The effect of some rice varieties on the biology of the stalk-eyed fly Diopsis thoracica West was investigated. The rice varieties affected the developmental period from egg laying to adult emergence, the sex ratio, percentage survival, adult weights on emergence, ovary development and the rate of tiller damage by a single larva. The rice varieties OS6 and Tos 4121 were consistently the most unfavourable in terms of insect growth; but were the most susceptible in terms of damage. Thus varietal susceptibility to damage by the insect seemed to be different from varietal suitability for its growth.

The salivary gland of Glossina morsitans contains cholinesterase activity which is distributed in a network surrounding each epithelial cell of the secretory region. The enzyme does not appear to be associated with any neural structures and is similar to cholinesterases of most insects in its reaction with inhibitors and in its ability to hydrolyze a wide range of substrates.

The pest complex of sunflower and its relative abundance and economic importance are discussed. A total of 80 insect species were collected—five of these were recorded on roots, 51 on stems and leaves and 29 on floral parts and developing seed. The major pests of sunflower commonly encountered in all the localities studied were Agrotis segetum Schiff, Agrotis ypsilon Hfn, Plusia orichalcea F., Nezara viridula L. and Heliothis armigera HB.

The effects of virginity on feeding and milk-gland (MG) activity were investigated in 4-week-old virgin females of Glossina austeni. The flies take in smaller but constant amount of blood roughly equivalent to their own weight during each feed. This syndrome of feeding to a constant weight with time leads to fatbody hypertrophy largely because of decreased metabolic demands due to the absence of a larva. It is suggested that the small blood-meals of virgin females are probably related to the space limitations in their abdomens, and are probably hormone-mediated, possibly operating via the cuticle. The MG of virgin flies is well-differentiated but the cycles of synthetic activity which the distal MG tubules exhibit in mated flies during a pregnancy cycle are not so apparent in virgins. The secretions of this gland are used to nourish the developing larva and if the MG were very active the secretions produced would be lost. It is concluded that in virgin females the blood-meal is reduced in size, probably as a result, at least partly, of a reduction or absence of neurosecretory out-flow related to mating and ovulation, and the products of their blood-meal apparently are diverted not to the MG but to the fatbody for storage. These effects of virginity on blood-meal size, fatbody and MG activity can be reversed at any time by mating.

The trends in flowering, podding and seed yield of four cowpea varieties planted at different times of the growing season in 1975 and 1976, were studied along with the associated pest activity. Flowering, podding and seed yield were found to decrease over the season from April to September irrespective of whether the crop was protected against insect pests or not. However, there seemed to be two peak periods of pest activity—April to July and October to December—when severe damage to the crop occurred in unprotected plots. Planting in June or July usually led to an escape from several major pests even though the cool night temperatures and incidence of overcasts at that period seem to preclude optimal reproductive performance of the crop.

The pattern of insect pest succession on the crop over the season is discussed and it is suggested that for small farm holders in Southern Nigeria, who are unlikely to apply insecticides, planting in June is advisable.

Third- or fourth-stage nymphs of the large milkweed bug Oncopeltus fasciatus (Dallas) were maintained for 2–5 months on a chemically defined diet. Four or five per cent of either sucrose, glucose or melezitose gave better growth than 11 other sugars tested. The insect required the 10 amino acids usually recognized as essential for growth in other insect species. The dietary concentration of each essential amino acid was varied over a wide range of 6–12 or more times without affecting growth in a significant manner. Growth improved as the total amino acid concentration was increased from 0 to 1.2, 1.8, 2.4 and 3.6%, but a further increase to 4.8% did not result in an improved growth. Fifth-stage nymphs maintained on chemical diets moulted to the adult stage and laid eggs for several months; the average number of eggs per female was 62 on the 1.2%, 143 on the 2.4%, 131 on the 3.6%, and 69 on the 4.8% amino acid diets. No eggs were laid on a diet lacking amino acids. Growth and survival of nymphs reared singly on the diet were reduced as compared to that of nymphs reared in small groups. A quarter to half reduction in the concentration of the two major dietary salts, as well as a reduction in the pH from 7.0 to 6.0 or 5.0, or an increase to 8.0 improved growth.

Field-trapped tsetse Glossina pallidipes, G. brevipalpis and G. austeni were dissected and the incidence of hypertrophy of the salivary glands (HSG) recorded. This condition was observed only in G. pallidipes. The highest level of infection (15.6%) was observed in July in one of the trapping sites. Both very young teneral (ovarian category 0a) and very old (ovarian category 7 + 4N) tsetse had greatly enlarged glands. The differences in bi-monthly HSG incidence for the five trapping sites were statistically significant. The level of infection in males and females did not show significant differences.

Neuroendocrine mechanism involved in pupal colour dimorphism in Papilio xuthus L. has been studied using ultrastructural techniques. The browning hormone in the form of neurosecretory material is secreted in the brain during the larval stage and transported to the axonal endings in the prothoracic ganglion, irrespective of the colour of the future pupa. If larvae select for pupation environmental conditions that are conducive for the formation of a brown pupa, release of the browning hormone occurs in the middle of the prepupal stage. No release occurs in larvae that have selected environmental conditions that favour the formation of green pupae. It is suggested that the brain, having integrated and interpreted the environmental conditions selected by the larva for pupation, gives the order to release the browning hormone. Such an order is conveyed via neural path from the brain to either the prothoracic ganglion, or some still unknown neurohaemal organ associated with it, from which release then takes place.

