Larval responses of Delia radicum (Linnaeus), D. floralis (Fallén) and D. antiqua (Meigen) to plant volatiles were measured using a behavioural assay. Larvae were attracted to their host-plant, but non host-plants either had no effect or were repellent. Testing of individual secondary plant volatiles indicated that larvae were attracted to secondary plant volatiles from their host-plant, but were neither attracted nor repelled by secondary plant volatiles from non host-plants. A general plant volatile did not have this effect.

Avermectins administered to cattle for control of parasitic infections by injection or slow-release bolus are excreted in the faeces and have a variety of harmful effects upon Diptera and Coleoptera that develop in cow-pats: these effects are reviewed. Diptera Cyclorrhapha are severely affected, the extent of the response depending on the drug concentration in the dung. At high levels, larvae are killed or paralysed while at lower levels their metamorphosis is inhibited. At very low levels, adult emergence is reduced and a significant number of imagines show morphological abnormalities. These responses are induced by concentrations of avermectins well below levels occurring in faeces after routine treatment. Diptera Nematocera are less sensitive than Cyclorrhapha but larval and pupal development are affected at higher dose levels. Larval dung beetles and some immature adults cannot survive in the pats of recently dosed livestock. Mature adult beetles are more resistant, but contact with treated dung leads to impaired reproduction. Dung eliminated up to 5 weeks after cattle have been treated with a single injection or up to 14 days after topical dosing shows harmful activity against dung insects, and ivermectin-containing pats retain much of their toxicity after several weeks exposure on pastureland. The impact on dung insects is more pronounced and of longer duration when ivermectin is delivered daily at 40 μg per kg cow by sustained-release bolus. Following topical or injection treatments, the rate of cow-pat degradation (measured by actual loss of biomass) is significantly delayed. When cattle are treated with a bolus delivering 40 mg ivermectin per kg cow per day, their dung remains intact on grassland for at least three months. The conclusions drawn from the various papers on these effects are compared and contrasted. In particular, attention is drawn to the general failure to recognize the importance of delayed reactions to non-lethal doses of avermectins, and to our lack of consideration of long-term consequences for cow-pat insects and the wider implications for ecology.

This paper presents the first report on the sublethal effect of an insect growth regulator (IGR), hexaflumuron, on the feeding behaviour of vector mosquitoes, Culex quinquefasciatus Say, Aedes aegypti (Linnaeus) and Anopheles stephensi Liston. Percentage engorgement and feeding behaviour of the adults of the three species emerged after sublethal exposures at the larval and pupal stages were markedly affected. Depression in blood feeding was significantly higher in Aedes aegypti with lower blood engorgement ratio. The proportion of females that failed to take a blood meal was higher in A. aegypti (30.2%) than in the other species when pupae had been exposed to 0.05 mg/1 hexaflumuron. Depression in blood feeding was probably due to abnormalities in the functioning of the mouth parts and feeding behaviour. No adverse effect on the feeding activity was noticed in the F1 generation of the treated species.

Population densities of male and female Musca vetustissima Walker were estimated from recapture rates of marked flies in baited fly traps. Marked flies of laboratory and field origin were equally trappable. Trap catches of field flies were also compared with net catches for which the human collector was the source of attraction, and relationships are presented for estimating population densities based on both sampling methods. Estimates of fly density from trap and net catches at fixed locations have similar precision, coefficients of variation being approximately 55% for both males and females of M. vetustissima. Comparison of estimated fly densities (flies/ha) and annoyance indices, estimated numbers of flies approaching a collector each minute at 29.5°C, in ‘good’ and ‘bad’ fly years suggests that M. vetustissima is a potential nuisance whenever population densities exceed 1000 flies/ha.

The potential distribution of the South African weevil, Perapion antiquum (Gyllenhal), a biological control agent for the weeds Emex spp., was deter mined by the computer program CLIMEX, using its native distribution, phenology and abundance together with development parameters. The predicted distribution included parts of Hawaii where the weevil successfully controlled Emex australis and E. spinosa. In Australia, sites of past unsuccessful releases have climates that this analysis indicates are unsuitable for the insect. The most favourable regions for establishment of the weevil are near the coast in the southern half of Australia, but most of these do not overlap with regions where Emex spp. are a problem. In western Cape Province, South Africa, E. australis plants are abundant and the weevil attacks the plant after seeds have formed. In Hawaii, a fortuitous combination of climatic conditions favours the weevil during the period after seed germination, and this may be the key to its control of the weed. Sites with climatic conditions similar to successful control sites in Hawaii are not found in Australia. It was concluded that P. antiquum will be of limited use as a biological control agent in Australia even in areas suitable for its establishment.

The taxonomic identity and synonymy of four serious fruit fly pests, one of olives in Europe, and three Oriental species, two associated with citrus fruits and one with cucurbit fruits and vegetable, is clarified. Polistomimetes Enderlein is a new synonym of Tetradacus Miyake, which was originally described as a subgenus of Dacus, but is newly placed as a subgenus of Bactrocera. Heterodaculus Hardy is removed from synonymy with Polistomimetes. Mellesis citri Chen is a new synonym of B. minax (Enderlein); D. cheni Chao is a new synonym of B. tsuneonis (Miyake); and D. nubilus Hendel is replaced in synonymy with B. tau (Walker). Callantra splendida Perkins and D. discipennis Walker are transferred to the genus Bactrocera Macquart. The limits of the subgenera B. (Daculus) and B. (Tetradacus) are discussed; it is concluded that oviscape form separates those subgenera. B. (Daculus) includes the olive fly, B. oleae (Gmelin) and B. (Tetradacus) includes the Oriental citrus flies, B. minax (Enderlein) and B. tsuneonis (Miyake), plus three other species. It is also concluded that the presence or absence of anterior supra-alar setae and prescutellar acrostichal seatae should not be used in the diagnosis of Bactrocera subgenera. A lectotype of Polistomimetes minax Enderlein is designated.

