Twenty-three insecticide formulations were bioassayed for toxicity against the eggs and larvae of H. hampei in maturing and ripe berries of C. arabica L. Var. typica. The infested berries were dipped in different concentrations of individual formulations, dissected 24 hr later for recording larval mortality and transferring the eggs to wet filter papers where larval hatching was recorded for the next 4 days. The order of toxicity and LC50 (% a.i. × 103) values for the eggs in maturing and ripe (figures in parenthesis) berries were: thiodan EC 35, 5.1 (6.2) > perfekthion, 5.9 (8.1) > decis, 7.2 (9.4) > carbicron, 7.3 (9.8) > actellic, 10.6(12.9) > thiodan EC 3, 14.7 (17.4); > folimat > aldicarb > dursban > tiovel > supona > dimilin > methomyl > kelthane > phosdrin > sevin > methoxychlor > dieldrin > azordrin > fenitrothion > bimarit > chlorpyrifos > gardona, 39.7−1043.7 (44.3−2642.2). The order of toxicity remained almost the same for the larvae, the LC50 values being 2.1−12.7 (2.9−21.8) for the top six and 14.8−1920.4 (47.1−2738.6) for the remaining 17 formulations. Generally, the formulations were 1.1−2.7-fold more toxic to larvae than to eggs infesting the maturing berries but 0.47−3.57 more toxic to eggs than larvae in the ripe berries.

A study of the resting site preferences of Glossina palpalis gambiensis in an area of a gallery forest in the Northern Guinea Savanna of Mali, infested exclusively by G. p. gambiensis was conducted in February, 1980 (hot dry season). Five site-types were compared: fallen logs, boles, undergrowth, tree canopies and branches. Distribution of resting flies was as follows: fallen logs (55.62%), boles (35.24%), undergrowth (8.4%), tree canopies (0.61%) and branches (0.00%). Most of the flies were collected during the periods 06.00–09.00 (37.47%) and 09.00–12.00 hr (46.5%). On boles, 86.06% of flies were found below 1.0 m and no flies were collected above 2.0 m. These results are compared to those obtained during simultaneous studies on the resting site preferences of G. p. gambiensis in an area along the same gallery forest, with mixed G. p. gambiensis and G. morsitans submorsitans infestation. Possible reasons for the differences observed are discussed.

A pair of accessory reproductive glands (ARGs) containing a variety of secretory products forms a part of the male reproductive system of the tsetse, Glossina morsitans morsitans Westwood. All of the ARG cells have an extensive rough endoplasmic reticulum which is indicative of the production of proteinaceous substances to be secreted. Histochemically, the secretory products in the lumen of the ARG contain a neutral mucopolysaccharide-protein complex, and are products of several morphological types. The latter are probably stages of maturation of the secretory materials that eventually become the wall of the spermatophore, a highly organized structure which acts as a temporary container for the spermatoza during their transfer to the spermathecae, and is histochemically composed of a mixture of carbohydrates and proteins. On grounds of histochemical and ultrastructural similarities, we suggest that the spermatophore of G. morsitans is derived, at least partially, from the male ARGs.

The distribution and importance of stem-borer species of sorghum in Kenya, viz. Chilo partellus Swinhoe, C. orichalcociliellus Strand, Busseola fusca Fuller, Eldana saccharina Walker and Sesamia calamistis Hampson were studied and discussed. The incidence and period of activity of the stem-borer complex on sorghum indicated that C. partellus, which is a major pest, infested the crop early, while E. saccharina and S. calamistis infested late and persisted in the crop till it was harvested. Preliminary studies on the carryover of stem-borer showed that the larvae of C. partellus and S. calamistis were able to enter diapause in dry sorghum stalks for several months at the end of long and short rain seasons. Some new alternative host plants and parasites and predators affecting different life stages of stem-borers were identified. Preliminary screening of several sorghum lines was carried out for identification and confirmation of resistance to C. partellus and B. fusca, and some sources of resistance were reported.

The sternal gland in Macrotermes michaelseni is located in the anterior half of the fifth abdominal sternite between the third and fourth abdominal ganglia and overlapped by the fourth sternite. It is found in all castes including newly-swarmed de-alates. The gland is largest in major workers followed by major soldiers, minor soldiers and minor workers and is the only source of trail pheromone. Major workers have the highest potential trail pheromone activity followed by minor workers, male and female de-alates, minor soldiers and major soldiers.

There is a change in trail laying behavior with time and direction of travel, from the culture or from the arena and it can be correlated with the deposition of a light or heavy trail, or no trail at all.

The trail of one major worker leaving the culture is attractive to a significant number of workers for 1 hr 30 min and that of five major workers for 1 hr 45 min. The trail of workers leaving the arena is not as strong, one worker trail is attractive for 1 hr and five worker trails for 1 hr 15 min. The well-established trail is attractive to a significant number of workers for 9 hr. All trails lose attractiveness at a constant rate.

