A gall midge recently found on Dendrobium orchids in Florida, USA, is identified as Contarinia maculipennis Felt. The identification is based on anatomical similarity to a polyphagous species originally described from Hawaii but which now appears to be from south-east Asia. Contarinia maculipennis is redescribed and compared to Contarinia solani (Rübsaamen) and C. lycopersici Felt, two species with which it has been confused in the literature.

Three highly repetitive DNA sequences Rp36, Rp217 and Rp234, have been isolated from Anopheles culicifacies Giles sensu lato. The cloned DNA sequences were found at a higher copy number in species B and C, than in species A of the A. culicifacies complex. These sequences may therefore be used as DNA probes to distinguish species A from the other two species, using a 200-fold dilution of a single mosquito DNA extract in a dot-blot hybridization assay. Rp36 and Rp217 have been completely sequenced. Internal repeats were absent in Rp36. Two related core sequences of 13 and 16 bp were found tandemly repeated in Rp217. These probes enable the rapid detection of species A of A. culicifacies in field investigations.

The possibility of density dependent feeding success in the African malaria vectors Anopheles gambiae Giles (sensu lato) and A. funestus Giles was investigated by examining the gonotrophic status of mosquitoes from 423 collections made in a Tanzanian village. Up to 500 mosquitoes were caught in any single 35 minute indoor resting collection. Estimates of the total numbers of mosquitoes resting were made by removal sampling. These indicated that the efficiency of resting collections decreased with increasing mosquito population. Of 1904 mosquito blood meals tested by ELISA, 95% were of human origin. There was no decrease in the proportion of mosquitoes fully fed at high population densities and the only demonstrable avoiding action by hosts in response to high densities of mosquitoes was the increased use of bednets during the wet season. The late biting cycle of these mosquitoes precludes many other density-dependent host defence mechanisms because the hosts are asleep at the time of attack. African malaria vectors have evolved with man and perhaps their evasion of density-dependent host responses has reinforced their preference for human blood.

Topical doses of triflumuron in acetone as low as 0.05 μg per fly induced a significant reduction in the production of viable offspring by adult Glossina morsitans morsitans Westwood, the effect being greatest in the two reproductive cycles following treatment. A dose of 0.5 μg terminated successful reproduction for the life of the fly. A single dose was as effective as the same dose split into five separate treatments. Exposure of females by tarsal contact during passage through a cotton cloth cone treated with 3% suspension concentrate of triflumuron was sufficient to terminate successful reproduction for at least four reproductive cycles following treatment. Males exposed to treated surfaces for 5 minutes could transfer effective amounts of triflumuron to females during mating for at least 2 days after treatment. Target materials, treated with 1% triflumuron in acetone and exposed to field conditions in Zimbabwe for 6 months (April to September), retained their ability to induce a peak abortion rate of 60–70% (40–45% overall) among females exposed by brief tarsal contact in the laboratory.

The life cycle of Liposcelis entomophila (Enderlein) (Psocoptera: Liposcelididae) was studied at 30 ± 1°C and 75 ± 3% r.h. The mean developmental period of the females was 22.3 days and that of the males was 18.4 days. This corresponded to the males undergoing three, and the females four, nymphal stages. A 28% developmental mortality was observed. The average number of offspring produced in the first fornight was 9.6 and the natural mortality of the females was noted only from the sixth week, increasing to 54.1% by the 12th week. An extraction and culturing regime to obtain populations of one- to three-week old adult females was developed. This procedure was also found to be ideal for L. bostrychophila Badonnel.

The vertical and horizontal distribution of Tribolium castaneum (Herbst) in a rice warehouse was studied using flight traps hung around selected stacks of bagged rice. Traps hung at 4 m or higher from the floor caught more T. castaneum than other insect species in the warehouse. At 6 m height, the traps caught mainly this species and were easy to maintain. The horizontal distribution pattern of T. castaneum sampled at 6 m was not homogeneous. The factors influencing distribution are discussed.

