The variations of moisture in the leaf litter of Eucalyptus tally with the fluctuations in the populations of microarthropods of the litter. The acarines and collembolans are the most numerous. We note at the end of the rains a spectacular rise in the rate of increase of psocids in this litter, as well as an obvious drop in the population of entomobryomorph collembolans (specific prey of Smithistruma) which have begun to penetrate the soil looking for moisture. An analysis of the sampling of prey carried back to the nest by foraging workers shows that, whatever the season, the capture of entomobryomorphs is the highest. In the rainy season, the majority of the prey are these entomobryomorphs; while, with the coming of the dry season, the rate falls to 31 then 21%. On the other hand, the foraging workers catch psocids, Acarina, and termite larvae by way of compensation.

The population of green spider mite Mononychellus tanajoa (Bondar) was monitored on cassava for 52 weeks (mid October 1979 to mid October 1980) at Moor Plantation, Ibadan, Nigeria. Mite population was found to be high in the dry season (80.1 ± 57.7 per leaf) and low in the wet season (15.2 ± 13.5). There was a linear relationship between mite population and the weather factors investigated. The relationship was positive in the cases of temperature and radiation, and negative in those of rainfall and humidity. The high mite population in the dry season was attributed to the high temperature (27.9 ± 1.26°C) and radiation (39.1 ± 7.86) conditions which favoured development of the different stages in the life cycle of the mite. The low population in the wet season was attributed to the adverse effects of high rainfall (56.31 ± 33.14 mm) and humidity (87.29 ± 2.36%) on the mites. Seasonal fluctuations in mite population was attributed to the physiological condition of the host plant.

Changes in the activities of general esterase, L-alanine:2-oxoglutarate aminotransferase (GPT), L-aspartate:2-oxoglutarate aminotransferase (GOT), acid and alkaline phosphatase after allatectomy, brain-cauterization and juvenoid treatment have been studied. It has been shown that allatectomy reduces the GPT, GOT, general esterase and acid phosphatase activity in all tissues from both sexes and alkaline phosphatase activity in all the cases excepting the testis. Treatment with juvenoid in allatectomized insects reverses the effects of allatectomy. Both allatectomy and brain-cauterization cause the drastic decrease of all the enzymes in both sexes. The physiological significance of these findings has been discussed in this paper.

Topical application of the juvenile hormone mimic 1™75 to pregnant Glossina morsitans 15 or 20 days after emergence resulted in a significant increase in abortions of eggs and larvae of all developmental stages. Small doses (0.25 ng per fly) were sufficient to elicit a response which was more pronounced if application occurred 20 days after emergence. Flies fed once on rabbit ears, which had been treated with 5 ng of the mimic per ear, resulted in abortions and the effect persisted for up to 40 days. The hormone mimic did not induce abortions in isolated pregnant uteri kept in organ cultures for up to 7 days.

Surveys on the stem borer complex of rice were initiated at Mbita Point Field Station during 1980–1981. Stem borers collected and identified so far included Maliarpha separatella Rag; Diopsis thoracica West; Sesamia calamistis Hmps., and Chilo partellus Wlk. Among these four species, M. separatella was the most abundant and showed highest infestation during the reproductive and ripening phases of the rice crop. D. thoracica was found to cause greatest damage on the crop during the crop's tillering phase. It is suggested that there may be differences in Maliarpha infestation due to rice varieties.

Maliarpha separatella (Rag) was found to infest the rice crop for the greater part of the crop's growth cycle. There was an extended peak of larval activity, and the build up of the larval population was correlated with stand establishment and stem development. The intensity of both tiller infestation and internode tunnelling was found to increase with the crop maturity. Some aspects of control measures of the pest as related to the insect-pest/host-plant relationship are discussed.

Between 1979 and 1980, the incidence, breeding sites and infection rates of Simulium damnosum with Onchocerca volvulus were investigated on rivers Amire-u-Kiriki and Katsina Ala in a local government area of the Benue State of Nigeria, in West Africa. Several breeding sites were located along the rivers. All the Simulium caught were identified as S. damnosum, and a greater number was encountered during the rainy than the dry season. The numbers of infected and infective S. damnosum were ascertained through the dissection of the caught flies; the number of bites per day as well as the number of infective bites per person per day were estimated for each zone of investigation. It was concluded that the areas of investigation are highly endemic for human onchocerciasis, and the consequences of this on the people living in the area are discussed.

The pest complex of sunflower and its relative abundance and economic importance are discussed. A total of 80 insect species were collected—five of these were recorded on roots, 51 on stems and leaves and 29 on floral parts and developing seed. The major pests of sunflower commonly encountered in all the localities studied were Agrotis segetum Schiff, Agrotis ypsilon Hfn, Plusia orichalcea F., Nezara viridula L. and Heliothis armigera HB.

The trends in flowering, podding and seed yield of four cowpea varieties planted at different times of the growing season in 1975 and 1976, were studied along with the associated pest activity. Flowering, podding and seed yield were found to decrease over the season from April to September irrespective of whether the crop was protected against insect pests or not. However, there seemed to be two peak periods of pest activity—April to July and October to December—when severe damage to the crop occurred in unprotected plots. Planting in June or July usually led to an escape from several major pests even though the cool night temperatures and incidence of overcasts at that period seem to preclude optimal reproductive performance of the crop.

The pattern of insect pest succession on the crop over the season is discussed and it is suggested that for small farm holders in Southern Nigeria, who are unlikely to apply insecticides, planting in June is advisable.