Sperm are transferred from male to female tsetse, as in most insect species, within a spermatophore. The spermatophore of the tsetse species, Glossina morsitans morsitans Westwood (Diptera: Glossinidae), is highly organized, and can be visualized as a sac deposited in the uterus of the female tsetse. The wall of the spermatophore comprises two layers, whose components are strikingly similar to those of the secretions made by the male accessory reproductive glands. Dense aggregates of material, matrix filaments, and clusters of granules predominate in both. An ultrastructural study of these components is reported in this paper.

The relative efficacy of 25 acaricides, applied topically to the engorged adults of B. microplus was in the following order: chlorfenvinphos > tetrachlorvinphos > dimethoate > chlorpyrifos > fenitrothion > dicrotophos (LC50 = 0.000897−0.00244%) > naled > propoxur > crotoxyphos > pirimiphos ethyl > coumaphos > dioxathion (LC50 = 0.00425−0.00534%) > trichlorphon > lindane > carbaryl > allyxycarb > diazinon (LC50 = 0.00737−0.0149%) > promecarb > ethion > chlorpyriphos methyl > chlormebuform (LC50 = 0.021−0.0593%) > clenpyrin > chlordimeform > pirimiphos methyl > phosphamidon (LC50 = 0.1566™0.275%).

The order of toxicity is different from their relative efficacy against the larvae of the same population of the tick. Applied implications of the results are discussed.

In intertropical Africa, various haematophagous Diptera are considered responsible for the maintenance and spread of cases of cattle trypanosomiasis in regions where tsetse flies are absent. In comparing early observations with the results of two recent tsetse control campaigns, this paper raises the question of whether the role of machanical vectors is as important as that normally attributed to them, and stresses the insufficiency and impressive nature of available information on this important epidemiological problem, which requires much more intensive research.

Studies on the resting site preferences of the tsetse, Glossina palpalis gambiensis Vanderplank, were conducted in a gallery forest in the Northern Guinea Savanna in Mali. Tanglefoot was used to trap flies alighting to rest on the various site-types investigated. Five site-types were observed: boles, fallen logs, undergrowth (‘bush’), branches and tree canopies. Observations were made in the warm rainy, warm dry and hot dry seasons.

Distribution of resting flies on site-types was significantly heterogenous in each of the seasons. More than 80% of flies collected in each of the three seasons were found on fallen logs. Generally, there was no significant difference in numbers found on the top or side of fallen logs. Boles were the next best preferred site-type. Approximately 90% of flies on boles were collected below 1.0 m and none was found above 2.0 m. Few flies were collected from the undergrowth (bushes), tree canopies and branches. Similarities and differences between results obtained from the present study with those of other workers are discussed. The importance of the results in ground insecticide control operation against this species is noted.

Pirimiphos methyl when sprayed at dosages of 10 and 15 p.p.m., effectively protects dehusked maize in cribs for 3 months against incipient or cross infestation by stored product insects. Longer storage would however require a reapplication of the insecticide. At 5 p.p.m., pirimiphos methyl is not a protectant against insect infestation of maize stored beyond 1 month.

As insect numbers and grain damage increased, viability of infested maize decreased. Only when grain embryo is damaged or endosperm destroyed can insect infestation prevent grain germination.

The epidemiology of T. b. gambiense is reviewed in the light of recent findings, and potential animal reservoir hosts are listed. The discovery of distinct zymodemes in pigs with isozyme characteristics identical with stocks previously isolated only from man, and the human plasma resistant character (BIIT positive) of these stocks, is indicative of a zoonotic source of infection of man in some areas of West Africa. The likely epidemiological differences between savanna and forest foci are emphasised.

The focality of West African sleeping sickness is discussed in relation to the various hypotheses which have been propounded to explain this phenomenon. Recent observations which suggest Glossina can move longer distances on wind fields than hitherto supposed, and its possible implications as an explanation of some residual foci, is discussed. The possible impact of onchocerciasis on the distribution of foci is mentioned.

A sensillum trichodeum on tarsus I of Rhipicephalus appendiculatus displays a tonic impulse frequency at constant temperature but shows a phasic-tonic increased activity when temperature is lowered. Rising temperature has an inhibitory effect. Ultrastructural details show that it bears resemblance to a double-walled sensillum with spoke canals, and has dendrites of seven receptor cells. One of the cells responds to temperature changes. The function of the others is unknown.

