Brugia pahangi microfilariae obtained from peritoneal washings of jirds (Meriones unguiculatus) were incubated with midgut tissue of Culex quinquefasciatus and Aedes aegypti (susceptible stock), in the presence or absence of blood and also in thoracic tissue and salivary glands in various media. Exsheathment took place in the presence of midgut tissue with or without blood and in thoracic tissue, but not in the presence of salivary glands.

Percentage exsheathment was variable and not reproducible for each type of tissue. Exsheathment also occurred in the presence of mosquito cells in suspension and in monolayers. In the latter, percentage exsheathment in some cases was higher than that observed in vivo in the midgut of C. quinquefasciatus, which is refractory to B. pahangi microfilariae.

The horseflies in a patch of gallery-forest in a savannah of French Guiana were collected by 1°) for 24 hr with a Malaise trap, and 2° for 2 hr at dawn and at dusk, with a Malaise trap baited with carbon dioxide. The crepuscular horseflies, Cryptotylus unicolor, Chlorotabanus mexicanus and Chlorotabanus inanis, were more abundant in the baited trap (average: 55% of the flies collected) than in the unbaited trap (3%). Seasonal changes in relative abundance of the crepuscular species were evident in the baited trap only. The baited trap caught more flies and more species (averages: 315 flies and 7.5 species per 2hr catch) than the unbaited trap (averages 64 flies and 5.1 species per 24 hr catch). However, the overall number of species collected in each trap during the study did not differ greatly (16 species for 126 catches of 24 hr for the unbaited trap vs. 14 species for 29 catches of 2 hr for the baited trap).

Haemocoelic injections of live Escherichia coli and oral administration of three tetracycline compounds, namely Reverin, Maxitet and Terramycin to female Glossina morsilans morsitans prior to their first larviposition, caused a decrease in fecundity, but had no effect on longevity. Trypanosoma brucei brucei and T. congolense administered by haemocoelic injections, however, caused no change in fecundity or longevity, but tsetse infected with T. b. brucei and T. congolense in their mouthparts had decreased fecundity and longevity as compared to controls.

The main effects of gall midges in tropical agriculture are as primary pests of cultivated plants; as predators on pests, especially mealybugs, scale insects and mites; as potential biocontrol agents of weeds and as pollinators of cocoa. Published information is briefly reviewed under these main headings, with particular emphasis on the sorghum midge, Contarinia sorghicola (Coquillett), on the Asian and African rice gall midges, Orseolia oryzae (Wood-Mason) and O. oryzivora Harris & Gagné and on cecidomyiid predators on mealybugs and scale insects.

The study showed how trails were established with and without any food source. The two stimulants for strong trail-laying by the termites were found to be: (1) a virgin (trail-less) surface, and (2) a discovered food source. Whenever a food source was discovered, the returning workers (from the food source to the nest) increased strong trail-laying (STL) activity more than the outgoing termites.

The results also confirmed that there was no trail specificity (neither in artificial trail extracts nor in natural trails) between different colonies of Amitermes evuncifer. This means that in trail bioassays, test termites can be taken from any colony (of the same species). A method devised for extracting, preserving as well as carrying out tests with extracted natural trail was discussed.

Trail activity was measured in terms of “trail unit” (TU). The trail activity of a single worker sternal gland was found to be 15,000 TU. This is the highest activity ever found in a worker of any termite species. This study has confirmed chemical communication in Amitermes evuncifer.

Steam distillates of seven Nigerian plants, Lippia adoensis Hoschst, Azadirachta indica A. Juss, Monodora tenuifolia Benth, Piper guineense Schum & Thonn, Petiveria alliacea L., Citrus sinensis L. (variety Nigerian green orange), and Cymbopogon citratus L. were tested for acute toxicity on four major insect pests. The pests were larvae of Acrae eponina Cramer, adult cotton stainer Dysdercus superstitiosus (F.), the cowpea flea beetle, Ootheca mutabilis Sahlberg and the pod sucking bug Riptortus dentipes F. Essential oils of L. adoensis, M. tenuifolia and P. guineense were toxic to the insects. O. mutabilis was the most susceptible with LD50 of 0.15, 0.32 and 0.52 respectively for M. tenuifolia, L. adoensis and P. guineense, while R. dentipes was the least susceptible. There was cessation of feeding in A. eponina treated with essential oil of C. sinensis and P. alliacea.

