The effect of exposing 1, 3 and 5 days old pupae to 10°C for periods of 7, 14, 21 and 28 days on the emergence, pre-oviposition and fecundity of Cryptolaemus montrouzieri Mulsant was studied. The emergence was delayed significantly when 1 and 3 days old pupae were subjected to 10°C for 28 days when compared to 5 days old pupae. The initiation of oviposition was delayed with the prolongation of holding time. The fecundity of females emerging from 5 days old pupae subjected to 10°C for 21 days was found to be significantly higher than in any other treatment.

This paper combines some of the results from three studies that explain the system by which the gut of Phlebotomus papatasi is maintained bacteria free. This system includes an antibacterial factor in the crop (diverticulum) and feeding behaviour which determines selective routing of meals. When feeding by piercing animal skin or plant tissue, in a ‘blood feeding’ mode, the uncontaminated meals of both sources enter the midgut directly. Free-solution sugar-meals which may contain contaminants, enter the crop where they mix with the antibacterial agent. Feeding on plants is also described.

The effect of solar radiation, rainfall and cannibalism on the disappearance of eggs and larvae of the cereal stemborer Chilo partellus (Swinhoe) were studied. Disappearance and nonviability of egg batches was higher on plants exposed to solar radiation than on shaded plants. Significantly fewer small larvae were recovered from plants exposed to rainfall than from shielded plants. Cannibalism among larvae of the same size was not common except at high larval densities. Contrary to the common belief that disappearance is the result of predation, these studies show that solar radiation and rainfall might also play an important role in the disappearance of stemborer eggs and small larvae.

The effect of 10, 20, 30, 40, and 50 adult Sitophilus zeamais on the quality of 1 kg lots of white maize maintained at 25−30°C and 65−85% r.h. was observed. Per cent moisture, oil, Free Fatty Acid (FFA) content and germination were determined at 2-week intervals for 10 weeks.

Moisture content of infested maize ranged from 11.51 to 12.92%. There was a significant correlation between moisture content and degree of infestation (r = 0.88; P < 0.05; Y = 11.908 + 0.006 x). The range of oil content of infested maize was 4.83−5.75%. There was a significant correlation between oil content and degree of infestation (r = −0.097; P < 0.05; Y = 5.08 −0.0076 x). The free fatty acid (FFA) of infested maize was 5.82−6.86%. The heterogeneity at various infestation levels was significant (F = 81.38; d.f. = 5; P < 0.001). There was an increase in FFA, with increasing infestations, although the correlation was not significant.

The germination of maize, 10 days after planting, at various infestation levels was 43.0−97.5%. There was a decrease in germination, as level of infestation increased. The heterogeneity in germination at various infestation levels was significant (F = 19.21; d.f. = 5; P < 0.001). Possible reasons for the results obtained, are presented.

Some properties of the gut amylase of Sophrorhinus insperatus Faust have been studied. The enzyme has maximum activity at pH 5.0 and 45°C. It is activated by C−, Ca2+ and Cd2+ tons and inhibited by Cu2+ and Hg2+ lons. Low Michaelis constants of 0.26 mg/ml and 032 mg/ml were obtained for the larva and adult gut amylases. Enzymatic activity was found to be consistently higher in the larva than in adult stage, probably suggesting the larval stage as the most destructive stage. Extracts of Cola nitida (Vent) Schott and Endlicher and C. acuminata (Pal de Beauv) Schott and Endlicher, inhibited amylase activity in vitro at varying magnitudes. The higher level of inhibitors in C. acuminata is an index of its low susceptibility to weevil attack both on the field and at storage.

