Tetrastichus hagenowii (Ratz.) and T. asthenogmus (Wtstn.) are parasitic in cockroach oothecae and may themselves be attacked by a species of Tetrastichus of the group of T. miser (Nees). In Bangalore in 1976–79, the primary parasites were reared from oothecae of Periplaneta americana (L.), P. australasiae (F.) and P. brunnea Burm., and laboratory colonies of them were established on oothecae of P. americana. The hyperparasite, reared from field-collected oothecae of Periplaneta spp., was bred in the laboratory on oothecae of P. americana containing larvae of T. hagenowü. The immature stages of the three species of parasites were compared and their biologies studied. The eggs of the three species can be differentiated on the basis of their shape as can the pupae, but the larvae of the two primary parasites are indistinguishable. The duration of the developmental stages of the three species overlapped but the hyperparasite had a slightly shorter pupal period. Host finding by the T. hagenowii female was investigated. The two primary parasites were similar in most of their biological attributes. However, T. asthenogmus was inherently superior to the Bangalore strain of T. hagenowii in having lower levels of female sterility and its greater preference for the oothecae of P. brunnea, the predominant species of cockroach in Bangalore. T. hagenowii proved to be more tolerent of low temperatures than T. asthenogmus. The hyperparasite had an advantage over the other two species in possessing longer life-span and synovigenic females, and individual females parasitised more oothecae in their life-span than the primary parasites; but it was unable to distinguish healthy oothecae from those containing larvae of the other two species until it had drilled into them.

The effect of excluding the night-flying dung fauna, which included one abundant species of dung beetle (Scarabaeidae) in each of two areas, on the numbers of Musca vetustissima Wlk. emerging from cattle dung pads was studied in south-western Australia. Fresh dung pads were exposed to natural, daytime oviposition by M. vetustissima and half were covered at night. A test at one site before dung beetles emerged showed no effect of other nocturnal fauna on fly survival. In three experiments where Onthophagus ferox Har. was excluded, the numbers of flies emerging increased from 679 to 1019 per dung pad. In five experiments where Onitis alexis Klug was excluded, the number of flies emerging increased from 14 to 33 per dung pad. The mortality contributed by Onthophagus ferox was estimated to be around 27% and that by Onitis alexis around 15%.

Widespread slight pyrethroid-resistance in Musca domestica L. on animal farms in southern England was correlated with strong resistance to trichlorphon and to malathion, and with the presence of an esterase, E0·39, detected by electrophoresis. In the laboratory, the frequency of E0·39 increased in response to selection with either pyrethroids or trichlorphon. Genetic analysis confirmed that this esterase, controlled by a gene on autosome 2, was closely linked with moderate resistance to trichlorphon and malathion and weak resistance to pyrethroids. When autosome 2 with the gene for E0·39 was introduced into a strain homozygous for the resistance mechanism super-kdr, resistance to pyrethroids increased by a factor equivalent to the weak resistance conferred by autosome 2 with E0·39 alone. Homozygosity for both mechanisms of resistance, and E0·39, was obtained by selecting the progeny of this cross with permethrin alone, permethrin and trichlorphon, or DDT and trichlorphon, demonstrating that very strong pyrethroid resistance can be achieved through the use of non-pyrethroid insecticides. E0·39 was absent from insecticide-resistant strains of M. domestica from Denmark but was present in several multi-resistant strains from other European countries.

Wavelength dispersive X-ray fluorescence spectrometry was used to make quantitative determinations of the elemental composition of adults of Noctua pronuba (L.) that had been reared on eight soil-plant combinations and a semi-synthetic diet. There were two host-plants, beans and lettuce, each grown in two clay soils of different acidity, a sand and a commercial potting compost. Analyses were done for fifteen elements: K, P, S, Mg, Ca, Cl, Zn, Si, Al, Fe, Cu, Mn, Ni, Cr and Ti. Two groups of elements were distinguished; the first six, or major elements, each with an average content about equal to or more than 1000 μg/g, and the last nine, or minor elements, each with an average content of <1000 μg/g. The second group was subdivided into four, Zn, Si, Al, Fe, each with an average content of >100 μg/g and four, Cu, Mn, Ni, Cr, of <100 μg/g; Ti was of erratic occurrence and was excluded from most statistical analyses. When all elements in all soil-plant combinations were considered, principal components analyses showed no distinction between insects reared on any soil-plant combination, probably because of interactions between host-plants and soils. When data were grouped into two host-plant subsets and only the major elements were analysed, soils were separable within each host-plant subset. In each case, the two clay soils were clearly separable from the other two soils but not from each other. In both host-plant subsets, sexes were distinguishable by a consistently higher K content in males. No clear separations were evident in either host-plant subset when all eight minor elements were considered or when these were separated into two further groups. This work indicates that (i) characteristic elemental compositions, or chemoprints, are present in N. pronuba; (ii) choice, not necessarily number, of elements is likely to be critical in describing and interpreting chemoprints; (iii) chemoprinting is unlikely to enable sources of populations to be identified in polyphagous species like N. pronuba; and (iv) the environmentally linked variation in chemical composition, affecting biologically essential elements, may have important consequences in the population dynamics of migratory and parthenogenetic species.