Tests on the quantitative adsorption of polyhedra of nuclear polyhedrosis virus of Heliothis armigera to black and red soil showed an increase in the adsorption of polyhedra with an increase in the amount of soil. The increase was higher in the red soil than black soil, but the number of polyhedra adsorbed per unit weight of soil decreased as the amount of soil increased; the rate of decrease being faster in black soil than in red soil. The adsorption of polyhedra of nuclear polyhedrosis virus of Heliothis armigera is discussed based on certain physico-chemical properties of both red and black soils.

With perhaps a thousand species present in the endemic fauna, the Hawaiian Drosophilidae represents one of the most striking examples of explosive adaptive radiation known in the animal kingdom. However, there is mounting evidence that it is shifts within the sexual environment that are more important in the speciation process. Classical concepts of sexual selection theory are reviewed and some new ideas regarding the role of sexual selection in the origin of secondary sexual characters are presented. It is suggested that there is a range of mating types in both sexes and that differential selection between the two sexes, i.e. selection for males with superior mating ability and for less discriminant females, results in the maintenance of an optimum behavioural phenotype in the population. It is further suggested that the dynamics of the sexual selection process and the effects of pleiotropy play a significant role in levels of genetic variability in a single interbreeding population.

Temperature influences the reproductive capacity of the Saissetia coffeae and its parasitoid. The lowering of temperatures increased the egg production of the scales. The high temperature (30°C) reduced the egg-laying of Metaphycus helvolus and resulted in a greater proportion of male progenies. However, oviposition and sex ratio of Scutellista cyanea were unaffected by high temperature. The high temperature too, accelerated the development of ovarian eggs of both parasitoids.

Biotypes refer to the infraspecific category of insect populations with similar genotypes for biological attributes. They have been encountered mostly in association with cultivation of resistant crop cultivars and in well-studied cases a gene-for-gene relationship between pest virulence and host plant resistance has been documented. To date, biotypes have been reported to occur in 36 crop pest species belonging to 17 arthropod families in six Orders. Almost 50% of these pest species with known biotypes are aphids. Knowledge of occurrence of insect biotypes is crucial to the success of crop improvement programmes aiming to incorporate pest resistance. Biotypes represent evolutionary transients in the process of speciation and develop through natural selection acting upon genetic variations within the pest populations. To slow down the process of biotype selection, crop cultivars with broad genetic bases are needed.

Studies on the peridomestic resting sites of Glossina f. fuscipes were carried out at night and during the day. Flies were caught, marked with fluorescent powders and then released in coffee and banana plantations, Lantana camara thicket and adjoining forest habitat and the potential resting sites subsequently searched.

Leaves, twigs and branches between 0.5 and 1 cm in dia. are the preferred resting sites of G.f. fuscipes. The resting heights ranged from 0 to 3.66 m. Results are discussed in relation to tsetse control in the Busoga sleeping sickness epidemic area.

