The predacious mite Euseius addoensis addoensis (McMurtry) is an important predator of citrus thrips, Scirtothrips aurantii Faure, and Tetranychid mites on citrus in the eastern Cape Province of South Africa. It can also survive and reproduce on certain pollens. In this study, pollen collected from windbreaks commonly used around citrus orchards, was compared with that from Carpobrotus muirii (Mesembryanthemaceae) as a food source for predacious mites. Bioassays were conducted in the laboratory using a leaf-disk technique and both mite mortality and fecundity were recorded through one generation. Casuarina cunninghamiana (Casuarinaceae) was the only windbreak tested that produced pollen capable of sustaining E. a. addoensis for a generation with fecundity similar to that obtained with Carpobrotus muirii. Pollens collected from Pinus radiata (Pinaceae), Cupressus arizonica, C. goveniana and C. torulosa (Cupressaceae) were unsuitable. Casuarina spp. windbreaks may therefore help to maintain predacious mite populations during autumn when natural sources of prey are diminishing.

A study was carried out to investigate the behavioural components of resistance in the Standlake strain of Musca domestica Linnaeus. The flies were collected from a poultry unit where azamethiphos spray-on-bait (Alfacron), had been regularly used to control the fly population. A no-choice laboratory cage test was used to observe the responses of the Standlake resistant strain to baits and compare it with two other strains namely, Sparsholt resistant and Cooper susceptible. The baits used were, Alfacron, sugar and analytical grade azamethiphos, sugar alone, and a blank target as control. Only female flies were used, each strain was exposed separately to each bait over a 50 minute period and the responses were recorded with a datalogger. The responses (per fly) recorded during each test period were: the number of visits to a bait; the time spent on a bait; the number of feeds and time spent feeding on the bait defined as the number of proboscis contacts and the length of time of proboscis contact with the bait. Knockdown of flies was recorded at the end of each test. All strains showed differences in their responses to baits. The Standlake strain showed the greatest difference to responses to Alfacron, with inhibition of proboscis extension when flies landed on the bait and a lower proboscis contact when extended, resulting in fewer flies being knocked down by Alfacron than by the sugar and azamethiphos bait. This suggested that inhibition of feeding on the Alfacron bait by the Standlake strain was caused by formulation components or contaminants and not the active insecticide ingredient, azamethiphos.

A new species of gall midge, Procontarinia schreineri Harris, which attacks mango foliage in Guam, is described and the results of field observations on its pest status, biology and population fluctuations are reported. Eggs are laid on young mango leaves and larvae, which develop rapidly over about 5 days, induce blister galls before leaving to pupate. Secondary damage to infested foliage is caused by the fungus Colletotrichum gloeosporioides, which invades damaged leaf tissue and causes mango anthracnose disease. P. schreineri population fluctuations on mangoes were assessed at four localities on Guam over three years by counting the numbers of galls. It was concluded that the main factors affecting populations were rainfall and location. More galls were present during rainy periods, possibly because high humidity improves larval and pupal survival. Gall populations were generally low and unlikely to have direct effects on fruit yields but the introduction of new improved varieties of mango might increase susceptibility to damage. In addition, old galls on damaged leaves may provide reservoirs of anthracnose inoculum.

Megaselia chlumetiae Disney sp. n. is described from India. Its larva parasitizes larvae of Chlumetia transversa (Walker), a pest of Mangifera indica. Eggs are laid on the integument of the host larva. Newly emerged fly larva enter the host and develop by consuming the host's internal tissues. Pupariation normally takes place within the host's empty skin.

A trial was carried out using experimental huts to determine whether mosquitoes deterred from entering a building where a person slept under a permethrin-impregnated bednet would enter neighbouring dwellings where people used untreated nets. In each of the six experimental huts a man slept under a bednet for six weeks during the dry season in The Gambia. One bednet was impregnated with permethrin, the other five nets were untreated. The design of the trial was based on a series of Latin squares, so that both men and nets were rotated between huts on different nights. At the end of the trial each man had slept under each net in each hut. Mosquitoes collected from the huts each morning were used to estimate the total number of mosquitoes which had entered each hut during the night. Fewer Anopheles gambiae Giles (sensu lato), A. pharoensis Theobald and Mansonia spp. entered a hut with an impregnated bednet than those with untreated nets. However, there was no evidence that mosquitoes deterred from entering a hut with a treated net entered neighbouring huts with untreated nets. Thus it appears unlikely that people using untreated bednets in a community where most use impregnated nets would receive more bites than if everyone had an untreated net. However, the responses of mosquitoes to permethrin-impregnated bednets were found to depend both upon their species and nutritional condition since A. rufipes Gough, banded Culex spp. and non-human bloodfed A. gambiae (sensu lato) freely entered huts with a treated net.