The number of male tobacco budworm, Heliothis virescens (Fabricius), trapped on a daily basis in pheromone traps in individual cotton fields was compared to male and female adult densities measured by nocturnal field sampling. The decline of trap efficiency with increasing female density was demonstrated. A simple relationship for estimating H. virescens male density from the numbers trapped was derived as P♂ = (E2/13)2, where P♂ is density and E2 is the two-day exponential average of number trapped. The standard error for the regression translates to an accuracy ratio of 2:1. The results compare favourably with previous research using mark-release-recapture methodology. Application of the formula is discussed.

As the tsetse fly, Glossina morsitans morsitans Westwood extricates itself from the puparium and moves upward through the soil the ptilinum expands and contracts rhythmically and thus generates a stereotypic behavioural pattern that persists for up to 10 h if the tsetse fly remains confined. The response, which is easily recorded tensometrically from the movements of the ptilinum, can be exploited as a tool for evaluating the behavioral response of tsetse flies to various neurotoxic agents. The behavioural assay proves useful in providing precise information about the latency of the response and lethal time, and can suggest likely modes of action. For example, sublethal doses of pyrethroids reversibly suppressed the contraction cycles, a response consistent with the peripheral action of this insecticide. In contrast, chlorinated hydrocarbons greatly increased contraction frequency, a result consistent with the action of these agents on the central nervous system (CNS). Assays utilizing eight commercial insecticide preparations (Pybuthrin, K-othrin, Vaztak, Reldan, Safrotin, Acetellic, DDVP, Antrix) demonstrate the utility of this method for detecting subtle perturbations of the CNS and neuromuscular system.

Phenotypic and genotypic variation was investigated between biotype E clones of the greenbug, Schizaphis graminum (Rondani). S. graminum was collected from wheat and sorghum fields in seven Kansas counties, USA. Colonies representing single maternal lineages (clones) were initiated and maintained in an insectary, and were verified as biotype E. An allozyme survey among clones did not detect any polymorphism at 24 enzymatic loci. We were unable to detect interclonal variation for nymphal survivorship, age at first reproduction, fecundity, and reproductive lifespan. Variation among genetically homogeneous daughters within clones was as great as variation among different clones for the above parameters, due to microenvironmental effects. However, by using the intergenic spacer in the rDNA cistron as a molecular fingerprinting tool, we identified 56 unique maternal lineages among 61 clones tested. The length of the intergenic spacer varied within individual S. graminum, and different maternal lineages had unique sets of spacer sizes. However, S. graminum within a single clone shared the same sets of spacer sizes. Extensive molecular genetic variation was found among biotype E clones, despite a lack of variation in additive genetic traits. Thus, biotype E populations are made up of many genetically distinct clones and do not represent an asexual proliferation of one or a few maternal lineages.

Biconical, F3, and wind oriented (WOT) traps, and black cloth targets, baited with the odour attractant swormlure-4, were assessed as catching and killing devices for the New World screwworm fly, Cochliomyia hominivorax (Coquerel), in Mexico. Among the traps, the WOT was significantly better than the others, with a mean catch 2.7 and 86.4 times better than those of the biconical and F3, respectively. Release of swormlure-4 could be reduced from the standard 10 ml'day to 2 ml'day without a reduction in the numbers caught in a WOT. Use of electric nets demonstrated that a large visual target was not necessary for the precise location of a swormlure-4 source by C. hominivorax. Target colour was important with respect to the landing response on targets: in a two-choice situation, flies landed much more frequently on black than on blue or yellow, and more on these two colours than they did on white. C. hominivorax tend not to circle a target before landing on it: about 75% of the flies caught on a combination of electrified black target plus electric flanking net were caught on the target. The potential for use of insecticide-impregnated cloth targets in suppression of adult C. hominivorax is discussed.

Iridomyrmex humilis (Mayr) and some other ants, through preference, efficient foraging and recruitment, quickly removed artificially exposed batches of insect eggs including those of the serious pest of eucalyptus, Phoracantha semipunctata (Fabricius). This supports evidence of the importance of some ants as predators of the many insects that lay freely exposed eggs. However, P. semipunctata normally lays eggs in peeling bark crevices where the approximately 60% laid within gaps less than ca. 0.65 mm wide could not be reached even by small ants such as I. humilis and Pheidole pallidula (Nyland-er). In tree trunks, which can become heavily infested after felling, egg predation by ants seems unimportant compared with the later large mortality of competing larvae, so, egg predation cannot account for the observed striking positive correlation between presence of I. humilis and lack of Phoracantha semipunctata damage to standing trees. Egg predation and other effects of I. humilis may be more important on living trees which are attacked initially by relatively few P. semipunctata. This needs more detailed investigation as do the overall egg predatory roles of ant species in biological control.