When the compound eye of the adult of the planthopper, Myndus crudus, is light-adapted, pigments are condensed in a zone proximal to the crystalline cones. Viewed externally, the eye is straw-colored. When dark-adapted, pigments migrate distally into the region of the crystalline cones and thus are closer to the cuticle. Viewed externally, the dark-adapted eye is maroon-colored. The eyes of most adult M. crudus observed during daylight hours were light-adapted. Eyes of males and females changed from the light to the dark-adapted condition between sunset and ½hr after sunset. When planthoppers with light-adapted eyes were placed abruptly into darkness at a temperature of 25–27°C, the eyes became dark-adapted within 15–30 min. When planthoppers with dark-adapted eyes were placed abruptly into light, the eyes became light-adapted within 30–60 min. At 8°C the planthoppers were immobile, and light-adapted eyes had not changed to the dark-adapted condition within 45 min. Eyes of M. crudus nymphs, which live in the root zones of grasses, are dark red and do not change color in response to changes in light. Field samples showed that adult M. crudus were active in coconut palms during the day and night, but higher numbers were caught during the day (P < 0.01).

Part of the female reproductive system of Glossina morsitans morsitans Westwood (Diptera: Glossinidae) consists of two spermathecal glands each with a duct and receptacle. The receptacle is composed of secretory cells with the normal secretory apparatus (secretory vesicles, rough endoplasmic reticulum, mitochondria and microvilli), as well as bundles of microtubules. The extensive rough endoplasmic reticulum is indicative of the production of proteinaceous substances. On the basis of histochemical tests, the material in the epithelium and lumen of the spermathecal receptacle appears to be a mixture of carbohydrate and protein. These materials accumulate in cavities within the epithelial secretory cells, and are then transferred to the main lumen of the receptacle in which sperm are also stored.

The sternal gland shows significant differences in size and activity in different instars of the worker caste of Trinervitermes bettonianus. Gland size (volume and surface area) was not significantly different between instars 1 and 2, and 2 and 3; but was significantly different between these age groups and instars 4–7. The potential trail-laying activity of the gland of a worker increased from zero to 50 trail units in the course of development from the first to seventh instar. The relatively high biological activity of the gland in the older instars 5–7 may be of ecological significance, since these stages were found to constitute over 90% of foragers under field conditions.

Wild-caught phlebotomine sandflies were captured from rock crevices and termite hills and released into feeding cages containing various species of laboratory animals, to find suitable hosts for feeding flies for experimental or breeding purposes. Flies captured from rock crevices did not feed as well as those human-baited at termite hills. The ubiquitous species from the termite hills was Phlebotomus martini, the major vector of kala-azar in the study area (Machakos District of Kenya). This anthropophilic species feeds readily on the mammalian laboratory animals. Cooling flies before feeding stimulated them to feed.

The results of this experiment, where insect defoliation was simulated by artificial defoliation, suggest that Pinus kesiya and P. oocarpa trees in Zambia survive after complete defoliation, and that the reduction in growth may remain economically tolerable.

In a bluetongue (BT) disease project, light trappings of Culicoides were conducted in 19 localities and 39,000 biting midges were examined. BT virus type 16 was isolated in 1968 at Devora from a pool consisting mainly of Culicoides schultzei gp and C. imicola; BT virus type 4 was isolated in 1969 at Yesodot from a pool of 183 C. imicola; BT virus type 2 was isolated in 1979 at Talmé El'azar from pools consisting of 2462 C. imicola; and BT virus type 6 was isolated 3 times in 1980 at Bet Dagan from pools of 204, 258 and from 143 C. imicola, respectively. In the Akabane project (1976 and 1977) 4632 Culicoides and 1867 mosquitoes from four localities were trapped and examined. An arbovirus which was not Akabane, BT or turkey meningo-encephalitis (TME) was isolated from a pool of 44 engorged Culex pipiens complex trapped in Gan Shemuel. In the Rift Valley fever project, which was conducted in 1978 and 1979 due to the presence of an epidemic in Egypt, 351 mosquitoes of four species and 7098 Culicoides of 14 species were tested and none were found to harbour an arbovirus. Within the TME project more than 12,000 Culicoides and 9000 mosquitoes from 14 localities were tested. Positive isolations of TME were made from an unsorted pool of mosquitoes from Gesher haziw, an unsorted pool of 13 Culicoides from Nahalal, a pool of 223 unidentified Culicoides from Zetan and a pool of 12 engorged Cx pipiens complex from the same locality. Other pathogens which were not identified to species level were also isolated.

