Ecological surveys were carried out to assess the population characteristics and epidemiological importance of Glossina palpalis palpalis (Rob-Desv.), 1830 in the human trypanosomiasis focus of Vavoua in the forest zone of Ivory Coast. G. p. palpalis was widespread in all components of the ecosystem: forest, interstitial savannahs, coffee plantations, tracks and villages. Most flies were caught at the forest edge. Sex ratio and age composition of populations varied in relation to trapping sites. Open areas were dispersal places. Plantations provided resting, feeding and breeding sites giving rise to close man–fly contact. Here, teneral flies could become infected and later on transmit trypanosomes to plantation workers and their families. The role of man and domestic pigs together with that of fly behaviour and genetic factors in the transmission of the disease are discussed. Methods of tsetse control are suggested in the light of the findings.

Laboratory and field studies were made to investigate the toxicity, mode of action, and persistence of technical DDT and y BHC when applied to the cashew in Sri Lanka to control the mirid bug, Helopehis antonii Sign. The insecticides were tested at concentrations previously used in field trials.

Mirid nymphs were placed on the nuts and the rate of knockdown and mortality after exposure for a test period was recorded. These tests showed that BHC had a higher toxicity and acted more quickly than DDT. BHC had a powerful and transient fumigant action over DDT, which had no fumigant effect at all. Persistence was studied by treating cashew leaves and nuts growing under natural conditions and then testing the residual deposit at intervals.

It was concluded that BHC would be more effective than DDT when treating mature cashews because, in addition to its higher toxicity and quicker action, its fumigant action would compensate for incomplete coverage by low-volume spraying.

It has become increasingly noticeable that common features of many forest and forest/ savanna foci of West African human trypanosomiasis (WAT) are peri-domestic tsetse populations closely associated with domestic pigs. Recent evidence from various sources almost completely proves that, in at least some WAT foci, domestic pigs play an active role as reservoirs of Trypanosoma brucei gambiense. On the basis of this assumption, various aspects of Glossina palpalis and G. tachinoides local distribution and ecology, in relation to domestic pig and human populations, are discussed.

In those WAT foci where domestic pigs are kept, tsetse are widely distributed in forest islands, forest/plantations, and riverine forests, but major concentrations are in villages containing pigs. Close pig/fly relationships at the village level, involving peri-domestic feeding, breeding and resting behaviour on the part of flies, could be important factors in maintaining T.b. gambiense transmission in pig populations.

Endemic transmission of WAT to man could occur, either in villages where low pig densities dictate that a significant proportion of the fly population must also feed on man, or away from the village as a result of contact with infected flies which have strayed from a village transmission cycle.

The development of epidemic conditions could be explained, on the basis of changes in pig density and resultant changes in fly feeding behaviour. The sudden reduction of a pig population could result in an increased number of infected flies feeding on man, until such time as the fly population became stabilized on a reduced pig population (or on other hosts if pigs disappeared totally). During the period of increased feeding of flies on man, T.b. gambiense transmission could be intense.

Minor flare-up of WAT could occur if small numbers of infected pigs were introduced into a village area which had no previous history of pig husbandry. If a loose man/fly association persisted in such a village, endemic WAT could become a characteristic feature of that village.

Because of the fluidity of pig distribution and density, infected pigs could be instrumental in dispersing T.b. gambiense from village to village within a WAT focus and contribute to the persistent character of the focus. Pig movements involving much greater distances could also be important to the transfer of T.b. gambiense strains from one focus to another.

Larvae of the Caribbean fruit fly, Anastrepha suspensa Loew (Diptera: Tephritidae) parasitized by the wasp, Biosteres longicaudatus Ashmead (Hymenoptera: Braconidae), were topically treated with diflubenzuron (Dimilin®), a chitin synthesis inhibitor, at 100, 500 and 1000 ppm. Each dosage was initiated during the parasite's egg stage, each of four larval stages and the pupal stage (pharate pupa + pharate adult). Adults emerging from all immature stages treated with the two higher dosages were significantly (P < 0.05) fewer than the controls. Developmental stages, in decreasing order of susceptibility to diflubenzuron were: egg, first instar, pharate adult, pharate pupa and larval stages two to four. Abnormally developed ovipositors occurred in some adults which emerged from eggs, pharate pupa and pharate adults that were treated with the two higher concentrations. Such females were unable to successfully locate and parasitize hosts. Females with normal ovipositors which emerged from treated eggs and pharate adults were able to find and attack hosts but had significantly fewer eggs in their ovaries and oviposited less than the controls. The F1 eggs laid by these females developed normally and survived to adulthood with no apparent abnormalities.

The geographical distribution and the biology of the different species of tsetse fly are closely connected with the vegetation. Any modification in the vegetation cover may therefore change, in one way or another, the dynamics of tsetse populations and, consequently, influence the transmission of trypanosamiasis. Irrigation and rural development programmes which often drastically change the natural vegetation of vast areas will therefore result in major changes in the incidence, epidemiology and epizootiology of trypanosomiasis.

Only very limited studies have been carried out on this important problem and it is very difficult, if not impossible, to make a review of this subject as the data available are very fragmentary and often relate to specific situations.

The main purpose of this article is not only to review the data and information available at present, but also to identify and stress our lack of knowledge and the need for further research.

The problems created by establishment of irrigation and rural development programmes, industrial scale plantations, irrigated cultivations, livestock rearing centres are highlighted without neglecting the sociological and medical aspects of population transfers connected with these development programmes.

The conclusions attempt to identify the research which should be carried out in the field and propose some recommendations drawing attention to both the health services and to those responsible for planning and establishing irrigation and rural development programmes.