Phorodon humuli (Schr.) was obtained from both wild and cultivated hop plants, cultured, and bioassayed using seven different foliar spray insecticides, and the results were assesssed by probit analysis to determine LC50s and LC95s. The wild aphids and their progeny were highly susceptible to the insecticides, whereas those from cultivated hops were generally resistant to them. The level of resistance was related to the source of the original aphid population and the insecticide used. Clones of insecticide-resistant and susceptible aphids were maintained under identical conditions, and individual adult apterae were assayed for total esterase and esterase isoenzyme activities. Total esterase activity was appreciably higher in resistant aphids than in susceptible ones. Resistant aphids were associated with high esterase isoenzyme activity of complex bands II–V, while in susceptible aphids these bands were virtually missing. An insecticide-resistant clone of P. humuli was selected for low esterase activity and a susceptible clone was selected for high esterase activity, over eight generations. Selection pressure was then reversed for a further eight generations. The resistant clone lost its esterase activity by generation six and it remained low thereafter, whereas that of the control stock remained high. By contrast, the esterase activity of the susceptible clone remained unaltered by selection. The resistant clone also lost its resistance to both methomyl and methidathion.

In studies in Nigeria, all instars of Zonocerus variegatus (L.) were found to be strongly attracted to flowers of the common exotic composite weed Chromolaena odorata. Experiments in the field and with caged nymphs suggested that the attraction is due to a volatile compound(s) concentrated in the conspicuous stigmas and released when the buds open. Although very palatable, the flowers seemed inadequate as food, and most of the nymphs roosting on C. odorata even during the flowering season had fed on leaves of C. odorata or other plants. Feeding diminished the attraction to the inflorescences in experimental cages, and of the field nymphs attracted between 11.00 and 15.00 h, a significantly higher proportion than on other plants had relatively empty foreguts. The numbers of field nymphs attracted were maximal at 08.00–10.00h and minimal at 11.00–12.00 h. Both in the cages and in the field, interest in the inflorescences diminished after about 17.00 h, when the highest points within reach are being looked for as roosting sites. Reduction of C. odorata around plantations is unlikely to lessen crop damage by Z. variegatus, but insecticides for Z. variegatus control could be applied conveniently to the tops of C. odorata at roosting time during the flowering season.

Sitona discoideus Gylh., an introduced pest of lucerne in New Zealand, exhibits univoltine, aestivatory seasonality in Canterbury and Otago, with each generation appearing in late December. Some two weeks after the December emergence of adults, flights to aestivation sites commenced. These sites were commonly remote from the lucerne stands and included such places as under stones or at the base of trees, fence posts, etc. At the commencement of aestivation, the indirect flight muscles atrophied rapidly, only to redevelop some 6–8 weeks later when autumnal post-aestivatory return flights to lucerne began. During the winter, S. discoideus fed on lucerne foliage and became reproductively mature. By October, age-related adult mortality had begun, and for about two weeks in December no adult weevils were present at all in one Canterbury site. In Otago, there was a distinct generation overlap of 2–3 weeks. The eclosion of new generation weevils was closely synchronised; it is suggested that this may have been the product of differential egg development and egg-laying temperature thresholds and a high fourth instar and pupal develoment threshold. Synchronised emergence of adults tended to accentuate the problem of defoliation caused by their feeding.

A non-technical description is given of a new, powerful, low cost field system (Infra-red Active Determination of Insect Flight Trajectories or IRADIT) for detailed and automatic remote sensing studies of natural insect flight behaviour. The special requirements and difficulties of the detection problem are defined. A series of examples of field devices and techniques are presented to illustrate the key factors of the optical sensing and tracking of insects in flight. In the finally adopted IRADIT system, flying insects are differentially illuminated, under all natural light conditions, by an intense beam of pulsed near-infra-red radiation and detected using a shuttered image intensifier linked with a video camera operating at a rate of 50 frames per second. Immediate fully-automatic determination of the flight trajectories of several simultaneously detected insects was achieved, at this same high rate and in the presence of sky background photon noise, by processing the video signals with electronic circuits and a microcomputer. Flight trajectories are influenced by the local wind, whose vector must be subtracted to study insect flight behaviour. This was achieved by the use of a specially developed sensitive three-vector vane anemometer, providing digital data to the microcomputer at a minimum rate of 5 Hz. In tests of the prototype IRADIT-anemometer system in the field, insects with wing area of only 1·5 mm2 and flying against the midday sky were readily tracked at ranges up to 15 m. A range of at least 100 m is expected for nocturnal moth tracking.