Coprophagous beetles belonging to two genera, Onitis and Heliocopris, were collected and fed on proglotids and eggs of Taenia saginata. The beetles' faeces was collected after 24 hr onwards and examined for Taenia eggs. The flight range and behaviour of the beetles was investigated using cow rumen contents as bait for starved marked beetles. Results indicate that coprophagous beetles could play a role in dissemination of taeniasis.

Polyacrylamide gel disc electrophoresis of the salivary secretion from the tsetse, Glossina morsitans morsitans Westwood, showed 11 protein bands, four of which were characterized as glycoproteins. Sixteen amino acids and four sugars in the hydrolysates of saliva were identified. Thin layer chromatography showed five lipid classes and three phospholipids. The secretion is a clear, transparent, viscous fluid with a pH between 7.00 and 7.5. These findings are discussed in relation to the nutritional requirements of the metacyclic forms of trypanosomes that may be found in the salivary glands.

The biconical trap of Challier and Laveissièr was compared with Langridge's box screen (LBS) and Moloo's awning screen skirt (ASS) for relative efficiency in catching the tsetse species, Glossina pallidipes Austen, in two areas in Kenya. The dark blue biconical trap performed better than the ASS in one area, but both of them caught more males than females. In the other area, the sky blue version of the biconical gave higher yields than LBS and the white biconical. In both areas, the white biconical trap caught the highest proportion of old flies, while ASS caught the highest proportion of young flies. The biconical trap is preferable because it is collapsible, easy to handle and transport, and needs minimal manpower to operate, unlike the LBS and ASS.

The effect of six pyrethroids, NRDC 104 (resmethrin), NRDC 107 (bioresmethrin), NRDC 119 (cismethrin), NRDC 143 (permethrin), NRDC 156 and allethrin, against larvae and adults of the Egyptian mosquito Culex pipiens L. has been evaluated. Five strains were used, a field strain and DDT-susceptible, DDT-resistant, malathion-susceptible and malathion-resistant strains. Results obtained were also referred to a DDT highly susceptible strain of another mosquito Aedes aegypti (L.)

The toxicity curves showed that NRDC 156 proved to be the most effective compound tested, followed by NRDC 143, NRDC 119, NRDC 107 and NRDC 104, respectively, while allethrin was the least effective. Such a fact was highly pronounced either on the LC50 or on the LC95 basis.

As larvicides, data obtained proved that the DDT-susceptible strain was less susceptible to all the tested pyrethroids than the DDT-resistant strain by about 42.6-, 5.1-, 8.6-, 132-, 290.7- and 4.8-fold in the case of NRDC 104, 107, 199, 143, and 156 and allethrin, respectively. Tests also showed that there is no definite variation in susceptibility of both malathion-susceptible and malathion-resistant strains, except in the case of NRDC 143 and 156. Comparing tests against larvae of A. aegypti confirmed that the susceptibility to these pyrethroids was closely correlated with insect species and its strain, and cross-resistance might be developed among larvae of these species.

As adulticides, the pyrethroids used could be arranged in the following descending order according to their LC50 values: NRDC 156, NRDC 143, NRDC 104, allethrin, NRDC 107 and NRDC 119. The change in the trend of toxicity is possible due to the stage tested and the mode of action of these compounds on adult or larval stage.

There is increasing evidence that, under laboratory conditions, trypanosome populations which have the same genetic constitution by nature of the fact that they were derived from a cloned population but differ phenotypically in their expression of different surface variable antigens also differ in their infectivity and growth characteristics in certain environmental conditions. We have reviewed the evidence available for the existence of such a phenomenon in T. vivax and T. brucei variant populations and conclude that, in view of the fact that no physiological function has yet been attributed to the surface variable glycoprotein antigen, such differences most likely indicate concomitant expression of other genes controlling physiological processes which determine the parasite's ability to multiply in a given environment. The question of whether such a linkage between expression of a given surface variable antigen and expression of other physiological control genes is stable over extended periods of time or exists in all members of a trypanosome population displaying a given variable antigen is also raised but the experimental data at present available is too limited to allow any conclusions to be drawn.