The continual recruitment of new individuals makes it difficult to study both the survival of multivoltine mosquitoes, and the size of the infectious reservoir in narural populations of malaria vectors. During long-term surveillance of a population of Anopheles gambiae Giles sensu lato in a Tanzanian village by daily light trapping, a temporary dry spell resulted in the cessation of recruitment for a period of 33 days, and a decline in numbers of A. arabiensis Patton caught from over 2000 to less than 10 in a sentinel house. Traps placed elsewhere in the village indicated similar proportionate declines although numbers caught varied according to location. A survival rate of 83% per day was estimated from the rate of population decline. Survival was unrelated to the size of the mosquitoes. The infectious reservoir (the chance of a mosquito acquiring an infection) was estimated to be 2% per feed. The exploitation of fortuitous events which temporarily eliminate a single stage in the life cycle has general applicability in the study of the bionomics of multivoltine insects.

In Zimbabwe, catches of Glossina morsitans morsitans Westwood and G. pallidipes Austen, at an odour source produced by up to 60 tonnes of cattle, fell by 90% from April to October 1987. With the time effect removed, the catches were: positively correlated with daily maximum temperature; up to twice as high with a trap as with an electrified target; and unaffected by the presence of an incomplete ring of electrified netting (11.5 m diameter) around the catching site. Catches increased as a power of bait mass in accord with the theory of odour dispersal. The power was ca. 0.32–0.44 for G. pallidipes, ca. 0.15 for post-teneral G. m. morsitans, 0.67 for Stomoxyinae and 0.48 for non-biting muscids. Earlier results from dose-response studies accord with the new model. Tsetse catches were 1.7–4.5 times higher with 20 tonnes of cattle as bait than with a synthetic simulate of this dose, consisting of carbon dioxide, acetone, butanone, octenol and phenolic residues. Important olfactory components thus remain to be identified. Trap efficiency for G. m. morsitans rose from 10–20% to 40% with increasing bait mass between 0 and 5 tonnes; thereafter bait mass had no effect. Increased efficiencies were also seen in Stomoxyinae (5 to 60%;) and in post-teneral G. pallidipes (45 to 70–80%). Increases in catch for bait mass greater than five tonnes were due to increased attraction rather than increased efficiency. Targets were 60–66% efficient for G. pallidipes, regardless of dose; for G. m. morsitans the efficiency was ca. 54% when unbajted and 24–35% when 60 tonnes of cattle were used as bait. The probability that G. pallidipes landed on the cloth part of the target, rather than colliding with the flanking nets, increased as the square of the bait mass for both sexes—from 0.11 to 0.22 for males and from 0.06 to 0.15 for females. There was no effect of bait mass on landing probability for G. m. morsitans and no difference between the sexes; ca. 11% of the catch landed on the cloth portion of the target. Efficiency and landing behaviour were independent of climate and season.

There is a need to identify potential biological control agents for use against noctuid pests in greenhouses. The gregarious ectoparasitoid Eulophus pennicornis (Nees) attacks a limited range of macrolepidopterous larvae, including those of some important horticultural pest species. Laboratory trials designed to investigate the biology of E. pennicornis on larvae of the tomato moth, Lacanobia oleracea Linnaeus, reveal that wasps preferentially parasitize penulitmate (fifth) or final (sixth) instar hosts. More than two-thirds of wasps lay viable eggs, and individual females oviposit on up to four hosts during their lifespan. Wasp fecundity is high, preadult development is rapid, and offspring show a markedly female-biased sex ratio. Parasitized fifth instar L.oleracea hosts do not grow as quickly as unparasitized larvae, and neither do they undergo normal ecdysis to the final larval stadium. Furthermore, the consumption of artificial diet by parasitized fifth instar hosts is greatly reduced in comparison to that of unparasitized larvae (overall feeding-reduction over a 12 day period was 64.7%). Our results suggest that E. pennicornis affects both the developmental and feeding physiology of host larvae, and that inoculative releases of this parasitoid could provide effective biological control for L. oleracea and other greenhouse pests.

