperature on chicken liver treated with a steroid or a barbiturate at concentrations that would be lethal, half-lethal and twice-lethal doses for humans. Trends to greater mortality at higher drug concentrations were not statistically significant. Larvae exposed to either drug took significantly longer to reach pupation compared to those in the control, while larvae exposed to sodium methohexital passed through pupation significantly faster than those in the control. No systematic relationship was found between drug concentration and development time of larvae or pupae. The total developmental period from hatching to eclosion did not differ between treatments, implying that estimates of post mortem intervals- (PMI) based on the emergence of adult flies will not be affected by the involvement of these drugs in a case. On the other hand, anomalous pupation spans may indicate the presence of barbiturates. These findings are compared with patterns found in another fly fed other contaminants.
- Full Text:
- Date Issued: 2001