The incidence of cuticular lesions on the ventral abdominal integument of the tsetse Glossina pallidipes, G. Brevipalpis and G. austeni was monitored by trapping over 12 months in four localities along the Kenyan coast. Four types of lesions were observed: necrotic pits, necrotic warts, necrotic striations and necrotic discs. Necrotic discs were most prevalent, and up to 30.5% of female tsetse had this type of lesion. The differences in cuticular lesion levels on flies trapped in the dry and wet seasons were not significant. There were no significant differences in the proportions of tsetse with lesions sampled at different sites. Females had a significantly higher proportion of necrotic pits, necrotic warts and necrotic striations than males but the level of necrotic discs on males and females were the same. Histological examination of tissues did not demonstrate any causal association between lesions and infectious microorganisms. There was no correlation between the presence of cuticular lesions and hypertrophy of the salivary glands, a pathology associated with virus-like particles in G. pallidipes.

Investigations were carried out on the seasonal population fluctuations of the moth Cydia ptychora. The population increased from May to September and declined from November to April. Increasing temperatures and decreasing r.h. appeared to be associated with population decline, while the reverse seemed to favour population increase.

From light trap catches, sex ratios of adults showed considerable variation from month to month. The overall ratio was 2:1, in favour of the males, but there was a tendency for adjustment towards an apparently female-biased ratio from March to August.

Bracon (?) hancocki was found to be a major parasite. Other biotic factors contributing to population regulation included 13 hymenopterous parasites and three predators (Philodicus temerarius, Bactria sp. nr. guineensis and Chrysopa sp.)

Nilaparvata lugens (Stål) biotype 1, 2 and 3 populations maintained as stock cultures for several years showed distinct morphological segregation based on multiple discriminant analysis using Wilk's Lambda method. Morphological characters of the rostrum, legs and antennae of both brachypterous and macropterous males and females provided a significant degree of certainty in classifying the three biotypes. The predicted biotype composition of the brown planthopper populations formed separate clusters.

Investigation of sandfly vectors of visceral leishmaniasis (kala-azar) was intensified after the epidemic outbreak of the latter in Machakos District, Kenya, in the early 1970s. Studies were carried out to assess the infection rate of potential vectors using human baits during the height of the 1978 epidemic outbreak. The results presented here indicated that, in Machakos District, sandflies captured when coming to human baits had higher infection rates than those collected in the natural resting sites using suction tubes.

The detection of household infestations of Triatominae in regions endemic for Chagas' disease is a criterion frequently used in the selection of areas, or of individual houses, for treatment in insecticide campaigns as well as for the evaluation of insecticide performance.

Several methods for the detection of domestic infestations with Triatominae were compared: diurnal capture of live bugs with the aid of a flushing-out agent, night-capture without using flushing-out agents and the use of cardboard boxes of the the Gómez-Núñez type. The flushing-out and Gómez-Núñez box methods were found to be equally sensitive, although each gave several houses as uninfested in which infestation was detected by the other method. The night-capture method was slightly more sensitive but was found to be impractical for large-scale surveys. Improvements to the flushing-out method, notably the introduction of a systematic search technique, made it much more sensitive than the Gómez-Núñez box method for both heavily infested houses and for houses 3 months after insecticide treatment.

Coating the inside surfaces of the boxes with adhesive did not increase the sensitivity of this method and, although this can be achieved by leaving the boxes in place for long periods of time, this also limits the value of the information thus obtained as regards the evaluation of insecticides. On the basis of the results presented, the flushing-out method using a systematic search of the house was found to be the most suitable sampling technique, but it is recognized that this method still has limitations.

The previously unknown male of Sergentomyia blossi (Kirk and Lewis) is described and illustrated. It differs from S. yusafi (Sinton) and S. ruttledgei (Lewis and Kirk) mainly in details of the cibarial armature. Further information on the structure of the S. blossi female is given. Specimens were collected in rock crevices near Rabai, Kenya.

The structure and size of the eggs and layers of eggshells of some ticks of veterinary importance in Nigeria were studied. The ticks included Amblyomma variegatum, Boophilus decoloratus, B. geigyii, Hyalomma impressum, H. impeltatum, H. truncatum and H. rufipes. The embryonic development of the eggs from the day of oviposition to hatching was also studied.

The freshly laid egg was found to possess 10 protuberances, and the biggest of them are the anterior and posterior ones. The eggs of A. variegatum were found to be the longest, and those of H. truncatum the shortest. The eggshell of all the species is two-layered on one lateral side and three-layered on the other; the middle layer originating from the anterior and posterior protuberances. Several phases of embryonic development are described. The major difference between the embryonic development of the eggs of A. variegatum and that of the others is that there are always phases during which the egg becomes canoe-shaped and later folds back to the normal egg shape. Eggs of B. decoloratus occasionally developed this way as well as those of some Hyalomma species when incubated at 37°C. The period of accomplishment of each phase of development was shortened by high temperatures. Observations on the occlusion periods of various types of eggs showed that the very small eggs would not hatch into larvae. The relevance of these observations to field tick control is highlighted, while the necessity of following up these studies with electron microscopic views of some aspects of the results is stressed.

The lengths, breadths and areas of eggs oviposited at different times by female ticks (Amblyomma variegatum) of weight 2–3 and 0.5–1 were compared. The hatching patterns as well as mortality rates of different ovipositions of female A. variegatum of weight 2–3 g were studied at various incubation temperatures.

The eggs produced by female ticks of A. variegatum of weight 2–3 g were generally longer and broader, with a greater area also than those produced by female ticks of weight 0.5–1 g. The hatching pattern was influenced only by temperature and not by the order of oviposition of the eggs. The period of completion of all hatchings and the day of peak hatching vary according to the temperature at which the eggs were incubated. The occlusion periods of the eggs varied with their order of oviposition. It was longest in the first oviposition and shorter in the subsequent ones. Temperature also influenced the rate of mortality of the eggs. Mortality was low among eggs incubated at 24°C and rotational temperature.