The bioactivity of materials from the leaves of Ocimum kilimandscharicum was tested against Sitophilus zeamais Mots chulsky (Coleoptera: Curculionidae), Rhyzopertha dominica (Fabricius) (Coleoptera: Bostrichidae) and Sitotroga cerealella (Olivier) (Lepidoptera: Gelechiidae) in maize and sorghum grains in the laboratory. Exposure of adults of the three insect species to dried ground leaves and essential oil extract of O. kilimandscharicum induced 100% mortality after 48 h. Fresh and dried whole leaves were not toxic to Sitophilus zeamais or R. dominica. Grains treated with dried ground leaves and essential oil extract caused significant reductions in the number of progeny and survival rate of all three pest species tested. There was no adult survival or progeny production in grains treated separately with each of the two materials at doses of 25.0 g (dried ground leaves) and 0.3 g (essential oil) per 250 g of grain, respectively. Unlike R. dominica and Sitotroga cerealella, grains treated with fresh leaves enhanced the feeding activity of Sitophilus zeamais. Ground leaves and the essential oil, however, protected the grains against feeding by all three species, resulting in lower weight loss and number of damaged seeds compared with untreated grains. All the plant materials were repellent to S. zeamais with the essential oil extract applied at 0.3 g/250 g of grain evoking the highest repellent action. There was, however, considerable variation in the repellency of the materials against R. dominica and Sitotroga cerealella. The results are discussed in terms of the efficacy of O. kilimandscharicum for protection against loss due to insects in traditional grain storage in developing countries.

Pyrethroid-impregnated bednets are being used nationwide in The Gambia. The future success of this malaria control programme depends partly on the vectors remaining susceptible to those insecticides used for treating the nets. The present study was carried out on the south bank of the river Gambia, during the first large scale trial of nets in this country. Thus this area represents a sentinel site for detecting insecticide resistance in local vectors. This study gives an example of how a system of early detection for resistance problems can be set up in a relatively complex situation where multiple vectors and non-vectors are present. Samples of the Anopheles gambiae complex were caught indoors using light traps in twelve villages used in the bednet study. In all villages A. gambiae sensu stricto Giles was the predominant member of the complex as determined using the rDNA-PCR diagnostic assay. Limited bioassays with DDT and permethrin, and biochemical assays for a range of insecticide resistance mechanisms suggest that the A. gambiae complex remains completely susceptible to all major classes of commonly used insecticides including pyrethroids. Biochemical assays suggest that a low frequency of DDT resistance may occur in A. melas Theobald. This is based on elevated glutathione S-transferase levels coupled with increased levels of DDT metabolism and does not involve cross-resistance to pyrethroids. Therefore we do not envisage a decline in the efficacy of treated nets against malaria vectors in the study area in the immediate future, although monitoring should be continued whilst wide-scale use of impregnated bednets is operational.

The daytime resting sites of adult Conopomorpha cramerella (Snellen), a serious pest of cocoa in south-east Asia, were identified as a possible target to which insecticide could be selectively applied. Field observations were made on 126 resting moths in a cocoa plantation in East Malaysia. All moths were found on the undersides of branches 45° or less from horizontal, and 1·5 cm or more in diameter; 90% were found in the lower half of trees. A field trial was conducted in which 25 ppm deltamethrin was applied with knapsack sprayers to these sites. Five applications were made at ten day intervals, each crop season (6 months), over a two year period. Mean estimated losses in the sprayed area were 12.1 to 33.7 percentage points lower than in the control area, giving an estimated net benefit of up to RM978 ha in one season, assuming a cocoa price of RM4000 per tonne. Losses in the sprayed area still ranged from 7.0% to 43·1% and did not decline over successive seasons. There was some evidence for immigration into the sprayed area, but it is suggested the rapid recovery of populations following spraying is also due to the high potential rate of increase of the insect in susceptible cocoa varieties. In susceptible cocoa varieties control is always likely to be difficult, but in less susceptible varieties, and with well maintained trees, chemical control by selective application to adult resting sites can be a practical component of integrated control.

