Studies on aspects of the biology of the kola weevil Balanogastris kolae on Cola acuminata and C. verticillata were made in the laboratory at temperatures of 28–30°C. Mated females of B. kolae oviposited a significantly higher number of eggs (238) in C. acuminata than in C. verticillata (205) when confined separately with the nuts. But when the weevil was offered the choice of three Cola species as oviposition media, significantly more eggs were oviposited in both C. nitida and C. verticillata than in C. acuminata. However, there was no significant difference between the number of eggs oviposited in C. verticillata and C. nitida.

The average total incubation, larval and pupal developmental periods of B. kolae in both C. nitida and C. verticillata were 6, 16.2 and 6.1 days, respectively. The average total developmental period in C. acuminata was 28.8 days, and 26.5 days in C. verticillata. Although the total developmental periods overlap, there was a significant difference between the periods of development of B. kolae in the two Cola species. Oviposition and development of B. kolae in the wild species, C. verticillata, coupled with its wide distribution show that it may be ecologically important in the survival of the weevils, especially when the cultivated Cola species are not available in the field.

The oviposition site preference of the legume pod-borer on cowpea plants was studied under screenhouse conditions using an egg marker technique. Flowers, flower buds and abscission scars were found to be the most preferred sites. The results obtained in the screenhouse tests were in general agreement with those obtained under field conditions where presence of young larvae (first and second instars) was used as the indicator of oviposition sites.

The pupal parasitoid Xanthopimpla stemmator Thunberg oviposits in the pupae of the spotted stalk borer (or sorghum stem borer) Chilo partellus (Swin). The adult parasitoid emerges from the pupal case, killing it in the process. Ten mated females of the parasitoid had an average longevity of 30 days (maximum 37 days and minimum 22 days). The number of progeny produced ranged from 71 to 115, with an average of 84.5. The male:female sex-ratio of their progeny averaged 1.14:1. The maximum mean progeny production per day (mx) was 1.9. The innate capacity for increase was 0.131 per female per day; and the population multiplied 43.43 times in the generation time of 28.78 days.

Purified suspensions of macerated cuticular lesions from the insectary-reared tsetse Glossina morsitans morsitans were applied on laboratory-reared newly emerged teneral tsetse by three pathways: topical application on the ventral abdominal integument, oral microfeeding, or microinjection into the haemocoel. A second group of flies were subjected to teratological wounding pin-stabs, forcep-pinch and shallow blade-slits, all in attempt to induce cuticular lesions. Samples of tsetse were examined every week for 11 weeks. Application of cuticular lesion suspensions did not result in lesion formation, but three types of lesions were formed due to physical damage induced artificially on the integument.

Total haemocyte counts (THCs) and differential haemocyte counts (DHCs) were also determined for tsetse with, and without, lesions. THCs were significantly higher (P < 0.01) in tsetse with cuticular lesions than in those without lesions. DHCs showed a high number of large spindle-shaped cells and thrombocytoids in the flies with lesions (P < 0.05).

Teneral nulliparous tsetse Glossina pallidipes were infected with virus-like particles by two pathways: haemocoelic microinjection, and oral feeding with a micropipette. Samples of tsetse were dissected every 3 days; and at 22 days post-infection, cumulative per cent infection was 44.4 and 31.3% for microinjection and per os infection, respectively. Natural virus-like particle infection in the population was 3.6%. Thus the infectious nature of virus-like particles was established, together with two possible pathways of infection.

During three seasons of observations similar populations of the jassid Empoasca lybica were recorded on two different eggplant cultivars (cvs). However cv Black Beauty exhibited more tolerance to jassid attack than cv Long Purple. Comparing jassid-infested and jassid-free treatments, the growth and yield of Long Purple plants were reduced more drastically by the insect than were those of Black Beauty.

The LC50 values (% active ingredient in parentheses) for 34 formulations of 29 insecticides, obtained by dipping green berries (GWB) infested with adult Hypothenemus hampei, were: thiodan EC 35 (0.0003) > perfekthion (0.0004) > carbicron (0.00044) > decis (0.0005) > actellic (0.0008) > basudin (0.0009) > belmark and ciodrin (0.0012) > thiodan EC 3 (0.0013) > malathion (0.0014) > folimat and bidrin (0.002) > aldicarb and lindane (0.003) > nexion > tiovel EC 3 > dursban (0.0046–0.006) > supona > methomyl > kelthane (0.011–0.012) > chlordane > aldrin > dimilin > chlorfenvinphos > phosdrin > sevin > methoxychlor > dieldrin (0.016–0.025) > nexagan (0.034) > azodrin (0.04) > fenitrothion (0.07) > bimarit (0.14) > chlorpyrifos (0.39) > gardona (0.96).