Animals were trapped in Marigat, Baringo District to investigate animal reservoirs of visceral leishmaniasis in an endemic focus of the disease. Several species of rodents, carnivores and reptiles were captured. Specimens of spleen, liver and blood tissues were taken from the animals. The specimens were triturated into sterile saline and then cultured into NNN medium, and some of it injected into hamsters intraperitoneally. Skin biopsies were also taken and cultured in NNN medium. Slide smears of all the tissues taken were made stained with Giemsa stain and examined under the microscope for amastigotes. Four isolates of leishmanial parasites were made from a gerbil and three monitor lizards.

Three consecutive generations of Hypsipyla robusta Moore (Lepidoptera: Pyralidae) were reared on the McMorran–Grisdale Diet (MGD) medium. Mortality rates among the older larvae were consistently low (less than 1.0%) but high (up to 50%) in the first instar stage which was due primarily to escapism and non-feeding. Developmental period from egg to adult was not adversely affected by the artificial diet and ranged between 29 and 41 days. However, a comparison of numbers of larval instars and pupal sizes indicated that the nutritional quality of the MGD and natural food sources differed appreciably. A longterm study to evaluate the usefulness of the MGD for planned mass rearing programmes of H. robusta is recommended.

Three years work at Mtwapa Research Station summarises the fluctuation of Chilo spp. and Sesamia spp. Chilo partellus has been been shown to be just as important as C. orichalcociliellus nearer the coast, but Sesamia calamistis becomes important towards the second growing season.

The loss caused by these borers to maize plants in the field has been estimated to be high when no chemical treatment is applied, but such a loss varies with the intensity of infestation. Control of the borers by cultural methods relies on planting maize at the onset of rains. Selected chemical treatment at the appropriate time reduces the loss by about 20%.

By employing histological techniques, it was possible to identify 11 stages of oocyte development in adult female Sarcophaga tibialis (Diptera: Sarcophagidae). Stages 1–4 were represented by the differentiation of the oocyte and the acquisition of the follicular envelope. Stages 5–9 were characterized by a considerable growth of the oocyte which occurred due to an enormous deposition of yolk in the cytoplasm, while the follicle cells were typified by large intercellular spaces. Descriptions are given of the follicle cell degeneration during stages 10 and 11, which end with membrane formation around the mature egg.

Temperature-time and temperature–velocity equations are given for egg, larval and pupal stages of the sorghum shootfly, Atherigona soccata. Preimaginal development (from egg deposition to adult emergence) on sorghum CSH-1 seedlings lasted 19.5, 26.3, 33.8 and 76.8 days at 30, 25, 20 and 15°C, respectively. The sorghum shootfly showed optimal development and survival at 30°C. Lower threshold temperatures were 13.8, 10.2 and 11.8°C for the egg, larva and pupa, respectively. Host plant condition affected larval development and survival; pupal weight was higher and larval mortality lower in insects reared on fertilized and normally watered seedlings than on unfertilized and water stressed seedlings.

Preliminary observations were made in the attraction of moths of Chilo partellus Swin., Busseola fusca Fuller, Sesamia calamistis Hmps. and Maliarpha separatella Rag. to light traps and to traps baited with virgin females of these species. The observation was conducted from January 1981 to April 1982 at Mbita Point Field Station in western Kenya. M. separatella showed the highest attraction to light traps followed in descending order by C. partellus, E. saccharina, S. calamistis and B. fusca. The mean catches/trap/night in pheromone traps was highest for M. separatella, followed by C. partellus and B. fusca. The period of atttraction of the moths during the night and effect of moonlight on trap catches were also studied. Catches from light and pheromone traps indicated that attraction of C. partellus and M. separatella was greatest between 23:00 and 03:00hr. The effect of moonlight on light trap catches was greater than on pheromone trap catches.

The leafminer, Liriomyza trifolii Burgess, a polyphagous agricultural pest, can attack crops at different stages of development; some are attacked at the beginning of the crop cycle and others at the end of the cycle. Experiments on the differential susceptibility of the bean Phaseolus vulgaris and the potato Solanum tuberosum plants were done to get some information about factors which influence host selection by the leafminer. The distribution and density of leaf trichomes, as well as the nutritional status of the host plants, were found to be important in host selection. High trichome density acts as a physical deterrent to Liriomyza flies, just as senescing primary bean leaves induce non-acceptability. When given a choice, flies prefer bean to potato leaf discs, though the latter possess less trichomes. Other factors (chemical attractants and some nutrient components) might therefore also be involved in the complex host selection behaviour of L. trifolii.

A polytrophic ovariole of the fleshfly, Sarcophaga tibialis Macquart, is composed of two successively maturing egg chambers, each consisting of an oocyte, an interconnected cluster of 15 nurse cells, and an enveloping layer of follicle cells. The oocyte is established at the posterior end of the egg chamber. Nurse cell differentiation is characterized by nucleolar multiplication. At 25°C the first egg generation took approximately 8 days to develop. During this period, the growth rate of the egg chamber increased with time. A dramatic increase occurred during days 4–6, and was associated with the formation of large intercellular spaces between the follicle cells as well as an accumulation of numerous yolk globules. Completion of egg-chamber development was marked by the degeneration of the cluster of nurse cells and that of follicle cells.

