The possibilities of migrations in the West African species of Dysdercus are discussed and a hypothesis of long-range migrations associated with the Inter-Tropioal Convergence Zone and its wind systems is proposed. Catches of adult Dysdercus in four light-traps distributed from south to north of the Ivory Coast showed that the phenology of assumed migratory activity in D. voelkeri Schmidt differs with latitude and may be correlated with particular types of weather; stainer migrations taking place during the warm, wet and sunny part of the year. The whole life cycle of the insects as well as their flight activity occur under these climatic conditions, prevailing in a belt of 600–900 km width, situated immediately to the south of the Inter-Tropical Front. Colonisation of newly available habitats is thus only possible when climatic factors allow: (i), migratory flight activity and (ii), survival in the colonised area. A close examination of the timing of both migrations in the two main species, D. voelkeri and D. melanoderes Karsch, and of annual movements of the I.T.F. leads to the only logical hypothesis that the transportation of migrating insects is effected by atmospheric convergence, prevailing wind currents and air mass displacements.

A critical review is presented of the many and varied procedures for sampling adult mosquitoes. All sampling methods are subject to bias, but human-bait collections are probably the most reliable single method for detecting and monitoring populations of anthropophilic species. The estimation of realistic man-biting rates, however, remains difficult. The recent advances in computer technology have generated considerable interest in population modelling, with the aim of getting a better insight into the complexities of population dynamics, mosquito control and disease transmission. Although such approaches may be informative, it is stressed that models should be based on meaningful values of the critical parameters and that these are best obtained from field populations. The difficulties of interpreting mosquito collections in both attractant traps, such as animal-baited traps, carbon-dioxide-baited traps and light-traps, and in non-attractant ones, such as Malaise traps, sticky traps, ramp traps, rotary traps, suction traps and vehicle-mounted traps, are described. Suction traps probably provide the least biased catches of aerial populations of mosquitoes, but, if populations as a whole are to be considered, then resting adults also must be adequately sampled, and this may prove difficult. It is emphasised that different trapping techniques usually sample different components of a population, and that the choice of sampling methods depends much on the type and quality of information required. The limitations of using mark-recapture techniques to study adult dispersal and obtain absolute population estimates are discussed, together with the advantages and disadvantages of applying simple and more complex mathematical procedures for analysing recapture data.

Light-traps were used to sample populations of C. comutus De Meillon, C. pallidipennis G, I. & M. and C. schultzei (End.) gp. at sites at Embakasi, Kiboko and Makindu between 1971 and 1975. The samples were graded into age-groups by the degree of abdominal pigmentation, estimates of calendar ageing were made, and the seasonal variation in age-structure of the populations was recorded. Survival rates were calculated on the basis of a graphical model of the continually overlapping generations, and the survival rate of 0·8 was found typical. This rate is considered sufficiently high for C. cornutus, C. pallidipennis and C. schultzei gp. to act as vectors of bluetongue virus disease of sheep and/or ephemeral fever virus disease of cattle.

Light-traps were used to collect adult Culicoides from 61 sites throughout Kenya and to sample long-term population fluctuations at six sites. Activity patterns were recorded with a suction trap and larval habitats were sampled with laboratory emergence traps. Culicoides cornutus De Medllon, C. milnei Aust., C. pallidipennis C, I. & M., C. schultzei (End.) gp. and C. zuluensis De Meillon were found widespread and also concentrated at livestock pens. Their seasonal population fluctuations did not correlate clearly with rainfall but all these species persist throughout the year. The activity of C. pallidipennis and C. schultzei gp. extends over the whole night and is inhibited by winds in excess of 3 m/s and stimulated by high temperatures and relative humidity. Larval habitats were mainly in mud mixed with detritus or dung; larvae of C. pallidipennis and C. schultzei gp. were both found in swamp mud but not in dung pats. The significance of these findings is discussed in relation to the epidemiology of bluetongue virus disease of sheep and ephemeral fever virus disease of cattle.

