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).

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.

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.

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.

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.

The resistance of 32 melon lines to Tetranychus cinnabarinus (Boisduval) was studied in Israel. Average counts ten days after infestation, at the fourth-leaf stage, ranged from 3·5 to 57 mites per four leaf discs 1 cm in diameter; six lines had significantly low counts, ranging from 0·9 to 1·5 mites per four leaf discs. Fourteen of the lines were also tested at the flowering stage. No mites were found on two lines, and on a third line very few mites were observed. All three lines also had had significantly low mite counts at the fourth-leaf stage. The results suggest there is a definite variation among melon lines in resistance to mite infestation.

In field populations of Lucilia cuprina (Wiedemann) in Australia, there was a very low percentage of mating in females that, on the evidence of their stage of ovarian development, had not yet consumed protein-rich material. Virtually all females whose oocytes had reached early vitellogenesis had mated. Thus, most females of this anautogenous species had mated soon after their ovarian development had proceeded beyond the resting stage at which development ceases in females that have not consumed protein. The relationship between mated status and ovarian development of hand-caught females did not differ from that for females which had been allowed to remain for more than 1 h with sexually active males in the collection chamber of traps. Thus mating occurred rarely, if at all, in the trap chambers, which suggests that females in the field mate soon after first becoming sexually receptive. This, together with knowledge that females of this species do not remate readily, indicates that the operational sex ratio in L. cuprina is heavily male-biased.

The populations of the most common aphid species on sugarbeet, and their principal predators, were monitored on insecticide-free study areas of the crop in south-eastern England in 1978–81. The peak populations of Myzus persicae (Sulzer) varied considerably in size from year to year and were related to the severity of the previous winter. Those of Aphis fabae fabae Scopoli, which occurred slightly later in the season, also varied greatly in size but were not strongly linked to winter temperatures. The sizes of the peak populations of Macrosiphum euphorbiae (Thomas) were similar each year. The annual variation in the level of infection by virus yellows reflected the peak populations of Myzus persicae and not those of the other aphid species. Coccinellids first appeared in the sugarbeet each year in mid-late June, as the aphid populations were developing, and their peak populations did not vary greatly from year to year. Syrphid larvae appeared later in the season than coccinellids, and their numbers seemed closely linked to those of A. f. fabae. Anystid mites were observed on most count dates in all years. The implications of the findings of the study for control of aphids and virus yellows are discussed.

The rate of development, fecundity and lifespan of apterae of Diuraphis noxia (Mordvilko) were determined at five sets of temperature and daylength conditions. The time required to complete pre-imaginal growth at mean daily temperatures of 10, 13, 14, 17·25 and 20°C was 19·70, 12·09, 11·25, 9·88 and 8·17 days, respectively. The threshold for development was estimated to be 0·54°C and the number of day-degrees C required to complete development was 158·73.

The morphology of the antennae, caudae and wingbuds of Diuraphis noxia (Mordvilko) was used in conjunction with ratios between antennal segment lengths to draw up a key for diagnosis of the instars.

Migration and colonization of the coconut palm by Eriophyes guerreronis (Keifer) was studied in St Lucia in the West Indies. Mites were not found in unfertilized flowers but were present within a few weeks of fertilization. Nuts remained vulnerable to colonization for a number of months, and mites were present on nuts for up to 13 months. Protection of nuts for the first few months after fertilization is of most importance. On the tree, much migration could be due to mites walking in large numbers across nut surfaces, and they could move from one inflorescence to another if the two were in contact. Increased nut damage appeared to encourage mite migration.

Spodoptera exempta (Walker), in common with several noctuid moths, exhibits a density-dependent phase polyphenism. The abdominal glyceride contents of both sexes at emergence were 2·5 to 6·1 times greater in the gregaria than in the solitaria phase moths. Abdominal and thoracic total protein levels, haemolymph total protein, glyceride and carbohydrate, and the relative quantities of tri-, di- and monoglycerides were comparable in the two forms. Weight-related fecundity was strongly influenced by larval phase. Females from solitaria larvae produced approximately half the numbers of eggs laid by those reared in crowded conditions, but this difference was only evident in moths allowed distilled water. Moths having access to sucrose laid comparable numbers of eggs, irrespective of phase. There were no differences in the levels of metabolic reserves in the eggs. Differences in glyceride content, preoviposition period, fecundity and lifespan were apparent between laboratory strains. The implications of these differences for migratory flight and reproduction in the field are discussed.

