Research on stem borer pests of sugarcane, maize and rice in Ghana is briefly reviewed. The work on the biology of the borers carried out at Asutsuare between October 1977 and January 1980 has pinpointed the fact that the practice of ratooning is the principal cause of a devastating build up of stem borers in the sugarcane fields. Cost/benefit analysis has revealed that as a result of discontinuation of this practice, there would be an initial gain of $13.4/ha. The profit should increase in subsequent years when the foci of borer infestations are removed as a result of the discontinuation of ratooning. The use of imported parasites as well as insecticide treatment in controlling the borer populations has been ineffective. Further work in developing novel control measures against sugarcane borers is still in progress. Only cultural methods have been found useful in limiting the damage caused by stem borers to maize. Losses caused by stem borers to the rice crop in Ghana are still not well established.

This paper reviews work on techniques in mass rearing of insect pests, especially stem- and pod-borers. The account covers advances in rearing of insects on native host plants and on artificial diets and possible ways of use of these insects in host plant resistance research.

The literature published during 1970–1981 on tsetse ecology is reviewed. The geographical distribution of some species was affected during the drought of early 1970s. New maps of tsetse distribution in Africa and a few national maps have been published. The habitats of several species have been described in detail, particularly atypical habitats in peridomestic situations. Pupal ecology has not held the attention of ecologists so much; however, pupal duration and mortality have been assessed for a few species. Due to the importance of selective application of insecticides, resting sites and resting behaviour have been described in detail. Activity patterns have been correlated with climatic factors and also with sampling methods. Several works on host-seeking behaviour, flight performance and energy metabolism have been described. Host preferences of certain species have been found to be somewhat different from those previously recorded; and new host species have been discovered. Studies on fat and haematin content showed that these metabolites are useful indices of nutritional status to interpret feeding behaviour in relation to population sampling. A tsetse contact sex-pheromone has been discovered and synthetised; and attempts have been made to use it in the field. Studies on sound production by both sexes under various conditions of light and physiological state are in progress. Comparative studies on sampling techniques have received particular attention; several trap devices have been designed and tested to evaluate the reliability of samples. The determination of the age structure of populations has become more relevant to studies on population dynamics. Attempts have been made to calculate the growth rate of populations. Density-dependent factors started being taken into consideration in the assessment of populations. Several methods have been tried out to estimate population size. New pathogens, parasites and predators have been recorded.

Four species and subspecies of rats and mice (Rattus norvegicus, Arvicanthis niloticus niloticus, Mus musculus and R. r. frugivorus) were found associated with a new irrigated area, El-Galaa, about 55 km from the edge of the desert near Alexandria, Egypt. Ectoparasites recovered from these hosts were three species of fleas (the Oriental rat flea Xenopsylla cheopis Rothschild, the human flea Pulex irritans Linnaeus, and the cat flea Ctenocephalides felis felis Bouche). three species of sucking lice (Polyplax spinulosa Burmeister, Polyplax abyssinica Ferris, and Hoplopleura capitosa Johnson), and five species of mites (Ornithonyssus bacoti Hirst, Laelaps keegani, Dermanyssus spp., Haemolaelaps spp., and Echinolaelaps echidninus Berlese). Records showed that the lice were the most abundant ectoparasites (39.03%) recovered from their rodent hosts, followed by the mite species (36.82%) and finally the fleas (24.1%). Lice in general and fleas (especially X. cheopis) showed a certain degree of host specificity as compared to other ectoparasites. A close correlation has been shown to exist between the incidence of flea and lice species (but not the mite species) and the incidence of some rodents.

Resting site preferences of the tsetse Glossina morsitans submorsitans Newstead were studied in a savanna woodland and gallery forest in the Northern Guinea Savanna of Mali. Five site-types [boles, fallen logs, undergrowth (‘bushes’), branches and tree canopies] were observed. Flies alighting to rest on these site-types were trapped on tanglefoot. Observations were made in the warm rainy, warm dry and hot dry seasons.

Boles were dominant as the preferred resting sites in the savanna woodland in all seasons; fallen logs were the next preferred site-type, while few flies were collected from the undergrowth, branches and tree canopies. Approximately 90% of flies on boles were collected below 1.0 m and none were found above 2.5 m.

During the hot dry season in the gallery forest, the undergrowth was the most preferred site-type; unshaded undergrowth accounted for approximately 98% of all flies on the undergrowth. Fallen logs and boles were the next preferred site-types; branches and tree canopies recorded very few flies. Probable reasons for the results obtained and the importance of these results in tsetse control operations are discussed.

In choice tests with well-established natural trails and glandular extract trails, allopatric populations of Trinervitermes bettonianus Sjöst followed alien colonies' trails with the same degree of motivation as their own trails. The five Trinervitermes spp. tested readily followed each other's trail. Chromatographs of natural trail extracts showed that the main component of the T. bettonianus trail pheromone also occurs in trails of T. gratiosus (and presumably in the other species); this would account for the observed cross-following of trails among these species.

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.

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.

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.

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 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.

Preliminary studies on the population of the legume pod-borer Maruca testulalis Geyer, using a pheromone trap at Mbita Point on the shores of Lake Victoria, showed that female moths produce a pheromone which attracts males. It was found that the peak catch of males occurred on the third night of female emergence, but after the fifth night the females were not attractive to males. This finding is regarded as significant in terms of studies on the population dynamics of M. testulalis.

Female Glossina morsitans morsitans maintained on rabbits previously immunized with whole tsetse body (WTB), engorged tsetse guts (ETG) or gravid tsetse uteri (GTU) for three successive generations showed no increase in mortality. However, a decrease in fecundity which varied with the tissue used as antigen and with the fly generation, was observed. During the three successive fly generations lasting about 4 months, the total decrease in fecundity was approximately 53, 59 and 70% for WTB, ETG and GTU respectively. The total increase in pupal mortality during the first two generations was approximately 7, 19 and 10% for WTB, ETG and GTU respectively, while the corresponding decreases in mean pupal weights were approximately 12, 8 and 11%. Flies fed on rabbits immunized with tsetse salivary glands (TSG), unfed tsetse guts (UTG) and protein extracted from gravid tsetse uteri (GTUP) showed a decrease in fecundity of 20, 26 and 31% respectively during the first fly generation, and a decrease in mean pupal weights of 6, 3 and 8%, while pupal mortalities increased by 38, 26 and 16% respectively.