The technique of applying persistent insecticides (largely dieldrin or endosulfan) from the air by helicopter against Glossina spp. in northern Nigeria is described. In the Guinea savanna vegetation zone, a high degree of discrimination was practised. Where the riverine species G. tachinoides Westw. and G. palpalis palpalis (R.-D.) only were present, spraying was confined to the fringing forest vegetation along drainage lines and in flood plains. Where the savanna species G. morsitans submorsitans Newst. was also present, Isoberlinia woodlands were also sprayed in swaths along the outside edges and penetrating swaths at maximum intervals of 200 m; the denser vegetation encircling the many flat-topped hills was also sprayed, as well as the main tracks and cattle routes. The more undifferentiated woodlands in the southern Guinea savanna zone were sprayed as a grid with swaths at intervals of 150 to 200 m. The degree of discrimination varied according to the fly species and density of the vegetation; usually 5 to 16% of the totally infested area was actually sprayed. So far, approximately 10 000 km2 have been reclaimed from tsetse by this technique. The degree of reinvasion encountered per annum was approximately 25% of each project area. All reinfested areas have been successfully resprayed. Costs averaged approximately 18 Naira/ha actually sprayed or 2 Naira/ha of reclaimed area in the northern Guinea savanna zone. In the southern Guinea savanna zone, the reclaimed area averaged 3 Naira/ha. The ultra-low-volume spraying technique was introduced in 1972, and this has gradually replaced the conventional spraying technique using emulsion concentrates and booms and nozzles. The ULVA-Bals single-disc atomisers were modified and improved so that droplet sizes within a range of 70 to 200 μm volume median diameter can be produced as required. Many insecticides have been tested in the laboratory, preliminary tests on permethrin indicate; that it may prove to be a useful alternative to dieldrin and endosulfan.

Field and laboratory studies at Ibadan, Nigeria, showed that the young nymphs of Zonocerus variegatus (L.) normally reject cassava after biting it and die if they are confined on growing leaves. Later instars will eat cassava, especially when deprived of food for some time, but the adults progressively lose weight when restricted to feeding on growing cassava. On cut cassava, on the other hand, extensive feeding occurs and normal growth is maintained. The change from unpalatability to acceptability occurs within about an hour of cutting and is apparently associated with wilting. Cassava produces latex, but this was not distasteful to Zonocerus. The readiness to feed on growing cassava was associated with low levels of hydrogen cyanide production by the leaves; wilted leaves still produced hydrogen cyanide, but at a lower rate than turgid, growing leaves. In the area around Ibadan, Zonocerus regularly defoliates cassava in the latter part of the dry season, probably because a shortage of attractive foods forces the insect to eat cassava.

Movements of individual fourth instar Coccinella septempunctata L. larvae on pot-grown broad bean plants in England were recorded continually to assess plant recognition and the effects of prey capture. Prey capture was also studied in a 25X25 cm artificial arena. Approximately 80% of the total distance moved by larvae on plants was along leaf edges and mid-veins. Typical search speeds were 0−38−0−51 cm s−1. An average of only 3−2% of larval search time on plants was spent on leaf laminae on which movement was considerably slower, about 0−15 cm s−1. Discovery of Acyrthosiphon pisum (Harris) nymphs on plants induced intensive re-searching of the general area of discovery for periods of up to 12 min whereas in the arena the intensive search following prey capture lasted only up to 72 s and was much more localised. Examination of larval search times on plants revealed that 64% and 36% of maximum search times were recorded for the first and for the second or third searches, respectively, in a sequence of searches of the same plant. Only after prey capture was a fourth or subsequent search the longest. Plants previously searched unsuccessfully were recognised by detection of a chemical marker, specific for each individual, secreted via the anal disc during searching. Since C. septempunctata larvae are unable to detect aphids by sight or smell, recognition of areas previously searched unsuccessfully minimises wasteful energy expenditure.

The genus Chaetanaphothrips Priesner, comprising seven species and including pests of bananas, tea and orchids, is revised, and a key is provided for their identification. The host preferences and distribution of each species are discussed briefly.

Australoglypta latrobei gen. et sp.n., an ichneumonid parasitic on the larvae of the tortricid Epiphyas postvittana (Wlk.) in Australia, is described and compared with related genera. The mating and oviposition behaviour of the ichneumonid is noted, and its abundance over 13 generations of E. postvittana between 1972 and 1976 was investigated. A delayed inverse (density-dependent) relationship was found to exist between host and parasite. Possible beneficial effects of this parasite are discussed.

Males of Diparopsis castanea Hmps. were caught in a water trap baited with sex pheromone sited 2·0 m above ground level in a cotton field in the Lower Shire Valley, Malawi. Analysis of catches for 21 nights between 8.iii.75 and 3.vi.75 showed that optimal catches of males occurred at wind speeds of 1·0−2·5 m s−1. Wind speeds in excess of 3–4 m s−1 depressed activity. Regression analysis revealed an optimal relative humidity for flight of 60−70%. Inclusion of humidity in a multiple regression analysis with wind speed and temperature failed to improve significantly the relationship with catch provided by a model that considered wind speed and temperature only. No simple relationship existed between temperature and moth abundance, and wind speed clearly exerted the greatest independent effect on catch. Male Diparopsis nevertheless exhibited a temperature-related pheromone responsiveness, with peak catches occurring earlier in scotophase during periods of cool weather. Analysis of data gathered during the 1973 and 1974 seasons indicated a slight, but significant, positive correlation between night rainfall and moth catch. However, none of the various independent and joint relationships established between moth catch and climatic factors could be reliably used for forcasting moth abundance.