Following the 1978 epidemic of yellow fever in The Gambia, the distribution of the potential vector, Aedes (Diceromyia) furcifer/taylori group, was studied during the 1979 rainy season. Evening biting catches conducted in villages throughout the country revealed that A. furcifer/taylori was the most abundant vector biting man in the east of the country where the 1979 epidemic had its focus. Taxonomic studies showed that only A. furcifer and not A. taylori was present.

The structure and function of the male accessory reproductive gland system of the cotton stainer, Dysdercus fasciatus Signoret, was studied using ultrastructural techniques. The gland system is composed of a pair of mesadenia and an ejaculatory duct, whose anterior end is swollen and encloses a glandular structure whose origin is not clear. Each mesadene is composed of a large number of sacs whose lumina are confluent. The epithelium of each sac is one cell layer thick and is composed of two cell types, mononucleate and multinucleate cells. The origin and siginficance of the multinucleate condition in the mesadenial epithelial cells is not clear, but it is suggested that this condition might have arisen during maturation, when mitotic divisions are complete, but the nuclei continued to multiply within an increased cytoplasmic mass, which itself does not divide.

Three morphological classes of haemocytes (prohaemocytes, plasmatocytes and granulocytes) were observed in the haemolymph of Glossina morsitans morsitans and G. pallidipes. In addition to the three types, a category of spindle cells were also observed in haemolymph especially in the newly emerged Glossina. Based on their unusual morphology, as well as on their inverse relationship with the number of thrombocytoids (a filamentous plasmatocyte), it is suggested that these spindle cells might be precursors of thrombocytoids observed mostly in older Glossina. The number of thrombocytoids increased progressively with the increasing age of the flies. Total haemocyte counts (THCs) dropped significantly during the first 48 hr following emergence, after which the values levelled off with the exception of minor fluctuations. This sudden drop in THCs resulted primarily from a remarkable decrease in the number of the spindle cells in the haemolymph. The number of round plasmatocytes decreased gradually and progressively with age of the flies, while the number of the granulocytes increased, suggesting a possible transformation of plasmatocytes into granulocytes. Newly emerged female G. morsitans morsitans were observed to have significantly higher THCs (P < 0.01) than males of the same age. Although no difference was observed between THCs of 5-week-old pregnant and non-pregnant female G. morsitans morsitans, the differential haemocyte counts (DHCs) showed that the concentration of thrombocytoid fragments was significantly lower (P < 0.01) in the pregnant than in the non-pregnant females.

The sex-stimulant contact pheromone present in the cuticle of female tsetse Glossina pallidipes Austen has been extracted with hexane, separated by preparative gas chromatography and identified by mass spectrometry. The aphrodisiac, consisting of 13,17-dimethylpentatriacontane and 15,19-dimethylpentatriacontane, is present in cuticular extracts of 1-week-old females and, in lower amounts, in teneral females but it is almost absent in males of all ages. Full copulatory responses to hexane-washed dead males treated with the two dimethylpentatriacontane isomers were induced in 10–20-day-old adult male G. pallidipes. The practical uses to which this discovery can now be put—towards the mass-rearing and control of G. pallidipes— are discussed in detail.

Investigations are reported on oviposition habits, development, and emergence patterns of the pre-adult stages of Aedes (Stegomyia) africanus (Theo.) under laboratory conditions. It was observed that water or at least a wet surface is necessary for oviposition and that the intensity of egg-laying takes place within 2 cm from water surface and is greater in those containers with deeper water levels. Post-oviposition embryonic development lasts an average of 6 days thus conforming with earlier findings (Gillett, 1955). The quantity of water does not affect either the period of post-oviposition embryonic development or the rate of egg hatching. However, an average of 75% of the eggs hatch within the first 13 days after flooding, leaving the rest to hatch in subsequent instalments. At 27°C, the second-instar larvae take the shortest time to develop while the fourth-instar larvae take the longest period. Generally, intra-instar variability in growth rates were observed except in the pupal stage. Emergence of the various pre-imaginal stages and pupation did not appear to have any regular periodicity. Of particular interest was the observation that the number of instars in this species varied from the normal number of four, a finding which is believed not to have been recorded previously in the family Culicidae.

Observations were made on the tsetse species Glossina longipennis Corti in Nkruman escarpment, Kenya. The species inhabited relatively open areas of the bushland. The rate of infection with trypanosomes was studied as well as the activity pattern and amenability to trapping. Results of laboratory rearing are given. Trypanosome infection rate was higher in female flies than in male ones. The method of using a slow moving vehicle, resulted in the capture of more old flies than young ones—of both sexes—and more males than females. G. longipennis was not amenable to trapping by any of the two mechanical traps used (Moloo's trap, and the biconical trap of Challier and Laveissiere).