Survival, size and development time were measured for larvae of Lucilia cuprina (Wiedemann) reared in artificially induced strikes on sheep. Between 477 and 18 000 eggs or larvae were implanted in the fleece of 42 sheep. Survival was found not to depend significantly on implant numbers. Size and development time were significantly but only weakly dependent on implant numbers. These results contrast markedly with L. cuprina's performance on carrion.

Significant differences in nymphal development period and fecundity were observed between five populations of Cicadulina mbila (Naudé) and C. triangula Ruppel from three climatic zones in Nigeria: rain forest (Ibadan), southern part of Sudan savanna (Kadawa, Kano) and the Jos Plateau. The C. triangula population that is used in mass rearing for resistance screening at the International Institute of Tropical Agriculture (IITA), Ibadan, developed much more rapidly than the wild C. triangula population from Ibadan. Similarly, the C. mbila population from the Kadawa Irrigation Scheme, Kano, developed more rapidly than the population from the Jos Plateau. All Cicadulina populations were 3–4 times as prolific on pearl millet as on maize, sorghum or the grass Digitaria exilis. The IITA colony of C. triangula was significantly more fecund than C. mbila. It is clear that Cicadulina species and populations with high reproductive potential would be most suitable for mass rearing for resistance screening to the maize streak virus disease.

In a variety of laboratory and field experiments, avermectins have been tested against some 84 species of insects in ten orders, most of which are pests of livestock or horticultural crops or are of general nuisance value. This work is reviewed, comparing doses used, methods of application, and responses of the insects. Avermectins (abamectin and ivermectin) are toxic to almost all insects examined, although tolerance varies and death can be uncommonly slow, taking 24 h to 30 days. There is a marked absence of information on physiological processes that are affected by the pesticides, although at the cellular level they are thought to disrupt receptors for y-aminobutyric acid and glutamic acid in the central nervous system and muscular system. At high doses, treated insects are progressively immobilized, and although initially many can move when stimulated, this ability becomes lost. Some show a disturbed water balance and become distended with fluid, while others show disruption of moulting and metamorphosis. Feeding inhibition is commonly observed at sub-lethal doses. Avermectins affect many aspects of reproduction including mating behaviour, egg development, oviposition and egg hatching. The possibility is raised that these diverse disturbances are not all due to disruption of neuromuscular or central nervous system synapses, and the need for work in this area is stressed. Field studies have shown ivermectin to be most valuable in eradicating insect pests of livestock, but the use of abamectin against horticultural pests has produced less impressive results. The limited work on non-target species is discussed, and attention is drawn to some possible environmental consequences of excreted ivermectin on dung-breeding insects.

The dynamics of migration of the parasitoids Aphidius spp. between grassland and cereal fields of varying sowing dates was investigated in southern England in 1980 and 1981. Using baffled water traps, direct evidence of migration of A. rhopalosiphi De Stefani Perez females from grassland to winter wheat was obtained in June 1980, suggesting that the early-maturing grassland aphid Metopolophium festucae (Theobald) can act as a reservoir of cereal aphid parasitoids. In 1981, estimates of parasitoid production in cereal fields containing the aphids Sitobion avenae (F.), M. dirhodum (Walker) and Rhopalosiphum padi (L.) were compared with actual numbers to calculate net immigration and emigration. Barley and early-sown wheat (drilled before 14 October) proved to be significant sources of Aphidius spp., with one wheat field generating sufficient parasitoids in May to account for immigration into about 25 late-sown fields. Parasitoid migration as larvae inside aphid alatae was apparently of considerably less significance than that by adults, which were predominantly female. The advantages of early drilling of cereals to form ‘semi perennial’ reservoirs of beneficial insects is discussed and weighed against the corresponding disadvantages, especially an increased risk of barley yellow dwarf virus (BYDV).

The curculionid Cyrtobagous salviniae Calder & Sands and the pyralid Samea multiplicalis Guenée were released in north-eastern Australia for the biological control of the floating fern Salvinia molesta. C. salviniae destroyed large areas of weed and was successful at coastal and elevated sites. At equilibrium, there was less than 1 adult/20 plants and only a few, very small plants at each site. The rate at which the weed was controlled varied with mat density. The moth did not reduce plant growth permanently at any site and did not interfere with the performance of the weevil.

