Sorghum, maize and cowpea serve as staple food for people in Africa and are grown mostly by small-scale farmers. A major constraint on the production of these crops is attack by insect pests among which crop borers are most important, causing 30–80% yield losses. Use of pesticides to control these pests is hazardous and not feasible for the farmers. Alternative strategies for the integrated pest management (IPM) are being developed at the International Centre of Insect Physiology and Ecology (ICIPE) and include the following components: (1) Intercropping and other cultural practices, (2) Plant resistance to insect pests, and (3) Biological control. These IPM components have now been developed to a stage where they can be taken for on-farm trials under farmers' management for subsequent use by them. But, adoption and diffusion of agricultural innovations requires a prior knowledge of the farming systems and the socio-economic circumstances in which the target farmers operate, and their bearing on the use of innovations. Information on these aspects has therefore been obtained through a survey of farming households in Kendu Bay and Oyugis Divisions in western Kenya during April—August 1986. The survey was conducted jointly with UNECA and Ministry of Agriculture, Kenya, under a project funded by the Royal Government of Belgium.

The survey involved interview with 150 farmers, (75 in each Division. In Kendu Bay 27 were men and 48 women whereas in Oyugis 40 were men and 35 women.) and was based on a questionnaire which comprised six sections. Five sections covered the farmers' background, farming practices, pest problems and their control, socio-economic conditions, and accessibility/willingness of the farmers to participate in the project. The last section included field observations on the insect pests of sorghum, maize and cowpea.

On the basis of the information obtained on above-mentioned aspects, criteria were defined and assigned appropriate weigh tage for selecting 25 farmers in each Division for on-farm trials. The selected farmers included 12 men and 13 women in Kendu Bay while in Oyugis 13 men and 12 women were selected.

The measures that need to be taken to counter these limitations and thereby assist the farmers in increasing food production have been recommended.

Partial sterility induced by gamma irradiation of Ephestia cautella adult males was studied in five laboratory strains (A,B,C,D and E) which exhibit conspicuous genetic variation in the adult forewing pigmentation. Four of these strains had been reared in the laboratory for more than 80 generations, while the fifth strain has been reared for only 10 generations. When males irradiated with 0.2 kGy were crossed with untreated females, the per cent egg hatch was reduced significantly as compared to the unirradiated control crosses. Strain C showed the highest reduction in the per cent egg hatch followed by a gradual decrease in radiation sensitivity in strains A,E,D and B, respectively. Fecundity and mating frequency appeared not to be affected but the sex ratios were clearly distorted (about two males to one female) in all strains. F1 progeny of all strains were either sterile when mated together (per cent egg hatch = 0.0%), but semi sterile when F1 males were mated to normal females (per cent egg hatch = 0.03–3.95 %). Low fertility was observed when F1 females were mated with normal males (per cent egg hatch = 1.30–15.04%). The cytogenetical investigations showed spermatogenesis to proceed normally in the F1 males, whose fathers had been irradiated (0.2 kGy). However, the primary spermatocyte cells carried multiple chromosomal translocations which were the main cause of the sterility in the F1 males.

Adult (2–20 hr old) viviparous Aphis craccivora were treated with 0.5 to 4.0 μg of precocene II. Treatment led to dose-related reduction in the progeny number, survival and life span of the aphid, but wing development was not affected. With 2.0 μg/aphid or more of precocene II, all surviving offsprings shared precocious metamorphosis, but even with 0.5 μg/aphid, about 20% progeny showed such metamorphosis with 1.0 and 1.5 μg/aphid. Early nymphs tend to undergo precocious metamorphosis earlier, in the second moult.

The development of phase phenism in L. erysimi involved function related changes in the activity of hydrolytic enzymes. The esterase activity decreased from first to third instar and then increased in the fourth instar and adults. The decrease in the third and the increase from fourth instar up to adults was more in alatae than apterae. The acid phosphatase activity was maximum in second instar. It decreased in the third and then increased again in the fourth instar and adults. The increase was more in alatae than in apterae. The alkaline phosphatase showed a similar trend but was in contrast to acid phosphatase and showed low activity in alatae as compared to apterae.

A new eye colour mutant, “Orange eye (Or.)” is described for Ephestia cautella, Baghdad strain. This mutation is inherited as an autosomal recessive mutant. Fecundity of the orange-eyed strain is significantly reduced while its viability is not affected.

Laboratory studies were conducted on the role of flood on egg development, survival and hatchling weight in the solitary phase of Locusta migratoria migratorioides (Reiche and Fairmaire). Egg development is retarded by flood, particularly if the eggs develop for a long period in ordinary moist soil prior to flooding. Floods are also detrimental to egg survival; eggs that are flooded immediately after oviposition and those flooded when they are about to hatch are particularly susceptible. Egg age at flooding is a major determining factor of hatchling weight; heavier hatchlings are produced if eggs develop in ordinary moist soil for longer, rather than shorter, period before being flooded. Length of flooding period has no apparent effect on hatchling weight.

The distribution pattern and larval behaviour of the major flower and pod borer Lampides boeticus on vegetable lablab were studied in Bangalore, India. The distribution of eggs and bored flower buds were found to be contagious. Most of the flower buds with pin hole damage had small larva (first and second instar) inside them. Flower buds with medium damage had medium larva (third instar). The flower buds and pods with large damage very rarely harboured larva. The medium and large larvae migrated and caused damage to flower buds and pods. Use of larval behaviour in developing a suitable pest management programme is indicated.

