For the first 150 years following their introduction, eucalypts planted in the California landscape were free of both insect pests and diseases. In the last 15 years, numerous herbivorous insect species have been introduced accidentally into the State and have caused significant damage to the trees. Several of these species, e.g. Phoracantha semipunctata (Fabricius), Phoracantha recurva Newman (Coleoptera: Cerambycidae) and Gonipterus scutellatus Gyllenhal (Coleoptera: Curculionidae), have also been introduced into other parts of the world where eucalypts are grown, whereas others, e.g. Glycaspsis brimblecombei Moore (Hemiptera: Spondyliaspidae) and Eucalyptolyma maideni Froggatt (Hemiptera: Spondyliaspidae), are currently restricted to California and Australia. Research programmes have provided management solutions to individual pest problems, but as more pest species are introduced, these solutions must be integrated across broad geographic, horticultural, and economic scales, in a systems approach.

Temperature tolerance was investigated in nine populations of Plutella xylostellaLinnaeus from tropical and temperate regions of Asia. At all rearing temperatures between 15 and 35°C, no clear differences were observed in female egg production or larval development between tropical and temperate populations. Thus, tropical populations did not show a high-temperature tolerance superior to that of the temperate populations. In all populations, the net reproductive rate (number of new females born per female) largely depended on the number of eggs laid per female, and egg production significantly decreased with increasing temperature (P < 0.001). Larval developmental rate also showed a significant positive correlation with temperature (P < 0.001). Per cent hatch of eggs and larval survival did not show a significant correlation with temperature: hatching was constant between 15 and 32.5°C, but considerably lower at 35°C. Larval survival was similar between 15 and 30°C, appreciably lower at 32.5°C and declined to 0% at 35°C. Based on these results, environmental conditions under which P. xylostella can maintain a high population density throughout the year in tropical and subtropical regions are discussed.

The continuous operation of insect-monitoring radars in the UK has permitted, for the first time, the characterization of various phenomena associated with high-altitude migration of large insects over this part of northern Europe. Previous studies have taken a case-study approach, concentrating on a small number of nights of particular interest. Here, combining data from two radars, and from an extensive suction- and light-trapping network, we have undertaken a more systematic, longer-term study of diel flight periodicity and vertical distribution of macro-insects in the atmosphere. Firstly, we identify general features of insect abundance and stratification, occurring during the 24-hour cycle, which emerge from four years' aggregated radar data for the summer months in southern Britain. These features include mass emigrations at dusk and, to a lesser extent, at dawn and daytime concentrations associated with thermal convection. We then focus our attention on the well-defined layers of large nocturnal migrants that form in the early evening, usually at heights of 200–500 m above ground. We present evidence from both radar and trap data that these nocturnal layers are composed mainly of noctuid moths, with species such as Noctua pronuba, Autographa gamma, Agrotis exclamationis, A. segetum, Xestia c-nigrum and Phlogophora meticulosa predominating.

The drive towards a more sustainable and integrated approach to pest management has engendered a renewed interest in conservation biological control, the role of natural enemy communities and their interactions with prey. Monoclonal antibodies have provided significant advances in enhancing our knowledge of trophic interactions and can be employed to help quantify predation on target species. The tetragnathid spider Pachygnatha degeeri Sundevall was collected from fields of winter wheat in the UK and assayed by ELISA for aphid proteins. It was demonstrated that this spider did not simply consume greater quantities of aphids because it was bigger. In addition, P. degeeri contained significantly greater concentrations of aphid in their guts than other spiders, showing that aphids comprised a greater proportion of their diet. Although P. degeeri constituted only 6% of the spider population numerically, females and males respectively contained 16% and 37% of total aphid proteins within all spiders screened, significantly more than their density would predict. These spiders also preyed upon aphids at a disproportionately high rate in June, during the aphid establishment phase, theoretically the best time for limiting growth in the aphid population. Although less abundant than other generalist predators, the capability of these hunting spiders to consume large numbers of aphids highlights them as a more significant component of the predator complex than had previously been realized. Limitation of aphid numbers early in the year by generalist predators provides more time for the specialist aphid predators and parasitoids to move in.