Population dynamics of the larvae of Eldana saccharina Walker, Chilo zacconius Bleszynski and Sesamia spp. on sugar-cane was studied over a period of 3 years, by regular sampling. Analysis of results indicated that during the first rainy season (March–June) the borer populations were low. However, the larval population increased considerably during the dry season and declined gradually during the second rainy season (September–November). Rainfall in Southern Ghana is typically bimo-dal, but it is occasionally evenly distributed throughout the year. When rainfall was evenly distributed. borer populations remained consistently low throughout the year. Flooding reduced the population of E. saccharina larvae in the field. Though the stem-borers showed preference for relatively younger canes, the type of borers present and their proportions varied with the sugar-cane phenology.

In a recent review of host location by tsetse an attempt was made, using previously published data, to draw some general conclusions regarding the range of detection of warm-blooded hosts by tsetse and mosquitoes. The paper included some misleading and invalid conclusions. This topic and the supporting data are reconsidered. It is suggested that the maximum range of a positive response by mosquitoes or tsetse to stationary cattle baits may be expressed as 0.31 × host weight (kg)0.90 (P < 0.001).

Anthropophilic phlebotomine sandfly, Phlebotomus heischi, has previously been reported in Kenya by Kirk and Lewis (1950). Only one sandfly (female) specimen was reported. The present paper reports and redescribes the male form of P. heischi from Kalawa, Machakos District, Kenya, a region of a recent epidemic focus of visceral leishmaniasis.

At harvest taller plants of both sorghum and maize produced a greater grain yield, but under intercropping conditions maize always out-yielded sorghum when planted at the same time, whether the sorghum was planted in the same hill as maize, or in alternate hills, or in alternate rows. There were generally more stem-borers in sorghum than in maize, with Chilo partellus predominating. Intercropping increased the level of stem-borers in maize, while infestation was very low in pure stands of maize, and the level of borer infestation in sorghum remained the same. Borers had a considerable effect on yield of maize at Mbita Point, on the shores of Lake Victoria: an infestation level of 38–52% of internodes bored resulted in significant yield loss. Implications of these results for predicting yield reduction due to stem-borers is discussed.

Investigations were carried out on the origin of osmeterial secretions exuded by fourth instar larvae of Papilio helenus and P. protenor that had been reported to secrete a variety of terpenic compounds. Variations in the chemical composition of the secretion induced by dietary and/or genetic factors were quantitative rather than qualitative in both species. Overall pattern of the chemical constituents was found to be highly species-specific and substantially invariable in a given species. Several sesquiterpene hydrocarbons secreted by the larvae were not present in detectable amounts in the leaves of the host plant, Fagara ailantoides, suggesting that the sesquiterpenes were biosynthesized by these larvae. Deuterium was efficiently incorporated in vivo into sesquiterpene hydrocarbons in the secretion, (E)-β−farnesene, β−caryophyllene, germacrene-A and germacrene-B, by topical application of deuteriumlabelled acetic acid to everted osmeteria, while similar treatment with deuterium oxide resulted in much lower incorporation of deuterium. These results provide evidence for de nova biosynthesis of sesquiterpene hydrocarbons in young Papilio larvae.

The present article considers quantitative assessment of crop losses in relation to attack by three trophic levels of insect pests on maize, cowpea and sorghum intercropping systems. The trophic levels considered are (i) specialist feeders subsisting only on one crop within the intercropping systems, e.g. Maruca testulalis (Geyer) on cowpea, and Atherigona soccata (Rondani) on sorghum; (ii) the relative specialist feeders subsisting on two out of the three crops e.g. Busseola fusca (Fuller), Chilo partellus (Swinh.) Sesamia calamistis (Hmps.) and Eldana saccharina (Wlk.) feeding on maize and sorghum cereal plants; and (iii) the generalist feeders e.g. Heliothis armigera (Hbn.) which feeds on all three plant species. Tests for loss assessment were done under natural field conditions within maize, cowpea, sorghum monocropping patterns; maize–cowpea, maize–sorghum, sorghum–cowpea dicropping patterns; and the maize–cowpea–sorghum tricrop intercropping patterns. The authors discuss in detail their modified analytical methods based on the comparison of yield of sets of plants growing under identical conditions except that one set is unattacked by the stem-/pod-borers and the other set attacked, to generate economic losses. The comparative advantages of the planting systems on crop turnover is further discussed. The biomass and plant population fluctuations caused by pest attacks and ‘dead hearts’ at differential time scales in indices of yield have also been discussed. Yield per unit area of monocrop and intercropping patterns have been contrasted using the yield turnover of monocrop plant equivalence as the baseline for comparisons. Maize–cowpea–sorghum mixed intercrop of 1.45 land equivalent ratio (LER), and that for the sorghum–cowpea dicrop with 1.3 LER are considered the most advantageous cropping patterns. Yield losses significantly higher (P < 0.05) within maize-sorghum intercropping combinations with 0.89 LER further suggests that stem-borer colonisation which occurs at an earlier stage of crop establishment resulting in ‘dead hearts’ and significant reduction on plant population per unit area within the two cereal combinations contribute significantly to the overall reduction in crop turnover within such mixtures.