The study of life history traits in tropical insects is still in its infancy. We are just beginning to appreciate that tropical insects do not all develop and reproduce continuously throughout the year. Developmental and reproductive events may be as highly seasonal in tropical species as they are in insects from the temperate zone. Yet, little is known about the evolutionary forces that shape the life history traits of tropical species. What are the developmental options and what dictates which option is expressed? What are the ultimate factors determining whether a species will diapause or develop without interruption? What other life history traits are linked to the decision to diapause or not to diapause? What environmental cues are utilized by tropical insects to regulate seasonal cycles, and how are these cues translated into meaningful hormonal signals that direct the insect's development fate?

In order to evaluate the migratory potential of the brown planthopper, Nilaparvata lugens, under as near to normal environmental conditions as possible, adult macropterous insects were captured from the field whilst in the process of flight initiation at the times of their natural take-off peaks. The insects were then flight-mounted and flown in the field. Average flight durations following the dusk take-off were 4 hr 55 min for males and 6 hr 17 min for females. However, many insects flew throughout the night and there was a high frequency of flight cessation at dawn. Following a dawn take-off both sexes flew for much shorter periods, an average of 2 hr 00 min for males and 2 hr 04 min for females. Female insects were reluctant to initiate a second major flight. The role of mating and ovary development in female flight willingness is discussed.

Recent surveys have shown that ant-Homoptera associations are not limited to cocoa trees only but a large number of other plant species serve as hosts for such associations. It has been observed that some ant species may tend more than one Homopteran species on a number of different host plants. Seasonal abundance of the homopterans and their tending ants was studied on cocoa, mango and pigeon pea.

The populations of the ants tend to synchronize with the populations of the Homopterans which they tend during the season.

The relative activity of three concentrations of Spodoptera littoralis nuclear polyhedrosis virus (SLNPV) against Ceratitis capitata were determined by (a) submerging two egg age groups, freshly laid eggs (0–2.5 hr) and more older ones (0–24 hr) in viral concentrations, and (b) feeding newly hatched larvae on viral contaminated media. Pupations that resulted from all viral treatments were decreased with increase of virus dose. Hatchability showed the same relation, but hatchability of treated old eggs were not significantly influenced by increases in viral concentration. Adult emergence was significantly reduced due to viral treatments to eggs, however, it was increased in the case of feeding the larvae on contaminated diet. The most hypothetical probability of this deleterious effect may be attributed to an activation of an indigenous virus already present in C. capitata. More research is required to understand the basis for the deleterious effect of SLNPV on the fruit fly.

Egg distribution on cowpea seeds and the influence of seed population on extent of oviposition by Callosobruchus maculatus (F.) were investigated in this study. Majority of the eggs were laid on the cheek of the cowpea seeds. The number of eggs laid by females increased with increase in seed population. The results are discussed in relation to observations on oviposition behaviour of C. maculatus reported by earlier workers.

Electrophoretic variation was determined at eight enzyme loci in Anopheles arabiensis from four villages in Mwea Irrigation Scheme, Kenya. Seven loci had polymorphic alíeles of which at least two were common. Pooled allele frequencies at the Pgm, β-Had and Odh loci were in Hardy-Weinberg equilibrium, while those at the Ao, Idh, Adh, Est-1 and 6-Pgd loci showed significant deviations. The frequency of heterozygotes at the Adh, Est-1 and 6-Pgd loci was less than expected, while at the Ao locus, there was an excess. A 2 × 4 contingency χ2-test for each of the loci not in Hardy-Weinberg equilibrium indicated an association between the respective gene frequencies and the villages. The suggested explanation for these observations is that each village constitutes a distinct population, and that the pooled data introduced the Wahlund effect. Allele frequencies at individual loci per village population are most likely at Hardy-Weinberg equilibrium. Larger samples per village need to be examined to facilitate a goodness of fit χ2-test between observed and expected frequencies.

Four types of trap, yellow water, yellow sticky board, bottle with 20% protein hydrolysate, and funnel with 10% casein hydrolysate, were field-tested to control Liriomyza huidobrensis (Blanchard) in the coastal region of Peru. The yellow sticky boards were the most effective in trap capture with a mean of 1193.92 L. huidobrensis per week. The male:female capture ratio was 16:1.

Five parasitoid species, Halticoptera palellana, Chrysocharis phytomyzae, Chrysocharis sp., Diglyphus sp. and Opius sp., were also trapped. A significant negative correlation (r = −0.607 at P < 0.05) was observed for female leafminer capture vs temperature. Wind velocity was positively correlated with parasitoid capture (r = 0.509 at P < 0.05). The population of adult L. huidobrensis was significantly lower (P < 0.05) in plots with yellow sticky boards. Yields in plots with yellow sticky boards and those treated with insecticides were similar and significantly higher (36%) than check plots.