Under certain conditions, Callosobruchus maculatus (F.) produces males and females which are distinct from the normal ones. These are called here the “ active ” form, and in southern Nigeria they occur most commonly during the months March to June. The active form has a longer pre-adult stage than has the normal form and it flies readily, unlike the normal form. There is some evidence which indicates that a genetic factor is involved in the production of the active form but no clear indication as to what external factors are involved. The normal female has mature eggs in its calyces within a day of emergence, and will lay about 60 eggs. The active female was found to have immature ovaries on emergence and these did not develop to any great extent in the conditions employed. About three-quarters of the active females never produce any eggs, and the rest produce an average of seven. This difference in egg-production probably makes food reserves available which are used to prolong the life of the active female. The eggs laid by active females are rarely fertile, and when adults do emerge they are apparently normal males and females.

The study identified insecticidal effects from the cinnamon and clove essential oils in Tenebrio molitor L. (Coleoptera: Tenebrionidae). The lethal concentrations (LC50 and LC90), lethal time, and repellent effect on larvae, pupae, and adults of T. molitor after exposure to six concentrations of each essential oil and toxic compounds were evaluated. The chemical composition of the cinnamon oil was also determined and primary compounds were eugenol (10.19%), trans-3-caren-2-ol (9.92%), benzyl benzoate (9.68%), caryophyllene (9.05%), eugenyl acetate (7.47%), α-phellandrene (7.18%), and α-pinene (6.92%). In clove essential oil, the primary compounds were eugenol (26.64%), caryophyllene (23.73%), caryophyllene oxide (17.74%), 2-propenoic acid (11.84%), α-humulene (10.48%), γ-cadinene (4.85%), and humulene oxide (4.69%). Cinnamon and clove essential oils were toxic to T. molitor. In toxic chemical compounds, eugenol have stronger contact toxicity in larvae, pupae, and adult than caryophyllene oxide, followed by α-pinene, α-phellandrene, and α-humulene. In general, the two essential oils were toxic and repellent to adult T. molitor. Cinnamon and clove essential oils and their compounds caused higher mortality and repellency on T. molitor and, therefore, have the potential for integrated management programs of this insect.

It is well known that amongst the sibling species of the Anopheles gambiae complex, A. arabiensis Patton predominates over A. gambiae sensu stricto Giles in hotter, drier parts of Africa. Here it was investigated whether A. arabiensis is better adapted to higher temperatures than A. gambiae s.s. at the microclimatic level. Bioassays were used to assess behavioural avoidance activity of adult mosquitoes in the presence of increasing temperature. Female mosquitoes were introduced into a holding tube from which they could escape into a cage through a one-way funnel. From a starting temperature of 28°C they were exposed to a 2°C rise in temperature every 30 min until all mosquitoes had escaped or been knocked down. As temperature increased, A. arabiensis left the holding tube at higher temperatures than A. gambiae s.s. (A. arabiensis mean activation temperature = 35.7°C, 95% CIs = 35.4–36.1°C; A. gambiae s.s. = 33.0°C, 32.5–33.5°C). To determine the relative ability of both species to survive at extremely high temperatures, batches of insects were exposed to 40°C for different periods. It took considerably longer to kill 50% of A. arabiensis at 40°C than it did A. gambiae s.s. (112 min vs. 67 min). These data show that adult A. arabiensis are better adapted to hotter conditions than A. gambiae s.s., a characteristic that is reflected in their spatial and temporal distribution in Africa.

It has previously been shown that the sexual maturation of males of Scliistocerca grcgaria (Forsk.) is accelerated by crowding with other individuals of similar or greater age, and that the maturation of males kept in single pairs with older mature males is accelerated as compared with that of isolated males or males kept in single pairs with other young males or females of their own age. The effects of these groupings on the levels of feeding and excretion are investigated in the present work.

Crowded males ate and excreted more than isolated ones during the first ten days of adult life. Five males in a 9-litre cage are sufficient to induce almost the full effect of crowding, and marked effects are shown when only two males are present in such a cage.

After the second or third week, the level of feeding declines. This occurs earlier in early-maturing individuals, so that for a short period the crowded males eat little more or even less than the isolated ones. When the isolated males in their turn become mature their feeding again falls slightly below that of the crowded ones. When all males are isolated, there is a significant tendency for those males which eat least from the beginning of adult life and which increase their weight least to become mature earliest.

The proportion of the food utilised was not affected by density. It was higher during the early period of maximum consumption than it was after the level of feeding declined.

