The aphelinids Encarsia adrianae sp. n. and E. cibcensis sp. n. are described from material in culture ex Bemisia tabaci (Gennadius) on beans at the C·A·B International Institute of Biological Control, Ascot, UK. They are descendants of material collected in Rawalpindi, Pakistan, from B. tabaci on Lantana camara.

Two new species of Cicadulina, C. ghaurii sp. n. and C. hartmansi sp. n., are described. Both occur over a wide area in Nigeria and Cameroon, and C. ghaurii has been shown to transmit maize streak virus.

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.

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.

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.

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.

The toxicity of two pyrethroid insecticides, S-bioallethrin and cypermethrin, was investigated over time at 12, 25 and 31°C in susceptible and kdr resistant strains of Blattella germanica (L.). Both strains showed a negative temperature coefficient (i.e., greater kill with decreasing temperature) for S-bioallethrin. The susceptible strain had a negative temperature coefficient for knockdown, but a positive temperature coefficient for mortality towards cypermethrin. The resistant strain had a negative temperature coefficient towards cypermethrin at all times. Resistance to S-bioallethrin was generally greatest at 25°C initially, although the difference between temperatures and the level of resistance diminished with time. Resistance to cypermethrin was significantly less at 12°C than at 25 or 31°C.

Anopheles subpictus Grassi in Sri Lanka is under selection pressure from both agricultural and public health insecticides. Agricultural selection pressure has produced larval specific carbamate resistance which appears to be correlated with high esterase activity. High esterase activity was found in both larvae and adults, but one of the larval elevated bands was not present in the adult, and two other adult bands were not found in the larvae. Broad spectrum organophosphate resistance was found in both the larvae and the adults and was associated with an increase in mixed-function oxidase activity. There was no evidence of an altered AChE mechanism in this population.

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.

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.

Chelonus chailini sp. n., which was discovered recently during a survey of potential biocontrol agents of the cocoa pest Conopomorpha cramerella (Snellen) in Malaysia, is described and illustrated. Five other gracillariid leaf-miners and bud-borers (Acrocercops globulifera Meyrick, A. diffluella van Deventer, A. caerulea Meyrick, A. phaeospora Meyrick and Epicephala chalybacma Meyrick) are cited as hosts of C. chailini, and brief notes on its biology are given.

An automatic sticky trap for aphids which segregates each day's catch is described. The trap is driven by a mechanical clock which operates for seven days. Each day, a yellow-coloured drum covered with a sticky coated transparent cellulose acetate sheet is automatically exposed and the one for the previous day stored in a holding cylinder.

The within-plant dispersion characteristics of Megalurothrips sjostedti (Trybom) on cowpeas were determined in studies in Nigeria. Iwao's regression procedure and Taylor's power law analysis were used to determine the relationship between the mean and variance of thrips counts. Both methods showed that adult thrips were randomly distributed within cowpea plants at initial low populations. At later high densities, Iwao's method provided a better fit of the population dispersion of larvae and adults and showed that both were aggregated. The negative binomial best described this aggregation at high population densities. Sequential count plans suitable for pest management surveys were developed using critical stop lines derived from Iwao's regression procedure and Taylor's power law, but the latter was found to require less effort to achieve the same level of precision. There was a functional relationship between the variance and mean of untransformed population counts, and the suitability of transformation functions is discussed.

Adults of Dacus spp. feed on plant surface bacteria. The responses of D. tryoni (Froggatt) and D. cacuminatus (Hering) to some components of bacterial odours and to cue-lure were tested in a field-cage olfactometer, in studies in south-eastern Queensland. One component of bacterial emission, 2-butanone, attracted D. tryoni (a species responding to cue-lure) but not D. cacuminatus (a species responding to methyl eugenol) and is suggested as the attractive portion of the cue-lure molecule. Sexually mature males and immature females of D. tryoni responded to 2-butanone, cue-lure and bacterial odours in field-cage tests. Females fed on sugar and water required protein hydrolysate to produce eggs, but males were fertile with or without protein. These different nutrient requirements, and the fact that males and females possess different crop colour and bacterial contents when feeding in the same host-plant, indicate that the sexes feed on different substrates. Consequently, the strong bacterial attractant cues in the host-tree may be a feeding attractant to females and a sex attractant to males. It is proposed that 2-butanone is an important rendezvous stimulant in nature, bringing the mature male flies into the feeding and oviposition sites (host-trees) of the developing females for mating encounters.

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.

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.

Five sampling methods were evaluated for efficiency in estimating field populations of Megalurothrips sjostedti (Trybom) on cowpeas in Nigeria. The methods (sticky traps, water traps, sweep netting, shaking plants and the collection of whole plant samples) were judged on the basis of low sample variance, low cost and fidelity to absolute population trends. Shaking plants and water traps were the best sampling techniques on the basis of sample variance and cost. Shaking plants also showed the closest correlation with absolute population trends and is therefore recommended for rapid estimation of field populations of thrips. The performance of the usual alcohol method of sampling M. sjostedti on cowpeas (collecting racemes and flowers in alcohol) was not comparable with those of shaking plants and water traps, but was considered important because it sampled the infested structures, eliminating more transient visitors which might also be sampled by shaking plants.

Electrophoretic variation of eight enzymes (thirteen loci) including esterase-4 (EST-4, the enzyme conferring insecticide resistance) was studied in clones of Myzus persicae (Sulzer) from several localities in south-eastern England (major beet and rape growing areas) and from a site in mid-Scotland (a seed potato growing region). All loci except esterase-1/-2, which showed putative allelic variation with slow (EST-1) and fast (EST-2) bands, and EST-4, which occurred as three principal quantitative variants (susceptible (S), resistant (R1) and highly resistant (R2)), were found to be monomorphic. The occurrence of the insecticide-resistant variants is reported and shown to differ little from previous surveys, with frequencies of R1 aphids on rape in south-eastern England appearing close to fixation (>0·9), probably due to continued insecticide selective pressure. The general lack of qualitative (i.e. mobility) variation at the loci examined is thought to be due to the species having gone through tight population bottlenecks in the past, which have systematically eliminated the rarer alleles, driving the most common to fixation. Consequently, as the data suggest, only a small number of M. persicae genotypes may exist in Britain.

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.

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.