Oviposition and development of Evania appendigaster and Tetrastichus hagenowii in live P. americana oothecae ranging in age from 0–44 days was investigated. E. appendigaster oviposited in oothecae of all ages but developed only in 0–28 days old oothecae. T. hagenowii oviposited only in oothecae 0–34 days old, but developed only in 0–28 days old oothecae. Oothecae parasitized by E. appendigaster were superparasitized only during the first 4 days after the initial parasitization. A single parasite emerged from each such oothecae, indicating that only one of the two ovipositions was successful. Oothecae superparasitized by T. hagenowii during the first 8 days of the initial parasitization, resulted in ca. 90 parasites from both ovipositions. Oothecae parasitized by each species of parasite were subjected to multiple parasitism by the other species. Oviposition of E. appendigaster in 0–25 days old oothecae, parasitized by T. hagenowii was ineffective as it resulted in the emergence of T. hagenowii only. Reparasitization of 0–36 days old E. appendigaster-parasitized oothecae by T. hagenowii within 0–32 days resulted in the development of T. hagenowii, but reparasitization thereafter was ineffective as only E. appendigaster emerged. Even though T. hagenowii is more efficient than E. appendigaster, in parasitizing and developing in different types of P. americana oothecae, under field conditions the two species of parasites contribute equally towards the natural control of P. americana.

A sizeable population (60.5%) of muga silkworm (Antheraea assama Westwood, Saturniidae: Lepidoptera) enters pupal diapause in its natural environment in the wild state whereas the development is continuous when reared in the plains (0 to 20 m MSL) under human care (in this practice the larvae are mounted on the food plants with suitable leaves and protected from natural enemies and pass the entire larval stage in the out-door and rest of the development, viz. cocooning, pupation, moth emergence, courtship, copulation, oviposition and embryonic development etc. take place in in-door conditions; the ripe worms are collected from the food plants and put in the cocoonage; after cocoon formation the cocoons are placed in cages for moth emergence; if the moths do not couple naturally, mechanical coupling by gentle rubbing of the genital segments of the opposite sexes is resorted; finally the coupled moths are tied on a straw bundle for oviposition). Inbreeding of diapausing population in plain inhibits dormancy but intercross with the non-diapausing population channels a few pupae (3.5%) into diapause. Low temperature (6–10°C) and short photophase (9 to 10 hr) prevailing in winter in the hills (100 to 450 m AMSL) appear to be the threshold level to induce diapause in muga silkworm.

Abdomen homogenates of refractory C. quinquefasciatus and Anopheles stephensi prepared from equal and varying wet weights of abdomen, were shown to inhibit endopeptidase induced in vitro exsheathment of Brugia pahangi microfilariae. This inhibitory effect was removed by heat treatment and centrifugation of the homogenates. Abdomen homogenate from susceptible Aedes aegypti did not inhibit exsheathment. This suggested the presence of some inhibitory factor in the abdomens of the two insusceptible species of C. quinquefasciatus and An. stephensi. There was no evidence of this inhibitory effect in the midgut homogenates of the three mosquito species. Foetal calf serum and bovine serum albumin also inhibited endopeptidase induced exsheathment of B. pahangi microfllariae, suggesting that the protein concentration of the proteinaceous substances also determined the extent of inhibition. In the absence of endopeptidase, incubation in midgut homogenate of the 3 species of mosquito did not initiate exsheathment, suggesting that the conditions present in vitro did not simulate those persisting in the mosquito midgut in vivo.

Growth and reproduction in Heliothis armigera is known to be controlled by temperature, relative humidity and host plants. Photoperiod was also found to be an important extrinsic factor regulating the different biological aspects of H. armigera. The effect of five alternating light and dark cycles on the adult as well as on the immature stages of this pest was studied at 25 ± 2°C.

The results obtained showed that the photoperiod regimes tested on the adult stage has a high significant effect on reproduction and longevity. Also 16 hr photoperiod was the most suitable condition for maximum egg deposition and maximum percentage of egg hatching.

The immature photoperiod regimes had a high significant effect on the larval duration, pupal weight and percentage of emergence of adults, but had no effect on the pupal duration. Combined effect of immature and adult photoperiod regimes affected greatly the fecundity and longevity of the adults.