A range of techniques was used to quantify the nocturnal flight behaviour of Helicoverpa armigera (Hübner) in pigeon pea (Cajanus cajan) crops near Hyderabad, in central India. These included visual observations in the field, the use of field cages and a vehicle-mounted net, optical and video imaging in the infra-red, and radar. Moth emergence from the soil was observed to start at dusk and recruitment continued steadily throughout the first half of the night. Little activity was observed in moths on the night of emergence, except for weak flying or crawling to daytime refuges. Flight activity of one-day old moths started about 20 min after sunset, peaked 15 min later and within about an hour of sunset had declined to a low level which persisted for the rest of the night. Flight of reproductively mature moths was most frequent about 1 h after sunset and at this time mainly comprised females searching for oviposition sites and nectar sources. By about 2 h after sunset, flight had decreased markedly, but there was a slight increase in activity in the second half of the night caused by males undertaking mate-finding flights. Under the conditions studied, the majority of H. armigera dispersed below 10 m, and there were no mass ascents to higher altitudes like those observed at outbreak sites of the African armyworm, Spodoptera exempta (Walker) (Lepidoptera: Noctuidae). The contrasting migratory strategies of H. armigera and S. exempta are briefly discussed.

The impact of predation by the generalist carabid beetle Pterostichus melanarius (Illiger) on populations of the field slug Deroceras reticulatum (Müller), and the effects of prey size on the predator–prey interaction, were measured under semi-field conditions. It was hypothesized that environmental heterogeneity would lead to very different patterns of comparative mortality than might be deduced from size choice experiments conducted in the laboratory. Results from outdoor mini-plots, emulating conditions in a field of wheat, demonstrated that P. melanarius significantly reduced numbers of slugs from all size classes, with no apparent preferences. This was in marked contrast to results from earlier laboratory studies, where this beetle fed preferentially on the smallest slugs. The slugs in the mini-plots ranged in size from 2–100 mg and the numbers in the mini-plot reflected the size frequency distribution in the field. Beetles in mini-plots containing high densities of slugs increased significantly in weight, in contrast to beetles in mini-plots with low slug density or no added slugs, which did not. Enzyme-linked immunosorbent assays (ELISA), using anti-slug monoclonal antibodies, showed that where there was a higher density of slugs there was more slug protein in the guts of the beetles. It was concluded that environmental heterogeneity probably provided a greater number and diversity of refugia for smaller than for larger slugs, counteracting laboratory-measured size preferences measured in arenas without refugia. These results have implications for a range of ecological studies involving inter- and intra-specific prey size choice, and emphasize the dangers of extrapolating from the laboratory to the field.

The distribution and seasonal activity of Onthophagus granulatus Boh. was studied at two sites in eastern Australia. It is a univoltine species, with peaks of activity in spring and early summer. Breeding cycles and periods of stress were demonstrated by the proportions of newly emerged, nulliparous and parous beetles and those resorbing oocytes. The optimum temperature for brood production was 25°C. The threshold of development was 11·3°C, and 495 day-degrees C were required for development from egg to adult. Dung quality and drought were important factors affecting survival and brood production in the field. The distribution of the species in south-eastern Australia is limited by summer rainfall and temperature.

Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is a pest species complex that causes widespread damage to cassava, a staple food crop for millions of households in East Africa. Species in the complex cause direct feeding damage to cassava and are the vectors of multiple plant viruses. Whilst significant work has gone into developing virus-resistant cassava cultivars, there has been little research effort aimed at understanding the ecology of these insect vectors. Here we assess critically the knowledge base relating to factors that may lead to high population densities of sub-Saharan African (SSA) B. tabaci species in cassava production landscapes of East Africa. We focus first on empirical studies that have examined biotic or abiotic factors that may lead to high populations. We then identify knowledge gaps that need to be filled to deliver sustainable management solutions. We found that whilst many hypotheses have been put forward to explain the increases in abundance witnessed since the early 1990s, there are little published data and these tend to have been collected in a piecemeal manner. The most critical knowledge gaps identified were: (i) understanding how cassava cultivars and alternative host plants impact population dynamics and natural enemies; (ii) the impact of natural enemies in terms of reducing the frequency of outbreaks and (iii) the use and management of insecticides to delay the development of resistance. In addition, there are several fundamental methodologies that need to be developed and deployed in East Africa to address some of the more challenging knowledge gaps.

Glossina morsitans morsitans Westw. and G. pallidipes Aust. flying to and from a stationary ox were captured by a wall of electrocuting netting at distances ranging from 45 m upwind of the ox to 120 m downwind. The pattern of catches at each distance suggested that most flies not recently fed were attracted to the ox from downwind, from distances up to about 90 m. Most flies leaving the ox flew downwind. This was most marked for flies that had fed on the ox, some of which travelled 120 m within about 30 min of engorging.