The epidemiological importance of differences in transmissibility, infectivity, antigenicity, pathogenicity and drug sensitivity among species and strains of the African pathogenic trypanosomes is well known. These aspects of trypanosomiasis have been studied particularly intensively in the case of Trypanosoma brucei, but less attention has been given to T. congolense and T. vivax, the two most serious trypanosomal pathogens of domestic livestock. Our recent studies have included experiments involving the cyclical transmission by Glossina morsitans of stocks of T. congolense from locations in East and West Africa to rabbits, calves and sheep, and examinations of formation of local skin reactions and the antigenicity of the trypanosomes developing in these hosts. Differences have been observed in the occurrence of local skin reactions in different host species, and antigenic differences have been found between trypanosome stocks from different areas by serological tests and immunisation and challenge experiments. Differences in the serological responses of rabbits to different trypanosome stocks have also been observed during estimations of antibody levels using enzyme-linked immunosorbent assays.

Contact application of precocene 2 (6,7-dimethoxy-2,2-dimethylchromene) to inseminated adult female bed bugs inhibited egg maturation and affected egg viability. Third-stage nymphs exposed to 100μg/cm2 showed precocious maturation after the moult to the next stage. Nymphs exposed to lower concentrations of precocene exhibited teratism of the antennae, including the reduction of terminal sensillae. This was thought to be responsible for the bugs not assembling.

Reduction in the fecundity in adult bugs, and the morphogenetic and teratogenic activity in nymphs was circumstantially related to reduced levels of juvenile hormone, as a result of exposure to precocene.

Various traps have been used in East Africa to trap sandflies. These include: suction tubes, light traps and castor oil plates. Although limited success has been achieved through the use of these trapping methods, they were inefficient during the dry season. A new trap has been designed using castor oil-coated, clear plastic sheeting which has proved efficient in trapping sandflies indoors and outdoors even during the dry season.

Effects of age and hunger on the pattern of sound production in the tsetse, Glossina morsitans morsitans Westwood were determined. Although an afternoon peak was evident in young flies only on day 1 and virtually absent on all days in mature flies of both sexes, sound production in 12:12 LD basically seemed to follow a ‘U’-shaped pattern typical of other diel responses. Experiments under constant light (LL) and constant dark (DD) conditions did not indicate a clear circadian rhythm associated with sound production. Food deprivation led to a decrease in total daily sound production in contrast to other activities in G. morsitans morsitans.

Various species of sandflies were collected from outdoor natural resting sites from three districts in Kenya which are endemic for kala-azar (Machakos, West Pokot and Baringo). Their blood-meals were analysed to find out host preferences. Female fed-flies were dissected for parasitological investigation. Lizards from these areas were also trapped and blood and internal organs were examined and cultured for isolation of leishmania parasites. Only the lizards obtained from West Pokot and Baringo revealed leishmania parasites in cultures. Bloodmeal analysis showed that Phlebotomus anten-natus, P. bedfordi, P. schwetzi, P. africanus, P. martini, P. affinis and P. rodhaini fed on reptiles. Additionally, promastigotes were seen and isolated from these sandfly species. The disease incidence appears to be less in areas where leishmania parasites were encountered both in lizards and the sandflies in the same locality.

The control of Trypanosoma rhodesiense sleeping sickness by clinical methods is often complicated by the existence of animal reservoir hosts which greatly contribute to the persistence of the disease in many parts of East Africa. The control of sleeping sickness should, therefore, include control of the vector and elimination of the reservoir hosts. Another factor which is often ignored, when planning sleeping sickness control measures, is the influence of cultural practices of the resident human population on the epidemiology of the disease in any given location in East Africa. At Lower Kitete, northern Tanzania, trypanosomiasis due to T. rhodesiense is occupational in nature so that many of the individuals are infected in Lossitete Forest while engaged in various activities. The factors favouring infection within the area, and the role played by the cultural practices of the Masai around the area in bringing about the outbreak of an epidemic, are discussed. The importance of understanding the cultural practices and occupational tendencies of the Masai in Lower Kitete, where trypanosomiasis outbreaks have occurred in the last 10 years, is stressed. With such an understanding the management of trypanosomiasis at Lower Kitete may be successful.