Females of Musca vetustissima Walker in the first ovarian cycle and of a wide range of body size were fed a range of measured quantities of protein-rich liver exudate. For a given amount of exudate, a greater proportion of large flies than of small ones matured oocytes; for a given size of fly, the proportion that matured oocytes increased with the amount of exudate ingested. Additionally, large flies matured more oocytes on less exudate than did small flies, which had fewer ovarioles.

A survey for resistance to acaricides in Rhipicephalus appendiculatus Neumann, Amblyomma variegatum (F.), Boophilus decoloratus (Koch) and B. microplus (Canestrini) was carried out in three important cattle areas of Zambia during three consecutive rainy seasons (November-May) from 1981–82 to 1983–84 to determine the pattern and distribution of resistance to dieldrin, dimethoate, dioxathion and chlorfenvinphos. Resistance was assessed using the FAO resistance test kit. Resistance to dieldrin, dimethoate and dioxathion was found in a greater number of samples from Central and Southern Provinces than from Northern and Eastern Provinces. Relatively high resistance factors were recorded for R. appendiculatus against dimethoate (mean resistance factor (RF) 10·7 ± 3·8×) and dioxathion (mean RF 8·6 ± 1·9×). B. decoloratus from Central and Southern Provinces showed mixed responses to dieldrin and low resistance to dimethoate (mean RF 4·1 ± 2·3×) and dioxathion (6·4 ± 5·0×). Most samples of A. variegatum and B. microplus were susceptible to the four acaricides. Generally, most of the ticks tested showed high susceptibility to chlorfenvinphos.

About 130 species of parasitoids and predators are reported, most of them for the first time, to be associated directly or indirectly with the cassava pest Phenacoccus manihoti Matile-Ferrero and its parasitoid, Epidinocarsis lopezi (De Santis), newly introduced into Africa as a biological control agent. About 20 species are common. The species are grouped in 11 guilds, which include the indigenous hyperparasitoids, which originally attacked parasitoids of other mealybugs, the predators with which E. lopezi competes for the same food source and their antagonists.

The seasonal abundance, biting cycle, age composition and survival of females of Aedes polynesiensis Marks and A. samoanus (Grünberg), the major vectors of subperiodic bancroftian filariasis, were studied in Samoa. A. polynesiensis density was low during the high rainfall months and increased immediately following them. A. samoanus density showed no clear relation to rainfall. A. polynesiensis was active throughout the day, with peaks indoors and out at 08.00–09.00 h and 16.00–18.00 h. The nulliparous and parous populations showed similar patterns of activity. The biting cycles of 2-parous and 3- plus 4-parous females were asymmetric with time. A. samoanus was active throughout the night, with highest activity at 23.00– 01.00 h. A minor peak at 19.00–20.00 h was more pronounced among older females than among younger ones. Night biting by A. polynesiensis and day biting by A. samoanus were rare. The parous proportion of A. polynesiensis ranged from 36·3 to 59·5% and the epidemiologically significant 3- plus 4-parous proportion ranged from 1·0 to 6·7%. The parous proportion of A. samoanus was 37·9–49·7% and the 3- plus 4-parous proportion 1·4–2·6%. The proportions found to be parous in both vectors were generally higher in the cool than the warm season, suggesting higher daily survival during that period.

The larval instars of Calliphora croceipalpis Jaennicke are described, and keys to the separation of this species from other African Calliphora species given. A key to the third instars of all genera of Calliphoridae known to breed in carrion in Africa is also provided.

The significance of morphological variation within the Thrips hawaiiensis (Morgan) species-group is examined. Multivariate analyses of four characters from 344 females and seven characters from 90 males show two distinct groups found throughout the Oriental, Pacific and American Regions, corresponding to T. hawaiiensis and T. florum Schmutz, and an intermediate group, exilicornis Hood, from Africa. The results are compared with previously published morphometric data concerning the separation of T. hawaiiensis and T. florum, and additional distinguishing characteristics are assessed. The distributions of the three forms as recognized in this study are summarized.