The study of intraspecific variation with respect to host plant utilization in polyphagous insects is crucial for understanding evolutionary patterns of insect-plant interactions. Aphis gossypii (Glover) is a cosmopolitan and extremely polyphagous aphid species. If host plant species or families constitute selective regimes to these aphids, genetic differentiation and host associated adaptation may occur. In this study, we describe the genetic structure of A. gossypii collected in six localities in Tunisia on different vegetable crops, on citrus trees and on Hibiscus. The aim was to determine if the aphid populations are structured in relation to the host plants and if such differentiation is consistent among localities. The genetic variability of A. gossypii samples was examined at eight microsatellite loci. We identified only 11 multilocus genotypes among 559 individuals. Significant deviations from Hardy-Weinberg equilibrium, linkage disequilibria and absence of recombinant genotypes, confirmed that A. gossypii reproduces by continuous apomictic parthenogenesis. Genetic differentiation between localities was not significant, whereas a strong differentiation was observed between host plant families (0.175<FST<0.691). The great majority of aphids exhibited one of three predominant multilocus genotypes that were repeatedly and respectively associated to the three plant families, Cucurbitaceae, Solanaceae and Rutaceae, demonstrating host specialization in A. gossypii. These specialized genotypes were simultaneously found with other clones on Hibiscus, suggesting that this perennial host could act as a refuge plant between two vegetable crop seasons.

A pilot field study, involving periodic augmentative release of predatory larvae of a dragonfly, Crocothemis servilia (Drury), to suppress a mosquito, Aedes aegypti (Linnaeus), was conducted during the rainy season in Yangon (Rangoon). More than 90% of pre-adult A. aegypti occurred in domestic water-storage containers. Evaluations of larval and adult numbers of A. aegypti were made half-monthly three times before, and seven times after, treatment began. Four laboratory-reared, three-week-old C. servilia larvae were placed in each major source of A. aegypti larvae immediately after the third evaluation and then monthly for three successive months. Such treatment reduced the larval population of A. aegypti to a very low level in two to three weeks and suppressed it progressively until the trial ended; the adult population was greatly reduced after about six weeks and was progressively diminished thereafter until the trial ended. The trial's success was ascribed to: the virtual confinement of pre-adult stages of the target mosquito to containers accessible to control operators; the behaviour, growth rate, survival and ready availability of the chosen species of dragonfly; and the awareness and enthusiastic participation of local householders.

In the ichneumonid wasp Diadromus pulchellus (Wesmael), diploid males may regularly be produced in laboratory populations by inbreeding. They are viable, produce diploid sperm and are equally capable of multiple inseminations as are haploid males. Their spermatozoa are also able to penetrate the oocyte. Progeny sired by diploid males are essentially haploid sons with only a few daughters. The sons are normal haploid individuals, produced in a frequency significantly higher than in crosses between females and haploid males. The daughters are normal diploid females probably resulting from the fertilization of an oocyte by an exceptional haploid sperm rarely produced by diploid males. Triploid individuals were not observed and their absence was correlated with the high mortality observed during the first developmental stages. The death of these individuals is discussed in the light of the phenomenon of superparasitism to explain the increase in the frequency of sons produced in crosses with diploid males. Despite their viability, their ability to produce sperm and their normal potential insemination, diploid males of Diadromus pulchellus are therefore almost sterile.

The mosquito sampling efficiency of CDC (Centers for Disease Control) miniature light traps hung adjacent to mosquito nets, was compared with that of both indoor and outdoor human-bait collections in ten villages in the Wosera area of Papua New Guinea. The most frequently collected anopheline in the matched indoor and light trap samples was Anopheles koliensis Owen, followed by A. punctulatusDönitz, A. karwari (James), A. farauti Laveran (sensu lato), A. longirostris Brug and A. bancroftii Giles. All species were much less frequent in the light traps than in landing catches. The hypothesis that the numbers of mosquitoes in light traps are proportional to human landing catches was examined using regression models that allowed for sampling error in both entomological measurements. Light traps under-sampled A. punctulatus and A. farautis.l. at high densities. The models indicated that the ratio of light trap to landing catch females of A. koliensis and A. karwari increased with increasing mosquito density. Light trap catches of A. longirostris were proportional to indoor landing rates but when outdoor landing rates were high this species was under-sampled by light traps. Numbers of A. bancroftii in light traps were found to be proportional to those in outdoor landing catches, but were negatively related to those attempting to bite indoors. Circumsporozoite positivity rates for both Plasmodium falciparum Welch and P. vivax (Grassi & Feletti) in A. punctulatus and A. farauti s.l. were significantly higher in light trap collections than in either indoor or outdoor landing catches, suggesting that light traps may selectively sample older mosquitoes of these species.

