The adult Auchenorrhyncha community within the understorey of a montane tropical forest in Vietnam is described A total of 1132 specimens representing 223 morphospecies and 16 families was found in a 4300-sweep sample None of the species exceeded the 5% dominance level More than half the species are represented by single individuals within the 309 ms of vegetation Spatial community pattern is mosaic like at a scale of hundreds of metres as the similarity of 100 sweep samples does not depend on their spatial distance Areas 1 5–3 km distant from one another differ markedly in their Auchenorrhyncha communities These between-site differences exceed the intra-site community heterogeneity Population density of Auchenorrhyncha species is not correlated with their body size The Auchenorrhyncha community within a forest markedly differs from the community of an adjacent ruderal area A transitional zone between these habitats is intermediate in Auchenorrhyncha species composition

In the Cerrado of Itirapina, Brazil, 34% of the shrubs of Didymopanax vinosum (Araliaceae) were colonized by the honeydew-producing homopteran Aconophora teligera (Membracidae) which was found exclusively on this species of plant. Correlations were made between membracid density and ant frequency, as well as between these parameters and plant damage. We found that: (1) ant frequency was higher on branches with membracids and both were more frequently found near apical meristems; (2) herbivore damage was lower on apical meristems where the membracids concentrate than on ones where they are absent; (3) the presence of membracids on the plant was correlated with a reduction in the occurrence of other potential herbivores, especially on the branches housing membracids; (4) plants with more tillers tended to have a larger number of membracids. The data suggest that the presence of A. teligera and associated ants probably reduce herbivory on apical meristems of D. vinosum.

PCR-based techniques to investigate predator-prey trophic interactions are starting to be used more widely, but factors affecting DNA decay in predator guts are still poorly understood. Here, we investigated the effects of time since feeding, temperature and amplicon size on the detectability of prey DNA in the gut content of two closely related predator species. Cereal aphids, Sitobion avenae, were fed to the carabid beetles Pterostichus melanarius and Nebria brevicollis. Beetles were allowed to digest their meal at 12°C, 16°C and 20°C, and batches of beetles were subsequently frozen at time periods from 0–72 h after feeding. Aphid DNA was detected within beetles' gut contents using primers amplifying fragments of 85, 231, 317 and 383 bp. Prey DNA detection rates were significantly higher in N. brevicollis than in P. melanarius, indicating fundamental dissimilarities in prey digestion capacities. High temperatures (20°C) and large amplicons (383 bp) significantly decreased detection rates. The shortest amplicon gave the highest prey DNA detection success, whereas no differences were observed between the 231 bp and the 317 bp fragment. Our results indicate that factors such as ambient temperature, predator taxon and amplicon size should all be considered when interpreting data derived from PCR-based prey detection. Correction for such factors should make calculation of predation rates in the field more accurate and could help us to estimate when predation events occur in the field.

To determine whether host body size is the currency used by the aphidiine parasitoid, Lysiphlebus ambiguus Haliday (Hymenoptera: Braconidae), in assessing host quality, the aphid, Aphis fabae Scopoli (Homoptera: Aphididae), was reared at either high or low temperature to yield hosts of the same instar with different body sizes. Cohorts of A. fabae raised at 15°C and 30°C and exposed to individual female L. ambiguus in no-choice tests were successfully parasitized in all host stages from 1st instar nymphs to adults. However, younger and smaller aphids were more susceptible to parasitism than older and larger nymphs or adults, as measured by the number of mummies produced. For aphid cohorts reared at 15°C, the proportion of female progeny, progeny adult size, and development time all increased linearly with aphid size at the time of attack. In contrast, for aphid cohorts raised at 30°C, the proportion of female progeny and progeny adult size declined with aphid size, while development time remained unaffected. Through manipulation of host rearing temperature, we have shown that at cooler temperatures the koinobiont parasitoid, L. ambiguus, responds to host size in the same way as an idiobiont parasitoid, but that this response is compromised at higher temperatures. Our results suggest that differential mortality during development is likely to influence the observed secondary sex ratio in relation to aphid size for aphid cohorts raised at higher temperatures due to disruption of the activity of the host's primary endosymbiont and that such reduced nutritional quality of aphids cannot be compensated by increased development time.