The order of toxicity remained the same for borers in the pulp (GP) or endosperm (GE) of green berries or endosperm of red (RE) berries, though the LC50 of each formulation of the same or different insecticides varied significantly. The respective LC50 values for the four leading, and the rest of the formulations were about 7−21- and 2−6-fold higher in GWB than GP, 9−23 and 2−5-fold higher in GE than GP, 1−2.3- and 1−3-fold higher in RE than GE, and 12−25- and 3−37-fold higher in RE than GWB. The practical significance of the results is discussed.

Data on the populations of larval and pupal stages of Aedes africanus, an important sylvan vector of arboviruses, were collected from tree-holes which are its natural breeding sites in forests. Comparable data were also simultaneously collected from bamboo pots stationed in the Zika Forest to simulate the natural breeding sites. Survivorship curves and time-specific life-tables were constructed. It was observed that the immature stages of A. africanus in both tree-holes and bamboo pots suffered very high mortality rates (an average of 91% in tree-holes and 83.2% in bamboo pots). It was further observed that mortality rates varied monthly. The survivorship curves constructed for the immature stages collected on a daily basis tended to show that a large proportion of the mortality rate was confined to the early instar stages, but the survivorship curves based on the combined data for the 2 years indicated constant mortality rates for all the stages. The high mortality rates of the immature stages of A. africanus appear to be attributed to predation by larvae of Toxorhynchites brevipalpis, with which it shares the same breeding places.

Ultrastructural studies were carried out on wild Kenyan sandflies (Phlebotomus pedifer) naturally infected with Leishmania aethiopica. The promastigotes were attached to structures resembling pieces of a peritrophic membrane. They were located amongst long microvilli and also deep in the cytoplasm of the gut cells. The factors which influence the invasion of the parasites into cells are not known and need to be investigated.

Phlebotomus martini, a sandfly belonging to the Synphlebotomus group, is the main vector of the fatal disease kala-azar in Kenya. The breeding sites of this species have so far remained a mystery, and immature stages have not yet been observed in nature. Collection of adult P. martini was done through human-bait. Immature stages, obtained from these catches, were reared to the adult stage in the laboratory for the first time. The size and the rate of development of the various stages were studied at 27°C and 100% r.h. The mean duration from egg to adult was 56.1 days. Observations were made on the biting behaviour of sandflies during human-baiting. Preliminary observations of natural enemies encountered in the rearing cages are described.

Nutritional efficiency of four dehydrated and powdered tapioca puddings for Tribolium confusum (duVal) was assayed by studying growth, survival and fecundity of the confused flour beetle on these diets.

The common pudding inflicted about 50% mortality and caused over three-fold growth retardation in the larvae. The longevity and fecundity of the adults also were significantly reduced (P < 0.01). On the other three test puddings which contained less vitamins and more fat or carbohydrate than the common pudding, growth was even more severely retarded, and only 9% of the larvae became adults of doubtful reproductive ability. Results obtained from puddings supplemented with vitamins, or made with synthetic milk in which vitamin and fat levels were manipulated, suggest that the nutritional inadequacy of the four test puddings was mainly due to low vitamin and high fat contents.

The results demonstrate the practicality of inducing ‘self-protection’ against insect pests in certain types of food products without seriously affecting their acceptability by man.

Animal-infective forms (metacyclics) of Trypanosoma brucei brucei were grown in continuous culture at 29°C from the salivary glands of infected tsetse. The parasites were found by immunofluorescent staining to be antigenically stable in the course of cultivation. When the antigenically stable parasites were incubated at 37°C they transformed from long and thin forms to short and stumpy ones and finally to long and slender parasites. The latter generated antigenic variants starting from the second, third or fourth week of incubation at 37°C. Once antigenic variants appeared at 37°C it was not possible to restore the parasites back to antigenically stable populations when they were transferred back to 29°C. These findings may have far-reaching implications in the study of antigenic variation in pathogenic African trypanosomes and the possible development of immunizing reagents against tsetseborne trypanosomiasis.