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.

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.

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.

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.

Field cages in southern England enclosing single rows of potatoes and infested with differing initial proportions of S (susceptible), R1 (moderately insecticide resistant) and R2 (very resistant) clones of Myzus persicae (Sulzer) were sprayed three times, at 14-day intervals, with pirimicarb (carbamate), demeton-S-methyl (organophosphorus) or a mixture of deltamethrin and heptenophos (pyrethroid and organophosphorus insecticides). The numbers of aphids on top, middle and basal leaves were counted, pre-treatment and one and eight days after each of the three sprays. The resistance genotype frequencies of the three variants were determined by an immunoplate assay which measures the amount of the carboxylesterase E4, the enzyme conferring resistance, in individual aphids. All three chemicals selected strongly for the very resistant variant. After three sprays, R2 aphid frequencies approached or equalled fixation (1·00) for both starting frequencies. However, the deltamethrin-heptenophos mixture selected for R2 aphids more rapidly than the other chemical treatments. Increasing the initial starting frequency of R2 aphids from 0·02 to 0·20 led to a more rapid increase of their frequencies towards 1·00 for all chemicals. The numbers of aphids on all treated plots were less than on the control. However, the more rapid increase in the proportion of R2's on plots treated with deltamethrin plus heptenophos, coupled with enhanced nymph production, resulted in a smaller reduction in numbers than was achieved by the other chemical treatments. The need for novel control methods is discussed in the light of the strong selection for R2 aphids exerted by all three insecticide classes.

Ecological, population and community studies of arthropod fauna inhabiting dung require large-scale quantitative data to produce statistically adequate results. A mechanized extraction technique is described which recovers fauna accurately and rapidly from large numbers of cattle dung pads. The equipment comprises a motor-driven paddle which agitates the dung sample in a bucket with fine mesh panels inlaid into its walls and through which is passed a continuous flow of water. An electric motor drives five such units simultaneously. Most dipteran puparia and adult arthropods float on water and are recovered following the washing. Puparia are recovered manually, while mites and adult beetles are extracted from the floating debris with heat in modified Berlese-Tullgren funnels. The wash bucket and its drained contents are then immersed in a flotation vat through which a sodium carbonate solution is recirculated. Insect eggs and larvae are floated off into sieves and rinsed before preservation. The resulting samples are fixed and preserved in 70% ethanol for later identification and counting. The procedure recovered 70–90% of most types and stages of dung fauna. Up to 25 complete dung pads can be processed per day with a team of three people.

An enzyme-linked immunosorbent assay (ELISA) was used to examine the digestive tracts of potential predators collected from an experimental cabbage plot in Victoria, Australia, for antigens of Pieris rapae (L.). The rabbit serum used in the study was made against an extract of all immature stages of the prey species and was shown to interact with proteins representing all immature stages. The serum was also shown not to react with antigens from other pest species collected from the experimental plot or with predators not exposed to the prey. The main predators found using the assay were the labidurids Nala lividipes (Dufour) and Labidura riparia truncata Kirby, the staphylinid Thyreocephalus cyanopterus (Erichson) and the eusparassid Olios diana (L. Koch). These results agree closely with laboratory observations on predation. The assay was sensitive, allowing 2000 assays to be performed per millilitre of serum and thus a single serum collection of 20 ml permitted about 40 000 assays.

New information on the intraseasonal progression of larval infestations of Busseola fusca (Fuller) in South Africa was obtained through repeated sampling in maize plantings of different planting dates over various seasons. Due to the occurrence of distinct periods of moth flight, variation in planting date had a marked influence on levels of larval infestation. Also, plants were found to be most attractive as sites for oviposition between three and five weeks after emergence, resulting in a definite pattern in the time distribution of different larval instars in different plant parts. In the pre-tassel stage of plant development, most larvae occurred in localized groups within the whorls, reaching maximum numbers eight weeks after plant emergence. The emergence of the tassel forced some larvae to migrate to adjacent plants, resulting in an increase of internally damaged plants without an increase in larval numbers. It is shown that scouting for eggs over a limited period of plant development can lead to better timing of spray applications and thus to more cost-effective control measures.

Hourly trap catches of Delia radicum (L.) from opposite sides of host-plant (cabbage) and non-host-plant (carrot) plots in eastern England were analysed with respect to local wind direction, wind speed, temperature and humidity. More females were caught around host- than non-host-plant plots. They predominantly approached host-plant plots by upwind movement, but equal upwind and downwind movement occurred to non-host-plant plots. A generalized linear model revealed that wind speed and humidity influenced the total trap catch of females, with wind speeds below 2 m/s and relative humidities above 65% being most favourable to fly activity, while wind speed was the only variable having a significant effect on the trap catches of flies moving upwind to host-plant plots.

In a Gambian village, the peak collections of females of the complex of Anopheles gambiae Giles occurred three months after the onset of the heaviest rains; 32% of these were A. melas Theobald, and 54% of blood-meals were identified as originating from man. Counts of A. gambiae s.l. in rooms containing permethrin-treated bed nets were compared with those in rooms containing placebo-treated nets. The numbers in the permethrin-treated nets were far lower than in placebo-treated nets. A higher rate of exophily was noted in rooms containing permethrin-treated nets. The numbers of unfed A. gambiae s.l. found inside the rooms with placebo-treated nets were significantly higher than those with permethrin-treated nets. However, the proportion fed and the mortality in the exit traps were not significantly affected by permethrin treatment. Three-minute bioassays conducted on four different fabric types impregnated at the same concentration showed that the toxicity varied between the fabrics. Handwashing severely reduced the toxicity and approximately halved the permethrin content. Bed nets are frequently washed in Gambian villages, and this could be a problem in the application of permethrin impregnation of bed nets for vector control. Methods are discussed to overcome this problem at the village level.