Insects have evolved a potpourri of mechanisms for manipulating the allelochemicals that fortify their preferred host plants. A concatenation of physiological and biochemical events frequently follows the ingestion of a toxic natural product and can eventuate in a variety of fates for the compound. A particular allelochemical may be absorbed, metabolized, and sequestered, whereas the fates of concomitant natural products may be very different. Some compounds may be directly excreted in the faeces and their concentration will thus mirror that in the plant. In other cases, selective absorption and sequestration combine to biomagnify minor constituents so that the concentration of these sequestered compounds in insect tissues diners drastically from their concentrations in the host plants.

The acridid Romalea guttata is utilized in this paper as a paradigmatic insect which eclectically processes ingested allelochemicals from a wide range of host plants. This generalist herbivore is eminently suitable as a model because it feeds on plants containing a veritable pharmacopoeia of toxic compounds. The proven sequestrative potential of its defensive glands further qualifies R. guttata as an excellent candidate for determining the fates of toxic phytochemicals. An analysis of this insect's processing strategies for the compounds ingested after feeding on catnip (Nepeta cataria) reveals that for R. guttata variety is the spice of herbivorous life. The results of this investigation persuasively demonstrate that each insect species—and the phytochemical mixture that it ingests—must be regarded as a unique evolutionary case that constitutes a distinctively idiosyncratic phenomenon.

Infection of Diacrisia obliqua larva by Apanteles flavipes resulted in a significant decrease in the lipid and protein content of the host. In about 8 days the parasitoid larvae developing in the host not only utilized these components of the host but also depressed food consumption of the host. Consequently, at the time of emergence of the parasitoid larvae, the host tissue consisted of simply carcass. The parasitoid larvae utilized lipids at the rate of 0.9–10.0 μg/mg/day.

Electrophoretic studies of Guatemalan blackflies, Simulium ochraceum, the main vector of Central American onchocerciasis, were performed using isozyme patterns. A total of six larval and adult populations originating from four localities (a non-endemic area, Finca La Ruda, a low-endemic area, Finca Rincon, and two high-endemic areas, Finca Brote and Finca Recreo) were analyzed. The enzymes examined were adenylate kinase (AK), alkaline phosphatase (ALP), glucose phosphate isomerase (GPI), hexokinase (HK), isocitrate dehydrogenase (IDH), leucine aminopeptidase (LAP), malic enzyme (ME), and phosphoglucomutase (PGM). Of these, six enzymes, AK, ALP, HK, IDH, LAP, and ME showed no variation either within or among populations. GPI and PGM were found to be highly polymorphic in all of the six populations. χ2-test for fit to Hardy-Weinberg equilibrium (HWE) revealed that the distribution of the phenotypes of the two polymorphic enzymes was not significantly out of the HWE. A verages of values of proportion of polymorphic loci (P) and heterozygosity per individual (H) of the six populations were 0.234 and 0.084, respectively, each of which was similar to the values reported for different groups of organisms (Nei, 1975). Genetic diversity among populations was measured by FST and GST and both parameters showed that the non-endemic population from the Finca La Ruda (Dl) was greatly differentiated genetically from the other five populations. Estimates of genetic distance (Nei, 1975) showed that the Dl population was furthest from the other populations.

DNA replication in the spermatogonial cells of Schistocerca gregaria and Gryllotalpa fossor has been analysed. This study has demonstrated the presence of at least two discrete populations of spermatogonial cells in both the insects with different intermitotic timings. The replication pattern of the sex chromosome in Schistocerca seems to be dependent on the pycnosity status, whereas, in Gryllotalpa, it is independent of the condensation pattern.

Moisture content, hardness or consistency, and age of diet were some of the properties studied for their effect on survival, growth and development of Sesamia inferens Walker. Survival of larvae was maximum on diet with 66.1% moisture. Increase or decrease in moisture resulted in excessive stickiness or dryness to the diet. Reduction in moisture content in the artificial diet was dependent on particle size of bulk constituent. Proper consistency or hardness resulting from 1.8 and 2.2% agar permitted higher number of larvae to reach pupal stage. Diet stored for 24 hr and 48 hr provided favourable conditions for the early instar larvae to establish on the diet.