Viviparae of Sitobion avenae (F.) in clip-cages on winter wheat in field plots in southern England were monitored throughout the 1980–81 winter to determine characteristics of development, reproduction and lifespan under winter conditions. Rate-temperature relationships for development and reproduction were well described by straight lines when temperatures were measured above 3°C. A simple thermal-time scale could therefore be used for both processes. The parental morph and the time of year modified thermal-time requirements for the production of an adult's first 20 nymphs but did not affect those for development. For both alatae and apterae, nymph production per day-degree was greater than at higher temperatures and the relationship between reproductive rate and age was different. The minimum temperature experienced by the aphids was −7°C; survival was good, with little low temperature mortality. Total fecundity of apterae was usually greater than at higher temperatures, though some apterae and alatae that were deposited in October had low fecundity, possibly because they were insufficiently acclimatized at the onset of cold winter weather. Overwintering alatae had lower development rates, reproductive rates and total fecundity than apterae and did not survive as long, but were restless as young adults and appeared ready to migrate. Oviparae were produced from late September to mid-October but not after this, suggesting that the clone used could ‘switch off’ sexual morph production in winter.

An electrophoretic method for the study of enzyme variation, which uses cellulose acetate sheets with an agar overlay for staining, the use of a very good general purpose buffer (citric-aminopropyldiethanol amine) and the use of sodium azide as a bacteriocide to allow long term storage of chemicals as solutions are described. Tests are reported of the technique on Tetranychus urticae Koch, Aedes aegypti (L.) and several species of Drosophila. The results demonstrate that the technique offers sensitivity equal to or greater than starch or polyacrylamide gel electrophoresis and that it is applicable to very small organisms, allowing either the testing of single individuals for large numbers of enzymes or the testing of fewer enzymes under different electrophoretic conditions (i.e. to detect cryptic variation under a single condition). The technique is efficient of time and materials, and safer than conventional methods.

Holocyclic populations of aphids of the Chaetosiphon (Pentatrichopus) fragaefolii (Cockerell) group from Fragaria in British Columbia were found to have a homozygous 2n = 12 female karyotype, whereas samples from predominantly anholocyclic populations in Oregon, California, England and New Zealand have 13, 14, 15 or 17 chromosomes showing various degrees of structural heterozygosity. The 17-chromosome form is a morphologically recognizable taxon, C. jacobi Hille Ris Lambers. The other karyotypes apparently represent a series of parthenogenetic lineages derived from the 2n = 12 holocyclic form and carrying one, two or three autosome dissociations. The North American populations showed no correlation between karyotype and the number of submarginal setae, a character previously used in attempts to differentiate taxa within this species complex in western North America. Submarginal setal number varied greatly within and between clones and tended to increase in successive generations from the fundatrix, confirming that this character varies both genetically and seasonally and has little taxonomic value. Populations of the fragaefolii group from Rosa spp. in North America have a shorter rostrum than those from Fragaria. The name C. thomasi Hille Ris Lambers is assigned to this rose-feeding species, which is holocyclic on R. rugosa in British Columbia and colonizes Potentilla spp. (but apparently not P. anserina) as alternative hosts. Old World populations on Fragaria, presumably originating from North America, have longer siphunculi than North American populations of fragaefolii and few or no submarginal setae; these differences are probably due to founder effects. Both Old and New World populations of fragaefolii use P. anserina as an alternative host-plant.

Diapause development in Contarinia sorghicola (Coquillett) was found to be favoured by temperatures in the range 23–30°C. Higher temperatures (30–35°C) were suboptimal, while diapause development proceeded much more slowly at lower temperatures (5–20°C). The rate of diapause development was linear, and no minimum threshold development temperature could be established from the range of temperatures studied (lowest 5°C). The period from diapause initiation to emergence (diapause development requirement plus a 2·5-week post-diapause development requirement) was predicted to be 6 months at 27°C and 7·5 months at 23°C. It is suggested that C. sorghicola probably evolved a diapause stage in response to the absence of its host-plant during the long dry season of the African savanna region. The possibility of strains with differential diapause reactions is raised. Sex ratios favoured females slightly.

The mid-winter development, reproduction and survival of field-acclimatized viviparae of Sitobion avenae (F.) and Rhopalosiphum padi (L.) on leaves of tillering wheat and perennial ryegrass (Lolium perenne) plants at similar growth stages were compared by monitoring batches of aphids in clip-cages in field plots in southern England. For both aphid species, survival, total fecundity and reproductive rate were much higher on wheat than on L. perenne, and on both host-plants they were much higher for S. avenae than for R. padi. Development times (in day-degrees) were longer on L. perenne than on wheat, and on both host-plants were longer for R. padi than for S. avenae, though these differences were less marked. Comparison of the results with those of earlier studies suggests that large changes in cereal aphid performance occur between summer and winter and that these are both aphid-specific and host-plant-specific.