The band-legged ground cricket group comprises a pair of very closely related species; Dianemobius fascipes occurs widely over tropical and subtropical regions of Southeast Asia, while D. nigrofasciatus is restricted to temperate regions. A similar situation is found in the lawn ground cricket group; the tropical/subtropical species D. taprobanensis is replaced by D. mikado in temperate regions. In both southern species, tropical strains were almost homodynamic, but they produced a few delayed eggs independently of photoperiod and a variable proportion of macropters in response to photoperiod; subtropical strains showed clearer responses. Both northern species controlled egg diapause, nymphal development and wing form by various photoperiodic responses. The two species groups showed parallel geographical profiles of size variation, and the adults and eggs were smaller in the southern than in the northern species. In the absence of strong climatic selection for larger growth rate, size increase in tropical regions would be counteracted by predation pressure. The optimal adult size thus seems to be smaller in tropical than in temperate regions, being determined by the geographically variable balance between counteracting selecting forces.

Field studies on aphid species on cabbage were conducted from 1982 to 1984. Brevicoryne brassicae L. commonly occurred on cabbage in Jos Plateau. No aphids were observed on plants transplanted in November 1982 within the first 2 weeks while those transplanted in January 1984 and February 1983 and 1984 usually had a weekly mean of more than five aphids/plant which necessitated application of aphid control treatment. High uncontrolled infestations of B. brassicae on plants aged 2–3 weeks after transplanting usually resulted in stunted growth, plant death and low yields. Decis at 7.5, 12.5 and 17.5 g a.i./ha, dichlorvos at 500, 750 and 1000 g a.i./ha, carbofuran 3 G at 1000 g a.i./ha, carbaryl 85 at 1000 g a.i./ha, and hand-washing of plants with water were used in the study. Decis, dichlorvos and carbofuran applied at 12.5, 750 and 1000 g a.i./ha respectively, were more effective in B. brassicae control. The overall cumulative mean number of B. brassicae/plant on untreated plants were 1300, 1087, 1672 and 565 for crops one to four respectively. For each crop the mean aphid number on untreated plants was significantly higher (P < 0.05) than those on treated plants. For each of the 1984 crops the yields (kg/head) from treated and untreated plants, did not differ significantly (P > 0.05), but for each of the 1982 and 1983 crops, the yields from treated and untreated plants differed significantly (P < 0.05). Plants receiving the washing technique of aphid control out-yielded untreated plants while carbofuran treated plants generally out-yielded plants receiving all other treatments.

Samples of ground beetles (Carabidae) were collected throughout the year-long 1985 Joint Indonesian–Royal Entomological Society expedition, Project Wallace, in an area of rain forest in N. Sulawesi. The beetles were collected by a range of collecting techniques including insecticide fogging, malaise, flight interception, pitfall and light trapping as well as hand collecting. The state of ovary maturation was determined by dissecting the females. A high number of species of Carabidae show a distinct seasonal reproductive rhythm in the form of gonad dormancy, avoiding reproduction in the slightly cooler months in the middle of the year. In contrast, most species of tiger beetles (subfamily Cicindelinae) are reproductively active at this time of year. The study area appears to have an unusually variable monthly rainfall for this region, and we suggest that the seasonality in the ground and tiger beetles is a response to the strict annual rainfall patterns of the coastal areas 10–20 km to the north and south.

Insect growth regulating properties of petroleum ether extracts of 10 indigenous plants were tested against Culex pipiens fatigans (Wied) and Musca domestica nebulo (Fabr) by continuous exposure and topical application methods. Out of the 10 plants, Acorus calamus and Azadirachta indica demonstrated insect growth regulatory (IGR) activity against C. p. fatigans and also against M. d. nebulo. There was IGR activity, but this was observed only when these extracts were used in higher concentration.

The field experiments were conducted during the summer of 1985 to determine the degree of winter wheat resistance to the grain aphid Sitobion avenae. Asta, Grana, and Saga cultivars were generally more resistant than Dana, Liwilla, and Emika. The resistance mechanism involved both antixenosis and antibiosis. Grana was least preferred during aphid migration. Asta, Saga, and, to a lesser extent, Grana had an antibiotic effect on growth and development of the apterous aphids (longer prereproductive period, lower fecundity and lower values of the intrinsic rate of increase, rm, during the first days of reproduction). Moreover, var. Asta showed a “secondary antixenosis” during colonization of ears due to the presence of awns.

Six transformations viz., , log[log (x + 2)] and log[log (x + k )] were tested for their efficiency in stabilizing variance of Coccus viridis (Green) population counts which followed negative binomial distribution. Only log[log(x + 2)] transformation was found effective in stabilizing variance. This is a new transformation proposed by the authors.

Two antifeedants, isopongaflavone and tephrosin have been isolated from Tephrosia elata. Tephrosin displayed high activity against Spodoptera exempta, while isopongaflavone was shown to be very active against Maruca testulalis and Eldana saccharina. Rotenone was found to be active as an antifeedant against S. exempta, E. saccharina and M. testulalis. Insects in the orders Coleoptera, Hymenoptera, Lepidoptera and Diptera, all associated with T. elata seed pods, were identified.