Glossina morsitans morsitans Westwood and G. pallidipes Austen were caught hourly on electric nets from dawn to dusk in the Zambesi Valley, Zimbabwe, in cold and hot weather. When middle of the day temperatures reached only 24°C, activity of G. morsitans was at a low level from dawn to early afternoon but then rose to a dusk peak (most marked in males); G. pallidipes behaved similarly, but showed almost no activity before noon. When dawn temperatures rose above ca. 24°C (and afternoon temperatures above 38°C) the evening peak disappeared, to be replaced by a peak at dawn (and with almost no activity occurring through the rest of the day). This reversal of the more usual field activity pattern of late afternoon maxima reveals that the positive correlation between activity level and temperature at dusk (Brady & Crump, 1978) breaks down above ca. 33°C, although the earlier conclusion that the typical U-shaped activity pattern of tsetse flies is mainly driven by endogenous timing is still valid for moderate temperatures.

A seed-feeding weevil, Melanterius servulus Pascoe, is considered suitable for release against the weed Paraserianthes lophantha. However, host specificity tests have indicated that M. servulus may also develop on the seeds of Acacia mearnsii (black wattle), which is both a weed and a crop plant in South Africa. Seed orchards, which supply the black wattle industry, may therefore need to be protected. The aim of this study was to determine whether the two pyrethroid insecticides presently used in wattle plantations against the wattle bagworm (Kotochalia junodi Heylaerts (Lepidoptera: Psychidae)) are effective against M. servulus. Since M. servulus has not yet been released in South Africa, field trials were not possible, and evidence that black wattle seed orchards can be protected from M. servulus was obtained indirectly, in two stages. Firstly, field trials showed that the two insecticides effectively protect the weed Acacia longifolia from a closely related weevil, Melanterius ventralis Lea, which has already been established as a biocontrol agent. Secondly, quarantine laboratory trials demonstrated that M. ventralis and M. servulus showed similar avoidance responses and similar levels of mortality when exposed to the insecticides. All the evidence indicates that the chemical protection of A. mearnsii seed orchards from M. servulus is possible.

Six isofemale lines of the aphid parasitoid Aphelinus abdominalis (Dalman) were compared for life history traits related to parasitism of three cereal aphid species. The lines differed most in the number of hosts parasitized in 24 h and the developmental times of females and males. Cluster and discriminant analysis showed that these differences were pronounced between line I, line II and lines III-VI, but not between lines III, IV, V and VI. Cross-breeding experiments revealed reproductive barriers between the lines which proved to differ most in life history traits, indicating the possible existence of morphologically similar species. Given the variability in life history traits between lines of A. abdominalis recorded in this study, we suggest a careful selection of candidate strains for biological control will be rewarding.

The development and longevity of Amblyomma triguttatum triguttatum Koch were studied at temperatures of 15, 20, 25, 30, 35 and 40°C, and humidities with water staturation deficits of 2–3, 8–9 and 16–17 mm Hg. No stage developed at 40°C and the engorged larva was the only stage able to develop at 15°C. The rate of development was inversely related to temperature, with the exception of the pre-oviposition period of the engorged female which was longer at 35°C than at 30°C. The egg was the most vulnerable stage to high saturation deficit (low humidity) but some did survive in constant conditions of 16–17 mm Hg, showing an adaptation to harsh environments; A. t. triguttatum survives in a semi-desert habitat. The longevity of the unfed stages increased from the larvae, nymphs to adults. The longevity decreased with increase of temperature and decrease of humidity with the exception of adults maintained at 30°C and 16–17 mm Hg, which had a longer viability to the same saturation deficit at 20°C (50% mortality) and 25°C (50% and 100% mortality).

