A commercially-available, hand-applied PVC resin formulation of the sex pheromone of the striped rice stem borer, Chilo suppressalis (Walker) was used to control the yellow stem borer, Scirpophaga incertulas (Walker), in a 20 ha mating disruption trial in West Bengal, India, in 1992. Indirect measures of mating disruption were used to compare the pheromone-treated plot with an untreated control plot and a farmers' practice plot where a conventional pesticide control regime was practised. The results showed that the level of ‘white head’ damage in the pheromone-treated plot was significantly lower than that recorded in other treatment plots and that the relative percentage of the larvae of the two major stem borer species, S. incertulas and Chilo polychrysa (Meyrick) found in the region changed from 88% S. incertulas in the farmers' practice plot to 65% in the pheromone-treated plot. The yields of grain and straw recorded in the pheromone-treated plot were significantly higher than in the untreated control plot but not significantly different from those recorded in the farmers' practice plot.

Gas chromatography analysis of Lutzomyia longipalpis (Lutz & Neiva) pupae and fourth instar larvae revealed a compound which was not present in other larval stages. Squashed pupae were repellent to conspecific larvae and ants (Lasius niger (Linnaeus) (Hymenoptera: Formicidae)), whereas second and third instars were not. Hexane extracts of pupae were repellent to conspecific larvae and L. niger, but extracts of second and third instars were not. The biologically active chemical was isolated from pupae and fourth instars and was found to be repellent to conspecific larvae and L. niger. The possibility that pupae and fourth instars may use a combined chemical and mechanical defensive strategy to avoid predation and cannibalism is discussed.

The survival of Myzus persicae (Sulzer) clones, representing the full range of the recognized levels of insecticide resistance, was measured after 3–4 week exposure to the winter climate in the field. Ten separate trials were carried out using known numbers of first/second instar nymphs on unsprayed oilseed rape and groundsel. These predominantly showed a negative association between resistance level and the proportion of aphids recovered alive after exposure. The strength of the relationship correlated closely with three meteorological variables: the length of time that aphids spent below 2°C, mean rainfall and mean windspeed. We conclude that selection for resistance to insecticides is subject to counteracting selection by cold, wet and windy conditions in the UK winter. Revertant clones, that had spontaneously lost extreme resistance to insecticides despite retaining resistance genes, survived no better than aphids that had kept their high resistance, indicating that overproduction of esterase was not the reason for poor survival.

Exposure of freshly laid eggs (<24 h old) of Earias vittella Fabricius (Lepidoptera: Noctuidae) and Dysdercus koenigii (Fabricius) (Hemiptera: Pyrrhocoridae) to volatiles from bulbs of Allium sativum significantly reduced their hatchability. Eggs of Spodoptera litura (Fabricius) (Noctuidae) treated likewise, failed to hatch. Eggs of Helicoverpa armigera (Hübner) (Noctuidae) were more tolerant and showed only a slight decrease in mortality. None of the immature stages of D. koenigii and H. armigera and only 30% of those of E. vittella that hatched from treated eggs managed to complete their metamorphosis. A few larvae of H. armigera developed to the pupal stage but their pupal weights were markedly low. These findings are interpreted as the chronic effects of volatiles affecting larvae/nymphs following developmental defects sustained during embryonic development. The known chief constituents such as allicin, 2-propene sulfenic acid, 2-propene thiol, propylene, thioacrolein and ajoene present in the volatiles were presumed to be responsible for the adverse consequences reported here.

During translocations of black rhinoceros (Diceros bicornis Linnaeus) in Kenya, we studied the relationships between the rhinoceros and biting flies. In trapping experiments, rhinoceros waste products (urine or dung) were substituted for known attractants such as cow urine, l-octen-3-ol or acetone. Catches of Glossina pallidipes Austen, Glossina longipennis Corti, Stomoxys spp., and Haematopota spp. were not affected by these substitutions. NG2G and Vavoua traps sited near captive animals caught similar numbers and kinds of flies as traps set without animals. Any minor attractive properties of rhinoceros odours were probably due to the presence of known attractants such as 4-cresol and 3-n-propylphenol, which were confirmed to be present through gas chromatography—mass spectroscopy. In feeding trials with laboratory-reared tsetse, Glossina brevipalpis Newstead and Glossina morsitans centralis Machado fed well on immobilized animals, whereas G. longipennis fed reluctantly. Catches of G. brevipalpis were doubled in one trapping experiment when rhinoceros urine was used as odour bait. Philoliche spp., Haematopota spp. and other Tabanidae fed on captive rhinoceroses. Many species of Stomoxyinae were associated with rhinoceroses. Of these, the most frequent association was with Rhinomusca dutoiti Zumpt, a species found previously only in South Africa. Rhinomusca dutoiti was found in two highland rhinoceros sanctuaries, Nairobi National Park and Solio Ranch Game Reserve.

Previous studies have shown the sandfly Lutzomyia evansi to be the vector of Leishmania chagasi in northern Colombia. A longitudinal survey during seven months on the host preference of Lutzomyia evansi was conducted in the visceral leishmaniasis focus of San Andrés de Sotavento, Colombia. Host preference was determined by presenting sandflies with a choice of three baits (human, and the reservoirs dog and opossum) and a blank control in specially designed cone traps. A rotational experimental design involved 56 trap nights in which the effect of bait, proximity to forest and season could be distinguished from the potentially confounding factors of site and day to day variation. From a total of 598 sandflies caught during all experiments, females and males of Lutzomyia evansi accounted for 93.8% of the captures in the baited traps. Overall, human attracted the greatest number of sand flies, followed by the other two baits. Attraction and feeding success showed significant differences (P < 0.0001) between baits.