In previous laboratory studies, it was demonstrated that baldcypress (Taxodium distichum) diets eliminated a critical gut protozoan, Pseudotrichonympha grassii, from Coptotermes formosanus Shiraki. The present authors surveyed field colonies of C. formosanus confined within baldcypress trees growing in a river in Louisiana and found P. grassii was present. Termites inhabiting baldcypress trees preferred pine (Pinus) and rejected baldcypress in choice tests in the field. Significantly more termites were recruited to baits when twice as much pine was offered, indicating that C. formosanus adjusted its foraging response to resource amount. In laboratory tests, sound baldcypress sapwood and heartwood depressed survival and gut protozoan counts in C. formosanus, but baldcypress infected with the basidiomycete fungus Rigidoporus sp. and an unidentified imperfect species was favourable for the termites and their symbionts. These results suggest an important role for microbial modification in termite host selection.

Females of Glossina palpalis palpalis (Robineau-Desvoidy) caught in Nigeria were treated topically with acetone or different doses of insecticides. None was fed after treatment. Flies later larvipositing were considered to have been pregnant and those neither aborting nor larvipositing as nonpregnant. Pregnant flies were 1·3 times as heavy as non-pregnant ones. Relative tolerances were assessed by comparing LD50s. For organochlorines (DDT, dieldrin and endosulfan), pregnant females were 2·5—4 times as tolerant as non-pregnant ones, doubtless due to diversion of insecticideinto lipid-rich larval food during late pregnancy. Data for pregnant flies did not indicate any increased tolerance of organophosphates (malathion, fenitrothion, tetrachlorvinphos and pirimiphos-methyl), possibly due to the low lipid solubility of these insecticides.Pregnant and non-pregnant females were equally tolerant of the pyrethroid Sumithrin ((lR)-cis-trans-isomer of phenothrin); accelerated larviposition prevented diversion of insecticide into in utero larvae. Pregnant females were 2·6 times as tolerant of tetramethrin (pyrethroid) as non-pregnant ones. Twenty-five per cent, of flies treated with acetone or low insecticide-doses larviposited, but the results indicated that larviposition was inhibited by high doses of most insecticides, which killed before larviposition, and, noticeably, by intermediate doses of some pyrethroids (fenvalerate, permethrin and deltamethrin), probably causing prolonged paralysis of uterine and larval muscles. The results did not indicate there was raised tolerance of fenvalerate, permethrin or deltamethrin among pregnant females, but calculations including assumed pregnant ones (unrecognized due to inhibited larvipositions) suggested that pregnant females were 2·5–5·5 times as tolerantas non-pregnant ones. Other investigations showed that flies surviving for several days after treatment with pyrethroids can feed and thrive; if this allows time for the reversalof delayed larviposition, then pregnant females could be significantly more tolerant of some pyrethroids than non-pregnant ones.

A method of calculating survival rates and population size from mark-recapture experiments for bait-caught haematophagous insects is presented. The method fits the data to a series of simultaneous equations. This procedure is not affected by the cyclical nature of the recapture rate experienced in this type of experiment. Methods are presented which allow estimates of the confidence limits on the estimated parameters. Unlike earlier methods based upon a regression analysis of the log (number recaptured), this method allows estimates of the population size in addition to the survival and length of the feeding cycle of the mosquitoes. The methods have been applied to data collected in Papua New Guinea and give estimates of the total number of Anopheles feeding per night in different villages ranging from 3000 to 46 000.

Adults of Strategus aloeus (L.) were shown to be capable of supporting Baculovirus oryctes replication. This was confirmed by serology and by restriction endonuclease analysis. Although bioassays were not performed, the quantity of virus produced was similar to that produced in Oryctes rhinoceros (L.) and should encourage further trials on the potential of this virus to control S. aloeus. Scapanes australis (Boisduval) and Papuana biroi Endrödi did not support adequate virus replication. Previous findings on the susceptibility of O. monoceros (Olivier) were confirmed.