Soil type selection for oviposition by gravid females of the armoured ground cricket Acanthoplus speiseri Brancsik (Orthoptera: Tettigoniidae), a pest of grain crops in Zambia, was investigated. Twenty randomly collected samples of different types of soil, each replicated five times in an oviposition choice tray, were made available to 20 gravid females maintained in an environmental chamber, and the number of egg pods deposited per soil sample recorded. Physical and chemical characteristics of each soil sample were analysed. Properties of the soil that served as important cues to soil type selection for oviposition by the gravid females were identified and used to develop a best subset regression analysis model, for use by farmers to predict egg pod numbers of the pest in soils collected from their crop fields. There were significant differences (P<0.05) in the mean number of egg pods deposited per soil sample. Acidic, loam, clay loam and sandy loam soils with a pH range of 4.41–6.62, were the preferred soil types for oviposition. The single most important soil quality that accounted for much of the variation observed in mean egg pod number among the soil samples was pH (adjusted r2=0.1152). This was followed by mineral composition, particularly of the elements K (adjusted r2=0.1084) and P (adjusted r2=0.0731). Characteristics of the 20 soil samples tested are presented. Impacts of interactions among the soil characteristics on mean egg pod number are explained and the procedure for using the developed predictive model by farmers in crop protection is discussed.

A study was conducted at Mtwapa in the northern coastal area of Kenya during the long and short rainy seasons of 1999 and 2000 to assess the benefits of agroecosystem diversification—through agroforestry and intercropping—on the activity of natural enemies of maize stemborers. Treatments consisted of maize and cowpea intercrops or maize monocrops planted within hedgerows of Leucaena leucocephala and Gliricidia sepium. The plots were mulched or unmulched and insecticide-treated or not. The maize stemborers encountered, in order of abundance, were Chilo partellus, Chilo orichalcociliellus and Sesamia calamistis. The egg parasitoids Trichogramma spp. and Telenomus spp. were recovered from stemborer eggs. Ants, ladybird beetles, earwigs and crab spiders were found predating on the eggs. The larval parasitoids recovered included Cotesia sesamiae, Cotesia flavipes and Goniozus indicus, and the pupal parasitoid was Pediobius furvus. Mean rates of stemborer egg parasitism were generally high (>70%) while larval and pupal parasitism rates were low (<10%) for all the treatments. The observed rates of parasitism did not support the natural enemies hypothesis, which predicts that natural enemy activity increases with increasing agroecosystem diversity. Predation, larval and pupal mortality rates were generally low in all the treatments (<10%), with no significant differences between treatments.

The ovipositional response, larval orientation, larval settling, feeding, food assimilation, growth and development of maize stemborer Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae) on a susceptible maize (Zea mays L.) genotype (Inbred A) was compared to five wild plant species of the family Poaceae (Gramineae) in the laboratory and greenhouse. The intensity of oviposition differed among the test plants. Pennisetum purpureum Schumach was the most preferred test plant for oviposition when offered in a two-choice situation with maize. Likewise, P. purpureum and Sorghum versicolor Anderss were the most preferred test plant for oviposition when offered in multiple-choice tests. In no-choice tests C. partellus responses to the test plants were not significantly different. The number of first instar larvae that settled on leaf cuts of test plants in Petri dishes was significantly higher on maize and S. versicolor than on the other test plants at 24 h after infestation in a multiple-choice test. No significant differences were observed in larval settling among wild grasses at 4 h and 24 h after infestation in a no-choice test. In a two-choice test there was no significant difference in the number of neonate larvae that settled on maize and S. versicolor at 1 h and 24 h after infestation. Feeding by fourth-instar larvae was significantly higher on maize than on Echinochloa pyramidalis (Lam.) and Hyparrhenia rufa (Nees) Stapf. Larvae fed on maize assimilated significantly more food than those fed on E. pyramidalis, Panicum maximum Jacq. or H. rufa. Larval growth and development was significantly faster on maize and S. versicolor in comparison to other test plants.

Two shaving methods, one by using a sharp razor blade and the other a small pair of dissecting scissors, were tested on pods of Vigna vexillata accessions to investigate the effect of trichomes on feeding and development of the pod-bug Clavigralla tomentosicollis Stål (Hemiptera: Coreidae). Electron micrographs of unshaved (control) pods showed that all trichome types (glandular, long non-glandular and short non-glandular) were present on the pod surface. Shaving with a pair of scissors shortened long non-glandular trichomes, with little or no damage to the glandular types. Percentages of seed damage and nymphs surviving to the adult stage were similar (P>0.05) between unshaved and scissors-shaved pods. These pods showed significantly lower (P<0.05) percent seed damage than razor-shaved and solvent-washed pods, whose glandular trichomes were all completely scraped or washed off. The opposite trend was observed for the insect's growth index, indicating that glandular trichomes had a greater influence than non-glandular trichomes on feeding and development of C. tomentosicollis. The present study suggests that the scissor-shaving method would be more appropriate if the effect of trichome length is being investigated, and the more abrasive razor-shaving method if the effect of glandular trichomes is of interest

The reproductive activity and the offspring development of the bruchid Callosobruchus maculatus (Coleoptera: Bruchidae) were monitored in the seeds of seven cultivars of Cicer arietinum and three cultivars of Vigna unguiculata. The number of eggs laid by the C. maculatus was higher on the V. unguiculata cultivars than on those of C. arietinum. The survival rate during the embryonic development was higher than 90% regardless of the plant species and cultivars while the post-embryonic development rates did not differ significantly between the cultivars. However, the duration of the embryonic and post-embryonic development and the weight of the emerging females varied with seed species. V. unguiculata seeds allow a higher reproduction and a better development than C. arietinum. In this study, no cultivar had been found to be resistant. In Algeria, C. maculatus can develop in stored grains of both chickpea and cowpea, and it is a major stored grain insect pest.