The encyrtid parasitoid Apoanagyrus diversicornis (Howard) (formerly known as Epidinocarsis diversicornis) failed to establish itself in Africa where it was introduced, in addition to A. lopezi De Santis for the biological control of the cassava mealybug, Phenacoccus manihoti Matile-Ferrero. Apoanagyrus lopezi is a better competitor and available evidence suggests that competition prevents the coexistence. Yet, both parasitoid species were reared from P. manihoti in the same locality in their native South America. Competition should prevent coexistence on P. manihoti in South America as well as in Africa. We investigated how A. diversicornis persists in South America. The use of alternative hosts could explain its persistence. We aimed at finding possible alternative hosts for A. diversicornis that can serve as a refuge from competition with A. lopezi. The existing information on the distribution of A. lopezi and A. diversicornis and their known hosts in South America is reviewed. Candidate alternative hosts for A. diversicornis were selected and tested. Alternative hosts should at least be suitable for development of A. diversicornis and unsuitable for development of A. lopezi. Only Phenacoccus herreni Cox & Williams met these requirements. Phenacoccus madeirensis Green, P. solani Ferris and Ferrisia virgata (Cockerell) were unsuitable hosts for both species. In cages with continuous parasitoid populations under strong interspecific competition, A. diversicornis did significantly better if half the population of P. manihoti was replaced by P. herreni. This supports the hypothesis that P. herreni can serve as an alternative host for A. diversicornis in South America and that its presence enhances coexistence of A. diversicornis and A. lopezi. Phenacoccus herreni is absent in Africa.

A vehicle-mounted net was used on 15 nights during June 1990 and 1991 in northern Oman to collect sandflies in order to identify potential vectors of visceral and cutaneous leishmaniasis. A total of 2216 sandflies was collected comprising four species of Phlebotomus and three of Sergentomyia. Catches were made every 30 minutes between 17.00 h (2 hours before sunset) and 07.00 h (1.5 hours after sunrise). Very few flies were caught before sunset. Most flies were caught at light intensities < 0.1 lux (between 20.00 and 0.500 h), but some flight activity, particularly of males and unfed females, continued even up to 07.00 h (50,000 lux, 1.25 hours after sunrise). Females of the two most abundant species, Phlebotomus alexandri Sinton and Sergentomyia clydei Sinton were significantly more active during the first half of the night (19.00-01.00 h), but males were not. Males of S. clydei showed no clear activity pattern, while males of P. alexandri had two peaks with a decline in activity around 01.00 h. Sergentomyia tiberiadis Adler & Theodor and S. fallax Parrot similarly showed different activity patterns for the two sexes. The circadian activity of females of P. alexandri and S. clydei changed during their gonotrophic cycles. Thus unfed and gravid P. alexandri had two activity peaks during the night, but the blood-fed females were most active during the first half of the night. S. clydei activity was similar, except that the gravid flies, like the blood-fed, had an early peak of activity. Too few parous females were collected to show any clear difference in activity from the nullipars.

Selected life history characteristics of Encarsia formosa Gahan parasitizing the castor whitefly, Trialeurodes ricini (Misra) were studied at three constant temperatures (20, 25 and 30°C). Egg-to-adult developmental time decreased from 32 days at 20°C to 13 days at 30°C. An average of 241 day-degrees was required to complete development above the lower threshold temperature (12°C). Juvenile mortality was 34, 40 and 47% at 20, 25 and 30°C, respectively. Mean longevity of E. formosa ranged from 7.7 days at 20°C, to 2.6 days at 30°C. Mean total fecundity ranged from 18 to 36 eggs/female. Intrinsic rate of increase (rm) increased with temperature from 0.065/day at 20°C to 0.169/day at 30°C. Generation times decreased from 37 to 14.5 days with increasing temperature.

Sympiesis hyblaeae Surekha sp. n. is described from Kerala, India. This species, which is a solitary endoparasitoid of first and second instar larvae, is a potential biological control agent of the teak defoliator Hyblaea puera (Cramer).

The development of palatable baits for the suppresion of pest termites relies on combining phagostimulants with slow-acting toxicants that termite foragers carry back to the colony and distribute to nest-mates. In the present study the palatability and toxic effects of three compounds, ampicillin, tetracycline and urea to the subterranean termites Reticulitermes flavipes (Kollar) and R. virginicus (Banks) were investigated. 1.0% solutions (w/v) of ampicillin and tetracycline applied to filter paper were unpalatable to termites in choice tests, and these concentrations depressed termite feeding, survivorship, individual biomass, and numbers of gut protozoa in no-choice tests. In contrast, urea solutions of 0.1%, 1.0% and 5.0% (w/v) were palatable to termites in choice tests, but 5.0% urea solutions depressed termite survivorship and protozoan numbers in no-choice tests. Addition of urea to tetra- cycline solutions resulted in increased palatability and decreased termite survivorship over tetracycline administered alone. The toxic effects in combination with its palatability to Reticulitermes spp. indicate that urea may be a promising candidate for termite control programmes.