The survival rates of humus-feeding Cubitermes testaceus (Williams) workers were determined in relation to soil organic matter content. Field collected termites survived for 15.5 days when fed on soil with the highest content of organic matter (5.1%) and for 8.1 days when fed on soil with the lowest content of organic matter (3.2%). Possible reasons for termite workers' survival are discussed.

The predacious mite, Hypoaspis vacua (Michael) successfully developed from larva to adult stage when fed on eggs of housefly, Musca domestica (L.) and nymphs of acarid mite, Rhizoglyphus echinopus (Fum. & Rob.) in the laboratory. The duration of the immature stages and of the adult stage were determined. Food type greatly affected female fecundity and feeding capacity. Immature stages of H. vacua consumed in total an average of 13.6 eggs of M. domestica and 33.0 nymphs of R. echinopus, whereas each day throughout her life, the adult female consumed an average of 4.1 eggs of M. domestica and 13.23 nymphs of R. echinopus. Eggs of housefly were the most suitable diet, as it prolonged adult longevity (76.8 days) and increased female fecundity (1.3 eggs/female/day).

In field conditions in South Australia hatching of eggs of Ectropis excursaria showed a morning and an afternoon peak. In the laboratory, hatching coincided with “lights-on” stimulus at 20°C, 10:14 and 12:12 L:D. Increase or decrease of temperature by 5°C shifted the start of hatching to late scotophase while increasing photoperiod shifted a substantial proportion of hatching to later in photophase. Survival of first instars was linearly related to saturation-deficit of the atmosphere.

Flight activity in strain 16cSS of Anopheles gambiae (sensu stricto) has been investigated using an acoustic actograph. The peak activity was concentrated within the first hour after light off. After recording their activity, individual mosquitoes were examined for their chromosome inversion karyotype. No significant relationship was found of any of the karyotypes to total activity over the 2 hr after light off or the time at which 50% of their activity had been completed.

The results are discussed in relation to the possible widespread introduction of mosquito bednets and the possible selection of mosquitoes biting abnormally early before people go to bed.

—Life table studies of American bollworm Heliothis armigera Hubner on four species of cotton revealed that maximum mortality in the population occurred early in the life cycle. Predation and dispersal accounted for maximum mortality of early instars, whereas migration and unknown reasons accounted for maximum mortality of late instars. Considering the life tables on four varieties of cotton, the loss of population during the first instar was significantly high in K8 and TKHe 44 whereas in Suvin and MCU 9 the loss was less.

Examination of Giemsa stained smears made from the peripheral blood, liver and spleen of hand-caught lizards from West Pokot area showed the presence of seven out of the nine Plasmodium species of lizards which have been previously described in Africa. These species are redescribed using a set of biological characters and procedure which enabled a large quantity of each stage of any species to be studied, measured and compared. The utilization of these characters and procedure was a reaction to the multiple infections in individual lizards and a wide host range of each species among lizard species. The adoption of the criteria is recommended for future taxonomie work on lizard Plasmodia in Africa.

A key which brings together all the previously described species of lizard Plasmodia and the new species encountered in the present investigation is presented. The key is simplified so that it can be of use to epidemiologists and pathologists who may work on saurian malaria in Africa.

In experiments to find the yield loss in soyabean due to the leaf miner, Aproaerema modicella (Deventer) and estimate the economic injury level (EIL), plants were infested at 30 and 45 days after sowing (DAS) with a fixed number of laboratory reared second instar larvae.

Grain yield was not reduced by one larva per plant at both 30 and 45 DAS, but the yield reduction which ranged from 2.7 to 6.1% was significant with two larvae per plant at both the ages. With an increase in larval population, there was a corresponding decrease in yield to the extent of 40% and 66% with 10 larvae/plant at 30 and 45 DAS respectively.

The regression of yield of leaf miner infestation indicated that yield was reduced by 0.463 and 0.716 g per plant for every larva per plant at 30 and 45 DAS respectively. Yield loss was greater in plants infested at 45 DAS than at 30 DAS with all populations tested.

The estimated economic injury level for A. modicella is 0.6 larva/plant at 30 DAS, and 0.2 larva/plant at 45 DAS. The suggested economic threshold level in soyabean of 85–90 days duration is 0.5 larva/plant (1 larva/2 plants) at 30 DAS and 0.2 larva/plant (1 larva/5 plants) at 45 DAS.

Establishment and maintenance of a laboratory colony of Phlebotomus argentines are described which presently is in the nineteenth generation. Larvae were reared in modified plastic vials and were fed with a newly prepared food. Emerged flies were kept in adult holding cages at 50–90% r.h. and 25–26°C and provided with 30% sucrose solution. The average development time (egg to adult) of each generation in the laboratory was about 32 days at 28–31°C. Adult females were fed blood on hamsters, humans and white mice. Observations were made on mating behaviour, host preference, oviposition, effect of temperature, etc.

Some aspects of the reproductive behaviour of the tossa jute defoliator, Acraea terpsicore (L.), were studied. The insect mated only once. A horny material was deposited on the female's genital aperture after mating. Mating began on the day of emergence and lasted for 7 days on 10% sucrose solution. Maximum number of matings was on the third day after emergence. Within the day, over 95% of matings was between 0600 and 1800 hr with a peak between 1200 and 1800 hr. Eggs were also laid mainly between 0600 and 1800 hr during the day with a peak between 1500 and 1800 hr. Oviposition which started on the day of emergence lasted for 7 days on 10% sucrose with a peak on the second day. The presence of the male, after mating had occurred, did not significantly affect the number of eggs laid. Adults emerged between 0600 and 1800 hr but mostly before mid-day. Peak emergence for males occurred earlier than that for females. Behavioural activities in courtship, mating, oviposition, and adult emergence, are described.