Eighteen parasitoids were recorded from the African stem borer, Busseola fusca (Fuller), on maize and grain sorghum, in Delmas and Cedara, South Africa. In Delmas, larval parasitism on both crops fluctuated below 20% with occasional peaks of 40–60%. In Cedara, larval parasitoids were active throughout the season with peaks of 75% and 60% parasitism during January and March-April, respectively on the ratoon crop, and 20% in May on the crop. Pupal parasitism peaked in Cedara at 100% during February-March, and at 80% during November, when parasitoids attacked pupae that formed after B. fusca larvae had emerged from diapause and pupated. In Delmas activity by pupal parasitoids was negligible. The egg parasitoids, Telenomus busseolae Gahan (Hymenoptera: Scelionidae) and Trichogrammatoidea lutea Girault (Hymenoptera: Trichogrammatidae), were rare. The larval parasitoid, Cotesia sesamiae (Cameron) (Hymenoptera: Braconidae), was active throughout the season and was by far the most abundant, emerging from about 90% of parasitized larvae. Its cocoons were often attacked by Aphanogmus fijiensis (Ferrière) (Hymenoptera: Ceraphronidae). Second in abundance among the larval parasitoids was Bracon sesamiae Cameron (Braconidae) whose cocoons were attacked in turn by Eurytoma braconidis Ferrière (Hymenoptera: Eurytomidae). Eurytoma braconidis was reared also from cocoons of Euvipio sp. and Aleiodes sp. (both Braconidae). All other larval parasitoids were rare. Procerochasmias nigromaculatus (Cameron) (Hymenoptera: Ichneumonidae) was the most abundant pupal parasitoid. Trichogrammatoidea lutea, Glyptapanteles maculitarsis (Cameron) (Braconidae) and Odontepyris transvaalensis (De Buysson) (Hymenoptera: Bethylidae) have not been recorded before from B. fusca. Some considerations and proposals for introductions of parasitoids into South Africa against B. fusca are discussed.

The spatial distribution of the parasitic mite Hemisarcoptes coccophagus Meyer on two armoured scale insects (Homoptera: Diaspididae) was highly aggregated in the field. Mites were more aggregated on young than on ovipositing host scale females. No differences in the mite's distribution pattern were found between latania scale (Hemiberlesia lataniae (Signoret)) and oleander scale (Aspidiotus nerii (Bouché)). Mite aggregation was density-dependent on ovipositing host females (the degree of overdispersion decreased as mite abundance increased), but density-independent on young females. The effect of density-dependent and independent mite aggregation on the proportion of hosts escaping attack at different parasite abundances was simulated, and its relevance to biological control of Diaspididae is discussed.

Adults of the dung fly Neomyia cornicina (Fabricius) (Diptera: Muscidae) were allowed to feed on cattle dung containing known quantities of ivermectin for a single period of 24 hours. The concentrations required to kill 50% and 95% of the population, within one week of feeding, were calculated to be 0.139 and 0.393 μg/g (wet weight), respectively. Ingested ivermectin was found to reduce significantly the proportion of females ovipositing and delay significantly the onset of first oviposition. For those females which did oviposit, there was no effect of ivermectin ingestion on the number of eggs laid, but the eggs of females fed dung containing ivermectin at 0.15 μg/g showed a significant reduction in percentage egg hatch.

In south India the cultivated oyster mushroom Pleurotus citrinopileatus Singer, which is treated as a subspecies of P. cornucopiae (Paul, ex Pers.) Rolland by some authors, is attacked by larvae of the phorid fly Megaselia tamilnaduensis Disney sp. n. The larvae feed on the mycelium. When more than 3% of the area of the surface of 2.5 kg cylindrical mushroom beds had been damaged the subsequent yields of sporophores fell from 400–500 g to 200–350 g. The new species is described and biological data are summarized.