Sporadic previous reports of chironomid larvae feeding on roots of horticultural plants are reviewed and related to the growing recognition that a particular parthenogenetic species can damage severely indoor horticultural crops, particularly lettuce and young tomatoes. The taxonomy of the pest, Bryophaenocladius furcatus (Kieffer), is assessed, new synonymy proposed and a neotype and lectotype designated. The species is redescribed from the larva, pupa and adult female.

The biology of the predacious cricket Metioche vittaticollis (Stål) collected from rice in the Philippines was studied in the laboratory and greenhouse. The cricket preyed on the eggs of a range of insect pests of rice including Chilo suppressalis (Walker), Cnaphalocrocis medinalis (Guenée), Hydrellia philippina Ferino, Mythimna separata (Walker) and to a lesser extent on the eggs of Leptocorisa oratorius (F.). There was no predation on the eggs of Scirpophaga incertulas (Walker).

The effect on aphid population development of creating natural enemy refuges by spraying only alternate strips of winter wheat with the aphid-specific insecticide pirimicarb at 140 g a.i./ha was compared with those in an unsprayed and a completely sprayed block in south-eastern England. The numbers of Sitobion avenae (F.), Metopolophium dirhodum (Walker) and Rhopalosiphum padi (L.) increased rapidly in the unsprayed block and in the unsprayed strips to reach similar peak densities in early August. Natural enemy activity was similar in these two areas, indicating negligible movement of predators and parasitoids from the sprayed strips to the unsprayed strips. Instead, aphids re-colonized the sprayed strips more quickly than the sprayed block, and the peak density in the former was similar to those in the unsprayed areas.

Leafhoppers of the genus Cicadulina transmit pathogens to Gramineae (including cereals and sugarcane) in Africa, India and South America. Previous taxonomic and applied studies on Cicadulina are reviewed, and an identification key to the 22 recognizable species is given; each species is discussed and illustrated. Two species, C. dabrowskii sp. n. and C. immaculata sp. n., are described; C. anomala Van Rensburg, C. kalaharica Van Rensburg, C. inopia Van Rensburg, C. ungula Van Rensburg, C. bispinosa Van Rensburg, C. opaca Van Rensburg, C. waltersi Van Rensburg, C. scabra Van Rensburg and C. letabae Van Rensburg are established as junior synonyms of C. anestae Van Rensburg, C. bipunctella (Matsumura) as a junior synonym of C. bipunctata (Melichar) and C. triangula Ruppel as a junior synonym of C. storeyi China.

Multivariate techniques, principally the method of canonical variates, were used to investigate morphological variation within and between populations of the group of Myzus persicae (Sulzer) from North and South America, Europe, Africa and Asia. The scores on the first canonical variate of samples from tobacco in North America, the Mediterranean region, the Middle East, Africa and Sri Lanka all grouped consistently when compared with samples from other host-plants, even after aphids from tobacco had been reared for up to seven years on a non-tobacco host. Thus there is a widely-distributed tobacco-adapted form, closely related to M. persicae but with its own characteristic morphology. Morphological discriminants are given for the recognition of apterous and alate viviparae of this tobacco form, which is given the name M. nicotianae sp. n. Both M. persicae and M. nicotianae have 2n = 12, and both are frequently heterozygous for apparently the same autosomal translocation, which they must have acquired independently. M. nicotianae is presumably isolated from M. persicae by being permanently parthenogenetic. In Japan and Central Asia, however, aphids of the M. persicae group on tobacco can produce sexual morphs; the taxonomic status of these latter populations is still unclear. Multivariate comparison of European and North American populations of dark green aphids of the M. persicae group with 13 or 14 chromosomes in somatic cell nuclei instead of the normal 12, led to the conclusion that these all belong to one morphologically variable taxon, M. antirrhinii (Macchiati). Keys are provided to the apterous and alate virginoparae of the species of the M. persicae group in America.

The mortality of eggs and larvae of Musca vetustissima Walker, caused by two scarabaeine dung beetles was measured in the laboratory in favourable cattle dung at 23°C. Eggs and larvae less than one day old were the main stages killed in the dung. Mortality from beetles that entered dung immediately after fly oviposition was higher than that from beetles that entered the dung one or three days later. The results also indicated that there are differences between species of dung beetles in the mode of action against the fly. The smaller beetle species, Onthophagus binodis (Thunberg), at densities of 120 beetles/pad caused increased mortalities of 12% of fly eggs and 11% of young larvae but did not affect older larvae, while the larger species, O. ferox Harold, at densities of 48 beetles/pad caused no extra mortality of eggs but did cause an increased mortality of 47% of young fly larvae and 61% of older larvae.