Choice between prey species by Chilocorus nigritus (Fabricius) and C. bipustulatus (Linnaeus) adults and larvae was determined. Strong preferences were absent and differences in the predators' feeding histories, were not reflected in their choices. The deleterious effects of a prey substitution, during larval development and adult maintenance, were investigated using C. nigritus with supplementary work on C. bipustulatus. These diet changes significantly retarded larval development rate, and subsequent adults were smaller than control individuals. Prey substitutions in the adult diet, suppressed oviposition for several days and feeding rate was reduced at one day after substitution. Larvae were more sensitive than adults to such diet changes. This was not a case of classical unsuitability of the new prey, as the fecundity and feeding rate returned to the same levels as before the substitution after a few days of exposure to the new prey. Furthermore, both prey types were suitable for larval development of C. nigritus when they fed on one exclusively, but unsuitable when substitutions were made. The effects of prey substitutions may possibly be attributed to the presence, in the new prey, of plant toxins, which the predators are initially not physiologically capable of dealing with in large quantities. These results present difficulties for the concepts of monophagy and polyphagy, being less well defined than normally thought. In view of coc-cinellid foraging behaviour and larval habitat selection by adults, the temporary reduction in fitness following a diet change is considered to be adaptive.

Trials for the control of soil pests, particularly of termites (Isoptera: Termiti-dae), in groundnuts (Arachis hypogaea) in India and Sudan used chlorpyrifos and isofenphos granules, chlorpyrifos, phorate, carbosulfan and carbofuran in controlled release formulations, and chlorpyrifos seed dressing. Their effects on foliar pests were also noted. Chlorpyrifos controlled release pellets were as effective as aldrin, used as a standard, in reducing root and pod attack and, like aldrin, doubled yields. Isofenphos and chlorpyrifos granules increased yields and reduced pod damage, but to a lesser extent. Other treatments were less effective. Carbosulfan and phorate controlled release and isofenphos granules reduced leaf miner attack. These trials establish the efficacy of controlling termites and other soil pests with controlled release formulations of otherwise non-persistent insecticides. However, the expensive formulation is unlikely to be cost-effective for rural farmers in developing countries and, in the case of chlorpyrifos, residue levels in kernels may be unacceptable. Future work should investigate other insecticides in the formulation and development of cheaper controlled release matrices.

The influence of the black cocoa ant Dolichoderus thoracicus (Smith) on losses due to the mirid Helopeltis theivora Waterhouse, black pod disease (caused by Phytophthora palmivora (Peronosporales)) and mammalian pests (rats, squirrels and civet cats) was studied over a two-year period in two separate fields of cocoa. Both fields initially had high D. thoracicus activity. In each field, ant-scarce plots were created by treating these plots with insecticides; ant-abundant plots existed where the plots were left untreated. An abundance of D. thoracicus clearly had a negative effect on numbers of mirids, with respectively 380 and 2222% more nymphs and adults being recorded in the ant-scarce than in the ant-abundant plots over the two-year period. An abundance of D. thoracicus did not increase black pod incidence: on the contrary it reduced incidence of the disease in both fields. The number of rat-damaged pods in ant-scarce plots was significantly higher than in ant-abundant plots in one of the fields but no significant difference was detected in the other. Regarding number of pods lost to squirrels and civet cats, no significant difference between ant-scarce and ant-abundant plots was obtained for both fields; the losses to either of these mammalian pests were extremely low. The number of healthy ripe pods in ant-abundant plots was 40.4 and 32.1% higher than in ant-scarce plots in the two fields, these increases being ascribed to protection from H. theivora damage by D. thoracicus.

Mortality of Tabanus fuscicostatus Hine females, engorged to repletion on bullocks treated with lambda-cyhalothrin impregnated ear tags, or placed on treated bullocks for periods of 15, 30, 45 or 60 s but not allowed to feed, was equal to or greater than 96%, while from 0% to 8% mortality was observed for controls. Average feeding time was significantly lower in T. fuscicostatus fed on treated bullocks (33%) than in flies fed on control bullocks, but average engorged weight was not significantly different between treatments. Mortality of T. americanus Forster females, placed on the backs of treated bullocks but not allowed to feed for periods of 15, 30, 45 or 60 s, was 16%, 44%, 76% and 100%, respectively. Results of bioassays in which flies were exposed to treated filter paper (LC50) or were topically treated (LD50) are presented per fly and per weight for T. fuscicostatus and T. lineola complex.

The cuticular hydrocarbon profiles of wild caught, male Phlebotomus argentipes Annandale & Brunetti from Kandy, Sri Lanka, and Calcutta, India, were significantly different. Using discriminant functions based on three peaks from a gas-liquid chromatogram, 89% of specimens were correctly allocated to their parent sample. These results correlate with previously reported morpho-metric differences in this species from different parts of its range. Following laboratory colonization of the Kandy strain, the cuticular hydrocarbon profiles showed a progressive change, so that wild-caught and F5 generations could be completely distinguished by discriminant function anaysis, with the F1 and F 2 as intermediates.