Root bark extracts of five Meliaceae species (Turraea abyssinica Hochst., Turraea wakefeldii Oliv., Turraea mombassana Hiern ex C.DC., Trichilia roka (Forsk) Chiov. and Melia volkensii Guerke.) and different fractions thereof (following chloroform extraction and column chromatographic separation) were compared for their immediate toxicity and long-term effects on Anopheles gambiae Giles sensu stricto (Diptera: Culicidae). Larvicidal effects of the extracts appeared to be largely associated with limonoids of medium polarity with M. volkensii and T. mombassana extracts being more potent than those of the other Meliaceae. Long-term (6–8 days post-exposure) observations at lower doses showed that 100% cumulative mortality can be achieved with some extracts (particularly those of T. mombassana and M. volkensii) with interesting growth-inhibition effects. Follow-up studies that are needed and practical implications of the results in terms of development of larval control strategies for African malaria vectors are discussed.

To investigate the existence of inter-strain fecundity in the groundnut beetle Careydon serratus, the fecundity and larval survival of crosses of beetle strains from Bauhinia, Cassia, Piliostigma and Tamarindus were studied. The crosses produced viable eggs, but the fertility of beetles mated within strains was significantly higher than that of inter-strain matings, the former being nearly double the latter. Differences in larval mortality between the various crosses were also observed.

Bionomics, morphometric measurements and partial mitochondrial cytochrome oxidase I gene (mtCOI) sequences were examined for a population of Bemisia afer (Priesner & Hosny) (Hemiptera: Aleyrodidae) collected from cassava in Uganda. The development of the eggs, first to fourth instar nymphs and adults required respectively, 12, 31 and 10 days, with a total life duration of approximately 53 days on the cassava cultivar Ebwanateraka. Each female laid one egg per day for 13 days and about 40% of the eggs failed to develop into adults. The male: female sex ratio was 1:4. The length and width of the four nymphal instars were positively correlated (correlation coefficient=0.97). Females were bigger than males and the sexes differed significantly based on body length (P<0.001) and width (P<0.001). Overlaps in their body sizes, however, makes sex assignment based on size alone unreliable. The B. afer population shared 68% mtCOI sequence (817 nucleotides) identity with a cassava Bemisia tabaci population (Namulonge) from Uganda. This is the first study on B. afer fecundity and morphometrics, and the variability that might exist in this species is discussed.

On the island of Madagascar and five neighbouring islands: Aldabra, the Comoros, Mauritius, Réunion and the Seychelles, the number of hitherto found Ptyctima species is 57, including 37 Phthiracaroidea (of which ten are new to science), 18 Euphthiracaroidea (one new to science) and two Mesoplophoroidea. Of those 57 species, 30 are endemic (53%), ten Ethiopian species (17%), 12 pantropical species (21%) three oriental (5%) and two semicosmopolitan (3%). Endemism of Phthiracaroidea (62%) is similar to Euphthiracaroidea (59%). Similarity between the ptyctimous fauna of Madagascar and the neighbouring islands is very small—only one or two species are common. Moreover, the fauna of Mauritius is completely different from that of Madagascar. The ptyctimous fauna of Madagascar and the near islands must have been shaped before separation of Madagascar from Africa, which is suggested by the presence of the phylogenetically oldest and the youngest genera of Phthiracaroidea and Euphthiracaroidea. On the other hand, a large number of species of late derived genera Notophthiracarus and Hoplophorella may indicate a relatively late colonization of the islands by Phthiracaroidea. Dispersion of Ptyctima onto Madagascar and the neighbouring islands took place from the east—the Oriental region or from the south—the Australian region.

In studies aimed at optimizing the substrate for rearing Helicoverpa armigera (Hübner) under laboratory conditions, the noctuid's oviposition behaviour was studied in the laboratory using pigeonpea leaves, muslin cloth, tissue paper and cotton wool as oviposition substrates in free-choice and no-choice tests. Egg counts revealed the moth's preference for oviposition substrate, in descending order, to be cotton wool, pigeonpea leaves, tissue paper and muslin cloth. The preference index of cotton wool was 65% higher than the least preferred substrate, muslin cloth. A total of 300 eggs per female were laid in the free-choice tests, while 200 were laid in the no-choice assays.

An acetone extract of Solanum trilobatum leaves was evaluated for its ovicidal activity on the mosquito species Culex quinquefasciatus and Culex tritaeniorhynchus, by exposing eggs ranging in age from 0 to 18 h to concentrations of 50–200 ppm of the extract, and assessing their percent hatchability. A 100-ppm dose of the extract killed all of the eggs from both species aged between 0 and 6 h. The 50- and 75-ppm concentrations were also highly effective against young eggs; the effect declined in older eggs. The extract was more ovicidal towards C. quinquefasciatus than C. tritaeniorhynchus. On a testé l'activité ovicide d'un extrait à l'acétone de feuilles de Solanum trilobatum sur les deux espèces de moustiques, Culex quinquefasciatus et Culex tritaeniorhynchus, en exposant des œufs âgés de 0 à 18h à des concentrations de l'extrait compris entre 50 et 200ppm et en évaluant le pourcentage d'éclosions. La concentration à 100ppm de l'extrait tue tous les œufs d'âge compris entre 0 et 6h des deux espèces de moustique. Les concentrations à 50 et 75ppm sont également très efficaces contre les jeunes œufs, mais l'effet diminue avec l'âge des œufs. L'extrait est plus efficace vis à vis de C. quinquefasciatus que de C. tritaeniorhynchus.