Field studies were conducted to characterise the effects of infestations by adult and nymphal stages of cowpea aphid, Aphis craccivora Koch, on the growth and yield of cowpea, Vigna unguiculata (L.) Walp. Seedling, flowering, and podding stage plants of aphid-resistant (cv. ICV-12) and aphid-susceptible (cv. ICV-1) cowpea cultivars were used in the studies. Four treatments (consisting of infestations with adult and nymphal aphids, caged controls and uncaged controls) were administered on plants for 22 days post-treatment. Eight parameters of crop success were measured: extended leaf heights (ELH); plant mortality; incidence of sooty mould; incidence and abundance of natural enemy species; crop growth parameters (net assimilation rate, [NAR] in g/ dm2/day, and crop growth rate [CGR] in g/dm2 land surface/day); and plant yields (seeds per pod, weight per seed). Data were analysed using analysis of variance (ANOVA), orthogonal contrasts and 95% confidence intervals (C.I.). There were no significant (P > 0.05) differences between adult and nymphal infestations or between caged and uncaged controls, so the respective sets of data were combined for comparisons of aphid infestations with control treatments. Infestations caused severe plant stunting and other growth deformities, drastic yield reductions, higher plant mortality, greater incidence of natural enemies and abundance of Cheilomenes spp. on cv. ICV-1 than on cv. ICV-12, and on infested and uninfested plants. Aphid infestations did not significantly affect the incidence of sooty mould on plants of cv. ICV-12 or cv. ICV-1.

Polyacrylamide gel electrophoresis was carried out on Nephotettix virescens (Distant) adults collected from India, Sri Lanka and the Philippines, and maintained in glass-houses on rice variety TN-1 at the University of Wales, Cardiff, United Kingdom. The following enzymes showed activity and were recorded: acid phosphatase (ACP), a-glycerophosphate dehydrogenase (aGPD), fumarase (FUM), glucose-6-phosphate dehydrogenase (G-6-PDH), glutamate dehydrogenase (GLUD), glutamate oxalo-acetate transaminase (GOT), hexokinase (HK), lactate dehydrogenase (LDH), malic enzyme (ME) and xanthine dehydrogenase (XDH).

The bands in nine enzymes were homologous across the three populations and showed no differences.The relative mobility of the enzyme GLUD in the Philippines population was lower than in the other two populations and could be used for diagnostic separation.

The results confirm previous reports of differences in the relative mobility of esterase bands of the Philippines population of N. virescens from India and Sri Lanka populations on starch gel.

Experiments carried out in a coffee plantation to determine the developmental period of Icerya paltersoni (Newst.) showed that the female and male scales lasted 157 and 129 days on average, respectively. The different stages of I. pattersoni females were found to be recognizable by the number of antennal segments. The antenna of the stage I nymphal instar is six segmented, stage II is nine segmented and stage III is eleven segmented. The antenna of adult males is eighteen segmented. Females are neotenic but the males possess a pair of grey wings and atrophied mouthparts. In the field the I. pattersoni pest population size is highest in the heavy rainfall months of April and May.

When the compound eye of the adult of the planthopper, Myndus crudus, is light-adapted, pigments are condensed in a zone proximal to the crystalline cones. Viewed externally, the eye is straw-colored. When dark-adapted, pigments migrate distally into the region of the crystalline cones and thus are closer to the cuticle. Viewed externally, the dark-adapted eye is maroon-colored. The eyes of most adult M. crudus observed during daylight hours were light-adapted. Eyes of males and females changed from the light to the dark-adapted condition between sunset and ½hr after sunset. When planthoppers with light-adapted eyes were placed abruptly into darkness at a temperature of 25–27°C, the eyes became dark-adapted within 15–30 min. When planthoppers with dark-adapted eyes were placed abruptly into light, the eyes became light-adapted within 30–60 min. At 8°C the planthoppers were immobile, and light-adapted eyes had not changed to the dark-adapted condition within 45 min. Eyes of M. crudus nymphs, which live in the root zones of grasses, are dark red and do not change color in response to changes in light. Field samples showed that adult M. crudus were active in coconut palms during the day and night, but higher numbers were caught during the day (P < 0.01).