The stem borer, Chilo aleniellus (Strand) (Lepidoptera, Pyralidae) is recorded for the first time as a pest of maize in the western part of the forest area of Côte d'lvoire. Descriptions are given of the larva (including chaetotaxy), the pupa, and adult genitalia. The geographical distribution of this species is presented, and its importance as a pest in Côte d'Ivoire is discussed.

Adults of Autographa gamma (Linnaeus) make regular, seasonal migrations into areas where they are unable to breed continuously. Individuals migrate into Britain each spring, and after one, two or three generations, offspring of the spring migrants return to over-wintering areas in North Africa and the Middle East. The larvae are highly polyphagous and have been recorded damaging many crops, especially Brassica spp. Insects usually migrate during the adults' pre-reproductive period (PRP). The length of this period is therefore an index of migratory potential since individuals with longer PRPs have more time to express their capacity for flight and to travel further. Individuals reared outside in Britain in autumn have longer PRPs than individuals reared outside in summer. Laboratory experiments show that PRPs are extended at low temperatures and under short photoperiods and there is some evidence that PRPs are also extended under gradually decreasing photoperiods. By extending PRPs in response to environmental conditions typical of Britain in autumn, individuals are able to increase their potential for pre-reproductive migratory flight and therefore their potential for reaching suitable overwintering sites further south.

In a field of six hectares, the number of palms foraged by Anoplolepis custodiens (Smith) increased from January to December 1988 from 32 to 85% and the ant activity scores (0–3 system) from 0.5 to 2.0. During the same time, the population of the coconut bug, Pseudotheraptus wayi Brown (Heteroptera: Coreidae) as well as the damage it caused, decreased significantly. A significant relationship between low percentages of damaged nutlets and high ant scores of the palms could be established. The nut set of ant foraged palms was 2–3 times higher than that of comparable palms in an immediately adjacent field free of A. custodiens. Palms with high A. custodiens scores had invariably high scores of the coconut aphid, Cerataphis variabilis Hille Ris Lambers (Homoptera: Aphididae). The performance of the palms was not visibly affected by the aphids.

Studies on the morphology and distribution, and the role of trichomes in damage to cowpea (Vigna unguiculata) by the legume pod borer Maruca testulalis (Geyer) showed that trichome cover on individual cultivars varied in trichome length and density, but not in trichome type from different plant parts. Trichome density on different parts decreased with increasing plant age. Significant (P <0.05) negative correlations were obtained between total trichome density on pods, pod infestation and damage severity. In contrast, correlations between length of non-glandular trichomes on pods, pod infestation and damage severity were not significant. Results suggest that trichome length may be less important than density in reducing pod damage by M. testulalis in cultivated cowpeas. It is, therefore, concluded that breeding for a higher level of trichomes in high yielding and agronomically desirable cowpea cultivars, will serve as an important component in the integrated management of M. testulalis.

A seed-feeding curculionid, Rhyssomatus marginatus Fåhraeus, was introduced into South Africa for biological control of a perennial leguminous weed, Sesbania punicea, from South America. R. marginatus has become established even though its larval food source, seeds in ripening pods, is severely depleted by another biological control agent, an apionid, Trichapion lativentre (Beguin Billecocq), which destroys nearly all the flower-buds produced by the plants and reduces seed-set by 98% on average. In spite of this indirect competition, R. marginatus destroys up to 88% of the remaining seeds that develop on S. punicea, regardless of host plant location. Detrimental intraspecific interactions between larvae of R. marginatus are minimized, and the utilization of a depleted food source is optimized, through meticulous selection of oviposition sites by the female weevils. Although numerically inferior, R. marginatus is an important supplementary agent to T. lativentre and together the two species of weevils have almost arrested the reproductive potential of S. punicea.

The biology and biogeography of the economically important species of Heteropsylla Crawford, including H. cubana Crawford, are discussed. Heteropsylla comprises a group of legume-feeding neotropical psyllids within the subfamily Ciriacreminae. Taxonomic characteristics previously used to diagnose Heteropsylla and related genera are discussed and a new generic diagnosis is made using both adult and larval characters. Thirty-nine species of Heteropsylla are now recognized and each is described and illustrated. Of these, 21 are new to science. One species, H. boquetensis (Brown & Hodkinson), is transferred from Limbopsylla Brown & Hodkinson. Final instar larvae of 22 species are described and illustrated. Host-plants are recorded for 35 species, showing that Heteropsylla species are generally found on legumes belonging to the Mimosoideae. Three exceptions occur in the Caesalpinioideae. A checklist of species and keys to the identification of adult males, adult females and final instar larvae are provided.