Orseolia oryzae, the rice gall midge, is a major pest of rice in many areas of tropical Asia and is becoming an important pest in Africa. A chronological review of the progress made in various national programmes on varietal resistance, sources of resistance and breeding for resistance is given. Many resistant varieties have been identified and have been utilized in breeding programmes to develop high yielding varieties with multiple resistance to the gall midge and other insect pests and diseases. Mechanisms and inheritance of resistance in rice varieties are discussed. Rice varieties resistant in various countries and sources of resistance used in breeding programmes are listed. Biotype variations in different countries and within the countries are revealed, and a preliminary classification of gall midge biotypes based on varietal reactions is proposed.

An intensive sampling programme for the estimation of the absolute size of the population of the cattle pest Stomoxys nigra Macquart in the sugarcane agro-ecosystem is proposed. Attention is focused on: (a) sampling at field level; and (b) sampling at national level. The best way of allocating the limited sampling resources between the various sub-divisions of the habitat to achieve efficient estimation is considered.

The numbers of the separate cohorts of the cocoa shield bug Bathycoelia thalassina which were observed up to hand-height on 50 cocoa trees in a Nigerian cocoa farm were recorded. The data were analysed for any patterns of aggregation. In the egg as well as 1st to 3rd nymphal instar stages, B. thalassina was highly aggregated on individual cocoa trees and the coefficients of aggregation ranged from 2.14 to 2.77. In the 4th and 5th nymphal instar and the adult stages distribution was random and analyses of data in units of 1, 2, 4, 8 and 16 cocoa trees did not reveal any patterns of aggregation.

More egg batches were laid on stem than on pods and the least number of batches was found on the leaves. There was no significant difference in the size of batches laid on different plant parts (P < 0.05) and cocoa pods did not influence the choice of oviposition sites by B. thalassina.

The implication of this distribution pattern was discussed, and a suggestion made for spot application of insecticides on the eggs or 1st instar nymphs as a method of control that would be both economical and of ecological advantage.

During sporadic outbreaks of S. exempta, population densities sometimes reach extremely high numbers. Monitoring at one such outbreak revealed that a considerable synchrony exists in the developmental processes of such populations, so that at times up to 97% of the population is represented by only one stage of development. Heavy pupal mortality with symptoms of a cytoplasmic virus infection was noted. Flight behaviour of emerging adults revealed observable differences in the flight activity of the moths. Although a great majority of the emerging moths flew away from the area, some stayed back. Eggs layed by the latter produced a second brood but, due to a more or less total depletion of the food source, this subsequent brood did not survive in any appreciable numbers and finally died out.

The onset of oviposition, incubation period, instar duration and polymorphism in the first progeny of Macrotermes michaeheni were investigated. Most incipient colonies have their first batch of eggs within the first week following establishment of the colonies. The incubation period for these eggs was 36.2 days. Three male and female larval instars, minor and major workers, and minor soldiers were found in the first progeny. Neither fourth instar larvae, which subsequently moult into major soldiers, nor nymphs, which develop into reproductives, were detected.

The duration of each larval instar was determined. The longest duration was that of third instar larvae developing into both minor and major workers. The first neuter terminal castes which appeared in the colonies were minor workers, followed by major workers and, soon after, by minor soldiers in the majority of cases.

1. Under laboratory conditions (25 to 27°C), female Cydia ptychora (Meyrick) laid an average of 44 eggs. 2. The egg incubation period was 5 days, while the larval developmental period lasted 7 to 10 days, and the pupal period 12 days. Thus, the total developmental period (egg to adult) lasted 24 to 27 days. The adult longevity averaged 10 days (13 to 15 days). 3. Descriptions of the different life stages and setal maps of the different larval instars are provided.

Although mating is a necessary prerequisite for the induction of ovulation in the tsetse fly, Glossina morsitans morsitans, neither the accessory gland substance from the male nor any testicular component is responsible for causing ovulation. Experimental evidence suggest that two neural factors, one originating from the uterus during mating act as an afferent stimulus, and the other originating from the ovary during oocyte maturation regulate a cerebral hormonal factor which controls the event of ovulation. It is probable that one successful copulation removes an inhibition for the release of an ovulation stimulating hormone from the neurohemal organ into the circulation. The rate of synthesis and/or transport of the hormone from the neurosecretory cells to the neurohemal organ is probably regulated by the rate of oocyte development.

The pattern of singing activity of Glossina morsitans morsitans was monitored in LD 12: 12. Both males and females showed a clear “U”-shaped diurnal pattern of singing activity typical of other responses in tsetse flies. The morning peak comprised more activity than the evening peak. The significance of sound production and the possible endogenous control are discussed.

In the course of the in vitro cultivation of Trypanosoma brucei as midgut forms, immature metatrypomastigotes, and metacyclic forms, a phenomenon was observed that suggested possible existence of sexual forms consisting of two parasites of unequal size which were seen to come close to each other with their posterior ends apposed. The smaller parasite which was more active than the larger one travelled along the side of the latter so that its posterior end came to lie in the region of the kinetoplast of the larger one. At the latter site, the smaller parasite displayed vigorous twisting movements and later came to lie parallel to its partner. Electron-microscopic examination of the parasites revealed that the points of contact were the kinetoplast and the flagellar pocket. These observations point to the possible existence of sexual forms, and the transfer of genetic material in the 3 types of T. brucei cultured from the vector, G. m. morsitans.

The performance of two laboratory colonies of Glossina pallidipes Austen originating from two areas in Kenya, Nkruman in the Rift Valley and Mwalewa forest in the coastal area, are described and compared. Two attempts to rear flies from Nkruman failed. Flies from Mwalewa were maintained with variable success for four years. Difficulties in rearing flies from Mwalewa could be explained by irregularities in the conditions of the breeding room, in contrast to failures in rearing flies from Nkruman. Life budgets were made to evaluate the performances of the colonies. In both Nkruman colonies the highest mortality factor was ‘loss due to non-production’. In the Mwalewa colony the highest mortality was ‘loss due to low production’. The key mortality factors were ‘loss due to low production’ (Nkruman colony A), and ‘premating mortality’ (Nkruman colony B, and Mwalewa colony). Factors which possibly contribute to the difficulties in rearing G. pallidipes are discussed. Flies from Nkruman and Mwalewa differed from each other in copulation time, pupal weight, age at which the first larva is produced, and duration of interlarval periods. The results of this study support the assumption of the existance of population diversity in this species.

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.

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.

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.

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.

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.