The effects of DDT on the behaviour and mortality of Anopheles gambiae Giles, A. funestus Giles, Mansonia uniformis (Theo.) and Culex pipiens fatigans Wied., entering experimental huts, have been studied with the assistance of gas-chromatographic techniques.

Sixty to 70% of A. gambiae and 70–80% of M. uniformis were deterred from entering verandah-trap huts treated indoors with a nominal dosage of 200 μg/cm2 of DDT active ingredient. Gas chromatographic techniques indicate that the chemical basis of the deterrency was a steadily diminishing outflow of DDT from the hut, either as a dust or vapour, and the build-up of deposit on the untreated overhanging eaves to 0·02 to 0·27 μg/cm2 seven months after treatment. A. funestus was less deterred than A. gambiae and M. uniformis, but the behaviour of C. p. fatigans was almost unaffected by the DDT deposit.

Overall mortalities were highest in A. funestus and M. uniformis, lower in A. gambiae and extremely low in C. p. fatigans.

There was a marked irritant effect of the DDT deposit on recently blood-fed A. gambiae, some 50–70% being driven out of the treated huts. This behaviour occurred to a lesser degree in A. funestus but was absent in M. uniformis and C. p. fatigans. The chemical basis of the irritant effect was indicated to the extent that surviving mosquitoes, that left the treated hut, showed 1·5 ng/insect of DDT. Mosquitoes that died, whether indoors or after leaving the hut, picked up amounts ranging from 7 to 20 ng/insect.

The role of silicon (Si) in alleviating the effects of biotic and abiotic stresses, including defence against insect herbivores, in plants is widely reported. Si defence against insect herbivores is overwhelmingly studied in grasses (especially the cereals), many of which are hyper-accumulators of Si. Despite being neglected, legumes such as soybean (Glycine max) have the capacity to control Si accumulation and benefit from increased Si supply. We tested how Si supplementation via potassium, sodium or calcium silicate affected a soybean pest, the native budworm Helicoverpa punctigera Wallengren (Lepidoptera: Noctuidae). Herbivory reduced leaf biomass similarly in Si-supplemented (+Si) and non-supplemented (–Si) plants (c. 29 and 23%, respectively) relative to herbivore-free plants. Both Si supplementation and herbivory increased leaf Si concentrations. In relative terms, herbivores induced Si uptake by c. 19% in both +Si and –Si plants. All Si treatments reduced H. punctigera relative growth rates (RGR) to a similar extent for potassium (−41%), sodium (−49%) and calcium (−48%) silicate. Moreover, there was a strong negative correlation between Si accumulation in leaves and herbivore RGR. To our knowledge, this is only the second report of Si-based herbivore defence in soybean; the rapid increase in leaf Si following herbivory being indicative of an induced defence. Taken together with the other benefits of Si supplementation of legumes, Si could prove an effective herbivore defence in legumes as well as grasses.

Deforestation has been linked to a rise in malaria prevalence. In this paper, we studied longitudinally 20 spots, including forested and deforested portions of a temporary river in a malarigenous frontier zone. Larval habitat parameters influencing distribution of Anopheles darlingi (Diptera: Culicidae) larvae were studied. We observed that larvae were clustered in forested-deforested transitions. For the first time in the literature, it was verified that parameters determining larval distribution varied from deforested to forested areas. The proximity to human dwellings was also a significant factor determining distribution, but larvae was most importantly associated with a previously undescribed parameter, the presence of small obstructions to river flow, such as tree trunks within the river channel, which caused pooling of water during the dry season (‘microdams’). In deforested areas, the most important factor determining distribution of larvae was shade (reduced luminance). Larvae were absent in the entire studied area during the wet season and present in most sites during the dry season. During the wet-dry transition, larvae were found sooner in areas with microdams, than in other areas, suggesting that flow obstruction prolongs the breeding season of An. darlingi. Adult mosquito densities and malaria incidence were higher during the dry season. Our data correlate well with the published literature, including the distribution of malaria cases near the forest fringes, and has permitted the creation of a model of An. darlingi breeding, where preference for sites with reduced luminance, human presence and microdams would interact to determine larval distribution.