A study of the age-dependent changes in the ovarioles and the age structure of a population of adult females of Anopheles gambiae in the Amani hills of north-eastern Tanzania was undertaken using the ovarian oil injection technique. The greatest difficulties encountered in accurately determining the age of members of this species are due to small size and the low parity diagnostic index of the ovary, which decreased in successive gonotrophic cycles and could drop to zero even in the first cycles. Additional information can be obtained from basal bodies, groups of six to eight cells in the calyx wall enclosed by the end of the ovariolar sheath. The possibility exists of their use for age grading of mosquitoes. The mean age of the population during the study, which was carried out in the rainy season, was rather low. The oldest were individuals that had completed four ovipositions. Among the mosquitoes infected with sporozoites were females that had completed between ≥2 and ≥4 ovipositions.

The characteristics of feeding lesions and the relationship between cocoa pod size/age and surface area were determined as a basis for examining in detail the effects of pod age on feeding and oviposition by Helopeltis theivora Waterhouse. In no-choice and choice experiments in the field, adults made few feeding lesions on the youngest cherelles and, given a choice, made many fewer on full size, ripe yellowing pods than on old cherelles and growing pods. Old cherelles and growing pods were equally attractive based on numbers of feeding lesions per cherelle or pod, but in terms of available surface area for feeding there were more on the cherelles. These distinctions in feeding choice are even more striking for oviposition, with no eggs laid on young cherelles and old pods, and old cherelles/young pods strongly preferred on a per cherelle or pod basis, and especially per unit area of surface. It is suggested that the female chooses to oviposit on relatively old cherelles and young pods because its nymphs may benefit by feeding during a nutritious growing phase of pod development. It is also significant that eggs are rarely laid on ripe pods on which newly hatched nymphs cannot survive, nor are they laid on young cherelles, most of which, unlike the oldest, will die from cherelle wilt. The female lays a large proportion of eggs within, or very close to, feeding lesions, including those made earlier by males. Yet, this does not benefit egg viability. Males did not make feeding lesions on previously laid eggs.

Mating behaviour, sex pheromone attraction and reciprocal breeding of Cotesia flavipes Cameron (Hymenoptera: Braconidae), C. sesamiae (Cameron) and C. chilonis (Matsumura) were studied. These three putative species comprise the Cotesia flavipes complex. Wing fanning and antennal vibration were the initial courtship signals from the males. Antennal stroking by the male was also an important contact signal and a prerequisite to successful mounting and copulation. Interspecific crosses revealed that males of C. flavipes exhibited courtship behaviour, and mounted and copulated with females of C. chilonis and C. sesamiae; the males transferred sperm but progeny from these crosses did not include females. Males of C. sesamiae copulated with females of C. chilonis and the progeny included viable females. The progeny backcrosses of the hybrid females to male parents also included viable females. Sex pheromone experiments were conducted in a Y-tube olfactometer and in large field cages. Males and females of C. flavipes perceived and responded to odours emitted by the opposite sex. There was no significant response to odours from conspecific individuals of the same sex in any of the three species. Pheromone bioassays in field cages using sticky traps baited with live virgin C. flavipes females attracted conspecific males.

Tsetse populations and trypanosome prevalence in cattle were monitored from 1986 to 1993 in the Ghibe valley, south-west Ethiopia. From January 1991 to December 1993 between 2000 and 4000 cattle were treated at monthly intervals with a synthetic pyrethroid insecticide, cypermethrin (RS-alpha-cyano-3-phenoxy- benzyl [1RS]-cis, trans -3-[2,2-dichlorovinyl]-2,2-dimethylcyclopropane carboxylate). An approximate dosage of 1 ml per 10 kg bodyweight was used to control tsetse flies (Glossina spp.). Treatments were given as ‘pour-on’ applications along the backlines of animals, using automatic drench-gun applicators. This resulted in a decline of 93% in the apparent density of G. pallidipes Austen. A reduction of 83% in the apparent density of G. morsitans submorsitans Newstead was also observed. This reduction was associated with a reduction in trypanosome prevalence in cattle of over 74% in 1993, despite a high level of resistance to all available trypanocidal drugs. The numbers of Stomoxys spp. (Diptera: Muscidae) and Tabanidae were also significantly reduced (P < 0.01).