—The flesh fly, Sarcophaga ruficornis Fabr., was fed on thiotepa, and it was found that a 1% thiotepa solution produced complete sterility, which was due to the damage to the follicle cells and nurse cells. The passage of the female protein, ‘vitellogenin’, was blocked. Therefore, no trace of yolk granules was visible in the treated oocytes, but the oocytes and cytoplasm of the nurse cell contained vacuoles, and their nuclei were characterized by clumped chromatin contents.

The spread of human trypanosomiasis towards Central Africa from sources in the Congo at the beginning of the present century, has been linked to population changes and movements between the affected states.

The re-appearance of the disease in this part of Africa during the last 10 to 15 years raises again the question of how this disease is propagated. Although present day population movements are not so pronounced as those at the beginning of the century, these are significant population movements along major lines of communication (large rivers particularly). Of equal importance are disease foci which straddle national boundaries. Migrant populations (fishermen from Nigeria and displaced persons or refugees) also play important roles in the dispersal of the disease.

Even within certain foci, the mobility of rural populations helps to sustain the endemicity of the disease over large areas.

The risks of introducing or increasing trypanosomiasis must not be neglected when populating new areas and when developing agro-industrial complexes which require large labour forces.

A study was carried out during the wet and dry seasons, between October 1978 and May 1980 (altogether comprising four wet and three dry seasons), on the trypanosome infection rate in the tsetse species, Glossina pallidipes Austen, in rural situations in the Kiboko and Nkruman areas in Kenya. There were some sex and age differences with respect to trypanosome infection. Female tsetse showed higher infection rates, and old flies, both male and female, also showed relatively higher trypanosome infection rates. Infections with Trypanosoma vivax and T. congolense were different, both as regards to seasons and locality: the infection rate with the latter was higher in Kiboko than in Nkruman, and varied seasonally; while the infection rate with T. vivax did not vary significantly with seasons. The kind of traps used for sampling tsetse influenced the trypanosome infection rate indirectly by having a direct influence on the age structure of tsetse. The vertebrate hosts of tsetse in the two areas played an important role: the infection rates of tsetse with T. vivax and T. congolense were high in areas with a high density of bovids.

During the 1977/78 dry season an experiment was conducted in the Volta Noire source tributaries area of Upper Volta, to assess the feasibility of controlling human trypanosomiasis by reducing the vector, Glossina palpalis gambiensis, by a combination of techniques. The objective was to suppress the target tsetse population by chemical means and then to achieve a further reduction or eradication by the release of sterile males.

Sixteen kilometres of the fringing forest of the upper River Guénako were treated with the synthetic pyrethroid decamethrin (OMS-1998) applied from a helicopter as an aerosol at a dosage of 0.2 g/ha. Two applications at 14 days interval reduced the target G.p. gambiensis population by over 95% and caused important changes in the qualitative composition of both G.p. gambiensis and G. tachinoides populations. Subsequent over-flooding of the residual G.p. gambiensis population by sterile males was easily achieved.

The most efficient method of tsetse control remains the application of insecticides to that vegetation which provides the flies' resting sites. This paper briefly examines the observed toxic effects of insecticides on non-target organisms, which depends on the compound used, on its formulation and on the application technique. The importance is stressed of initiating research on toxicology and on the population dynamics of a few non-target species affected by insecticide applications. The problems of insecticide applications in game reserves are discussed. Following tsetse elimination, intensified efforts must be made to protect the fauna, within the framework of a general management programme for the whole of the reclaimed territory. The possibility of a rational exploitation of the natural fauna as a source of meat for human consumption is also mentioned.

In south-eastern Uganda the natural hosts of Glossina pallidipes, G. fuscipes fuscipes and G. brevipalpis appear to influence trypanosome infection rates in these vectors. The transmission index of these vectors also differs. Temperature is yet another factor affecting trypanosome infection rates in these tsetses. Other factors probably also form important components in the transmission cycle. In this region of Uganda and its contiguous lake shore area of Kenya there are extant foci of the infections, and man and his symbiotic livestock are exposed to a high challenge of trypanosomiases. Furthermore, in this high endemic/enzootic ecological zone of tropical Africa, the transmission of trypanosome infections to the adventitious hosts, via the tsetse vectors, depends upon a variety of complex interacting factors.

The Need for the correct identification of insect species cannot be overemphasized for without names scientific information in the biological literature cannot be meaningfully communicated. As noted by KIM (1975) ‘all biological research begins with accurate identification of the organisms to be studied and is based on general biological information about the organisms derived from the classification’. Further, in applied entomology, it is difficult to imagine an economic entomologist who may be expected to control a pest, the name of which (and hence its biology and distribution) he does not even know correctly. Although entomologists, indeed all biologists have recognized the need to use correct, up-to-date, valid scientific names, it is still fashionable for researchers, at least in the developing world, to work on their insect without worrying about its name which they hope will one day be somehow provided by somebody. Few biologists would consider publishing and fewer journals would be willing to accept articles without a scientific name of the investigated insect (Robinson, 1975).I trust that the members of the African Association of Insect Scientists are aware of the importance of taxonomic studies and the necessity of having an identification service. It is now well appreciated that there are far too few specialists working on the abundant insect species. As an example of the abundance of insect species the bug (Heteroptera) family Miridae has more species than there are birdsin the entire world.

Although organised insect taxonomic services have been in existence in Southern Africa for about 50 years these services are still inadequate and unsatisfactory. To improve this situation there is a need to make insect taxonomy more attractive to prospective entomologists by providing adequate funds, equipment and other facilities. There is also a need to create centralised well-funded and well-staffed institutions in which directed taxonomic studies can be carried out by linking posts with various collections at the same time leaving untreated groups to universities.