The effect of 10, 20, 30, 40, and 50 adult Sitophilus zeamais on the quality of 1 kg lots of white maize maintained at 25−30°C and 65−85% r.h. was observed. Per cent moisture, oil, Free Fatty Acid (FFA) content and germination were determined at 2-week intervals for 10 weeks.

Moisture content of infested maize ranged from 11.51 to 12.92%. There was a significant correlation between moisture content and degree of infestation (r = 0.88; P < 0.05; Y = 11.908 + 0.006 x). The range of oil content of infested maize was 4.83−5.75%. There was a significant correlation between oil content and degree of infestation (r = −0.097; P < 0.05; Y = 5.08 −0.0076 x). The free fatty acid (FFA) of infested maize was 5.82−6.86%. The heterogeneity at various infestation levels was significant (F = 81.38; d.f. = 5; P < 0.001). There was an increase in FFA, with increasing infestations, although the correlation was not significant.

The germination of maize, 10 days after planting, at various infestation levels was 43.0−97.5%. There was a decrease in germination, as level of infestation increased. The heterogeneity in germination at various infestation levels was significant (F = 19.21; d.f. = 5; P < 0.001). Possible reasons for the results obtained, are presented.

The dry and largely deciduous forests in Santa Rosa National Park in northwestern lowland Guanacaste Province, Costa Rica, Central America, have a moth fauna of about 2800 species. These moths pass the six month rain-free dry season, and some other portions of the year, by: (a) remaining dormant in the egg stage (1 species only), (b) remaining dormant in the pupal or prepupal stage (many species), (c) undergoing larval development (a few species of particular life forms) (d) remaining in the Park as a potentially active but non-reproductive adult (many species), and (e) migrating out of the Park after one to two generations and then returning at the beginning of the following rainy season (a few species of particular life forms). The migrating moths constitute a strong link between the dry forest and the rainforests to the east of the dry forest. The seasonal patterns of dormancy of immatures, reproductively dormant adults, and migration are not well correlated with the simple presence or absence of foliage on host plants, or with climate changes (except that the temperature drop that occurs at the beginning of the rainy season appears to be a widely used cue for pupal eclosion). The pattern of habitat use by leaf-eating caterpillars is probably determined more by the seasonal abundance of carnivores (parasitoids and predators) than by the mere presence of leaves; this process is very strongly evident in the failure of many moths to have more than one generation per year, even when their host plants are leafy throughout the six month rainy season or are even evergreen.

The southwestern corn borer, Diatraea grandiosella, has expanded its range during this century so that it is now distributed between about 18 and 38°N latitude in Mexico and the United States. The species survives from year to year by entering a facultative larval diapause, and over most of its range it is bivoltine or trivoltine. Fully grown pre-diapausing larvae prepare an overwintering cell in the stalk crown of their host plant, typically maize, and then ecdyse from a spotted to a pigment-free morph at the onset of diapause. Southwestern corn borers originally obtained from southcentral Mexico (19°N latitude) and the United States (33–38°N latitude) were reared on an artificial diet under standardized conditions to compare several of their life history traits. Information is presented about voltinism, photoperiodic responses, growth and reproduction, larval behaviour and ecdyses, and the diapause-associated protein in an attempt to evaluate characteristics that have enabled the species to disperse from a tropical to a temperate region.

The relative pathogenicity and toxicity of nuclear polyhedrosis virus of the cotton leafworm, Spodoptera litioralis (Boisd.) (SLNPV) and three pesticides, namely DC–702, DC–703 and DC–800, were investigated against the second- and fourth-instar larvae of S. littoralis. Results revealed that the second instar was more susceptible to the action of all treatments than the fourth instar. Among the tested insecticides, DC–703 was most toxic for either instars, followed by DC–800 and DC–702 for the second instar larvae. Fourth-instar larvae were more susceptible to DC–702 and DC–800, respectively. Combination of virus and DC–702 gave increased larval mortality when compared with the effects of either alone. On the other hand, antagonistic effect occurred when DC–703 was combined with NPV. This may be due to the high percentage of diflubenzuron (4.8%) as one of the components of DC–703, while DC-702 contains only 2.4% diflubenzuron. Synergistic interactions of mixtures containing low concentrations of SLNPV and DC–702 or DC–800 may be effective against S. littoralis and more safe for other biotic control agents.

Literature on the distribution, biology, seasonal population fluctuations, economic importance, acaricidal susceptibility and measures for the control of the cattle ticks Boophilus microplus Canst., Amblyomma cajennense Fab., A. variegatum. Fab. in the Caribbean has been critically reviewed. The ticks, which inflict about $62 million annual loss on the region's livestock industry, are still susceptible to acaricides, despite a few populations of B. microplus showing 31- to 227-fold resistance to lindane and 15- to 67-fold resistance to carbaryl, chlorfenvinphos, dimethoate and crotoxyphos.

The screwworm, Cochliomyia hominivorax Coq. is widespread, except in Puerto Rico and Curacao, from where it has been eradicated. The annual cost of surveillance against the fly and treatment of cattle for myiasis is estimated to be about $59 million. Its eradication from the entire Caribbean region by insect sterile method is advocated.