An account is given of changes in nocturnal illumination at the spring and autumn equinoxes and summer and winter solstices at latitudes between 50 and 60°N. A Relative Trap Index (RTI) was devised to describe changes in light-trap effectiveness and used to adjust catches of Noctuidae and Geometridae for change in trap effectiveness caused by seasonal and latitudinal change in nocturnal illumination at latitudes between 50 and 58°N. When so adjusted, catches were frequently larger in northern than in southern latitudes, not smaller as unadjusted catches show. It is clear that unless light-trap catches are adjusted to allow for changes of illumination, comparisons over time and space, particularly those which involve assumptions about sample constancy, are suspect. Because of the large differences in RTI that may exist between northern and southern traps, particularly in summer and between the summer solstice and other times, it may be necessary to use different light sources at different times of year to maintain a consistent trap sample.

The nature, frequency and causes of reproductive loss were investigated in populations of Glossina pallidipes Aust. in western and coastal localities in Kenya. Daily collections from biconical traps in which females were trapped for varying periods up to 30 h were followed by a series of hourly captures which gave less biased data. Ovarian abnormalities and insemination failure were rare, and abortion was the only major source of loss of fecundity. Total reproductive loss was within the range 1·60–1·97% (0·23% ovarian loss plus 1·37% abortions or 1·74% total empty uteri) in western Kenya (Lambwe Valley) and 0·99–1·71% from less comprehensive data at the coast. The incidence of empty uteri was higher in daily than in hourly collections, due mainly to premature parturitions brought about by the stressful effects of prolonged confinement in traps and handling. Abortions were significantly more frequent in females which had ovulated but were not yet parous than in older, parous flies. No relationship between the frequency of abortion and climate, tsetse density or pathogen or parasite infection could be demonstrated.

A laboratory colony of Glossina morsitans submorsitans Newst. originating from Nigeria exhibits an excess of females over males. The sex ratio distortion of more than two females to one male was studied by the maintenance of individual flies. Five males sired more than ten daughters without producing any sons when mated to several females, whilst other males fathered approximately equal numbers of male and female offspring; there was no evidence for selective abortion of male embryos. The presence of these ‘distorter’ males, which produce only female offspring, was found to cause the sex ratio distortion. The results are discussed with reference to data from the field which indicate that this genetic aberration is not confined to the laboratory; possible implications for chemical control programmes are assessed.

Crosses of Sudanese strains of Anopheles arabiensis Patt. resistant and susceptible to malathion indicated that the resistance was incompletely dominant. The results of tests of male progeny of successive backcrosses agreed well with the hypothesis of control of the resistance by a single gene. However, the results from females suggested the additional involvement of a sex-limited modifier. Tests of mixtures initiated with a 1:1 ratio of resistant and susceptible first-instar larvae gave little evidence for selective mortality during the larval stage. However, the mortalities in tests on malathion recorded among adults emerging on successive days from these mixtures, and also from F2 and backcross progenies, indicated that the development of the resistant larvae was significantly faster than that of the susceptible ones. The fact that this occurred in the F2 and backcross progenies indicates that it may be due to a pleiotropic effect of the resistance gene, but it is pointed out that results from much more prolonged backcrossing would be necessary to rule out the possible effects of linked genes.

Field studies were carried out between 1974 and 1978 on the hispine Uroplata lantanae Buzzi & Winder which feeds on Lantana tiliaefolia plants under shade in temperate climate areas of Paraná State, southern Brazil. The life-cycle from egg to adult took 48–54 days between October and January with only one generation a year. Adults fed by rasping leaves and larvae mined leaves, occasionally destroying up to 24% on individual plants. Adults colonised tall plants preferentially and chose to oviposit on the higher branches, which suffered significantly less leaf abscission. Greater numbers of all stages of the hispine were found on lantana plants around which a plant-free zone was created compared with those growing amongst other understorey plants. Larvae were parasitised by a complex of braconid, eulophid, chalcid and torymid parasitoids, with greater parasitisation occurring at lower branch heights. Multiple-choice host-specificity tests and field observations showed that U. lantanae fed only on L. tiliaefolia and L. camara. The effectiveness of U. lantanae as a biological control agent of lantana in Australia is discussed.