Laboratory bioassays with gravid females of Lucilia cuprina (Wiedemann) were used to isolate the source(s) of olfactory attractants emanating from larvae-infested media. Adults were not attracted by odours from axenic (micro-organism-free) larvae, but volatiles from xenic larvae were highly attractive. The attractants proved to be kairomones not pheromones, as odours from other species of calliphorids and a sarcophagid species were also attractive. Axenic, proteinaceous media produced a low level of attractive volatiles, which was increased by the activities of axenic larvae growing on the media. A greater degree of attraction occurred to odours from xenic media, and this too was much increased by the actions of growing larvae. The order of attractiveness of such volatiles is therefore: xenic with larvae >> xenic without larvae > axenic with larvae > axenic without larvae. It is concluded that larvae-infested media owe their great attractiveness to the volatiles produced by the action of micro-organisms, not to specific larval volatiles. Larval activity accentuates the output of attractive volatiles from both xenic and axenic proteinaceous media, possibly due to the effects of digestive enzymes, pH changes, mechanical mixing, warming or aeration or a combination of some or all of these factors.

Radioactive (32P) and genetic (recessive eye-colour mutation) markers were used to estimate egg to pupal survival of Musca vetustissima Walker. Both marking techniques provided similar survival estimates under laboratory and field conditions in Australia. Egg to pupal survival rarely exceeded 10% in samples at intervals during spring and summer. Abiotic (dung quality and weather) and biotic (other dung fauna) mortality agents were both important in limiting the breeding success of M. vetustissima, being jointly responsible for a seasonal mean mortality of 93·8%.

Examples of Chrysomphalus aonidum (L.) from which the scale covers had been removed, were about six times as sensitive to malathion as intact insects (LC50s of 0·09% and 0·55%, respectively). These results indicate that the scale cover probably absorbed part of the insecticide. Immature stages of the external parasitoid Aphytis holoxanthus DeBach on C. aonidum were not affected by 0·13% malathion applied to the host. However, adults of the parasitoid, which were extremely susceptible, were exposed before or during emergence to lethal levels of the insecticide present in the host scale cover. The findings are discussed in the light of the adverse effects of malathion-bait sprays applied against Ceratitis capitata (Wiedemann) on beneficial insects, and failures of biological control of scale pests on citrus in Israel.

Bibionid flies were sampled in grassland in Northern Ireland from 4 April to 13 June 1985 using water and sticky traps with a range of characteristics. Nearly 70 000 bibionids were taken, of which 89·5% were males. Bibio johannis (L.) accounted for 96% of the catch, the rest comprising Dilophus febrilis (L.) (3%) and D. femoratus Meigen (1%). Trapping was carried out adjacent to a hedgerow and in the centre of the field. Differences in the abundance of the flies at these two locations occurred for all three species. Yellow was the best colour for maximizing catches. Greater numbers of B. johannis (63%) were taken in water than sticky traps, but over 76% of Dilophus spp. were caught on the latter. Increasing the diameter of water traps tended to enlarge the catch (principally B. johannis), but catch per unit area was relatively constant. The height of sticky traps above the ground affected the catch of all three species, indicating different flight levels.

Investigations into feeding behaviour and activity patterns, basically by biconical trap sampling, were carried out as part of a study of the population ecology and dynamics of Glossina pallidipes Austen in the Lambwe Valley, Kenya. Host-preference determinations from blood-meal analyses showed that over 80% of feeds constantly derived from bushbuck, buffalo and bushpig, in roughly equal proportions. Activity cycles in relation to feeding and pregnancy, investigated by mark-release-recapture and physiological methods, indicated four-day feeding intervals for males and three-day ones for females. The periodicity was more variable in males, and in females was contingent upon reproductive events, with feeding mainly taking place just before the in-utero moult of the second-instar larva to the third instar, just after larviposition and again at a more variable time during pregnancy. Comparisons of nutritional status from size, weight, and fat and haematin levels showed that flies from thicket had consistently greater fat reserves than flies from Acacia woodland and conifer plantation. No seasonal differences were found, nor any relationships between other variables. Based on hourly sample data, both sexes showed unimodal diel activity patterns, but with clear differences. Activity was most closely correlated with temperature, to a lesser extent with saturation deficit and least with light intensity, and better correlations were obtained with females than males. Diel activity patterns in both sexes were also age-related, and from the close similarity found between male and virgin female activity patterns it was inferred that male activity around traps was partly sexually oriented. Using electric screens in conjunction with biconical traps, comparisons between flies attracted to traps and those actually caught showed that traps were relatively more efficient in catching males than females, but captures were representative of the active population in terms of age and pregnancy.

The identity of Phenacoccus gossypii Townsend & Cockerell is established as a local species in Mexico and southern USA. Although P. madeirensis Green was described from Madeira and is recorded from much of the African mainland, it was probably introduced from tropical America. It is now known to be common on many crop and ornamental plants in North and South America where it has often been mistaken for P. gossypii. Both species are redescribed and illustrated, and their range of variation is discussed. P. grenadensis Green & Laing and P. harbisoni Peterson are synonymized with P. madeirensis. A related species, P. baccharidis sp. n., is described from Brazil, and P. sphaeralceae sp. n. is described from Arizona. P. hurdi McKenzie is redescribed and is now recorded from an extensive area in southern USA and Mexico. All five species have numerous dorsal multilocular pores and are included in a key to 15 related species in North and South America.