Cotesia sesamiae (Cameron) (Hymenoptera: Braconidae) is an indigenous, gregarious, larval endo/parasitoid which is widely distributed in Africa and attacks mid- to late instars of stemborers. There is renewed interest in using Co. sesamiae for biological control to reduce the problems caused by stemborers. However, Wolbachia sp., a bacterial symbiont of some populations of Co. sesamiae, poses some threat to the successful use of the parasitoid for stemborer control. This bacterium's common effect is cytoplasmic incompatibility between infected males and uninfected females. Polymerase chain reaction (PCR) tests were carried out on parasitoid samples collected from 5 locations in Kenya and 8 other countries in eastern Africa. Wolbachia presence was detected in Co. sesamiae populations from Coast and Machakos in Kenya, and from samples collected from 6 other eastern and southern African countries. No infection was detected from western Kenya, Uganda and Malawi. Cross mating among 3 infected populations (North Coast, South Coast and Machakos) and 2 uninfected populations (Kitale and Kuja) was done to establish which populations were reproductively compatible. Biological parameters, such as brood size and percent females were compared among the different crosses. One-way incompatibility, indicative of Wolbachia infection, was observed from the crosses between males of either Mombasa or Machakos arid females from Kitale. Selection of compatible Co. sesamiae populations is critical to successful augmentation biological control programmes.

The relative resistance of rice varieties to Maliarpha separatella was studied during 1981 and 1982 long rain seasons. The observations covered the laying of egg masses, tiller infestation, incidence of “whiteheads” and, in some cases, the grain yield.

The results indicated that the varieties BG 34™8 and BG 90™2 received the highest egg masses per plot which apparently caused “whiteheads”. The remaining 10 varieties only indicated moderate response. The 1982 long rain season under no control and carbofuran 5G application regimes showed reduced tiller infestation only in BG 90™2 and Basmati 217. The five tested varieties did not show any marked difference in tiller infestation under the two regimes. Hence, BG 90™2 and Basmati 217 showed some susceptibility of M. separatella, while the rest of the varieties remained moderately resistant.

Moth population varied according to the growth stages of the rice crop in the field, with the peak occurring during the booting to maturation stages.

Eight potato cultivars namely Anett, Desiree, Feldeslohn, Kerr's Pink, Kenya Baraka, Roslin Eburu, Roslin Gucha and Roslin Tana were tested in the greenhouse to compare their susceptibility to Myzus persicae Sulzer. Differences in the susceptibility of the potato cultivars to aphids were reflected in the number of the apterae aphids that developed on them. Anett, Kerr's Pink and Feldeslohn supported the highest, and Roslin Tana the lowest population of M. persicae. Roslin Tana was found to be resistant. The bottom leaves of most potato cultivars maintained the highest aphid population while the upper leaves maintained the lowest. There were no significant correlations between leaf area and yield of potatoes with the number of apterae aphids on the eight potato cultivars.

This paper is a compilation of abstracts of 91 published articles on the red locust, Nomadacris septemfasciata (Serville) for the period 1940–1998. The summaries have been compiled from material held in the library of IRLCO-CSA at Ndola, Zambia and the University of Zambia, Lusaka. The articles deal with different aspects of the biology, ecology and control of the red locust with about equal coverage.

Insects exhibiting swarming habits in Lake Victoria include mainly the Chironomidae, the Chaoboridae and Povilla adusta (Ephemeroptera). Their early life cycles are spent in the lake as benthos and standard bathymetrie procedures were undertaken to estimate the standing crop biomass of the larvae in Murchison Bay. Povilla was principally a boring invertebrate preferring dried logs (113 g Povilla nymphs per kg of host plant material). Cyperus papyrus carried 5 g C. denudalas 2.5 g and Phragmites mauritanus 1.0 g of Povilla per kg of host plant material. Povilla also occurred in the benthos at 40 g/m2. The Chironomidae and Chaoboridae had a mean standing crop biomass of 80 g/m2 and 3 g/m2 respectively. Their total biomass for the bay was estimated at 16060 metric tonnes for the Chironomidae, 7920 m. t. for Povilla and 660 m. t. for the Chaoborids. Adult swarming habits of the lakefly were closely correlated with lunar phases and the adults were easily trapped at night using kerosene lamps. Biochemical tests of the nutrient value of lakefly showed high levels of protein content (62%), minerals (18%), a low fat content (3.9%) and low moisture content (9%). This makes the lakefly ideal as an additive in animal feeds and growth experiments with poultry and aquaculture fish are currently going on to test the suitability of lakefly as an ingredient in animal feeds.

Factors contributing to host plant resistance in sorghum to Chilo partellus (Swinhoe) were studied. Oviposition on the plants in the field started 3 weeks after germination and peaked 2–6 weeks later. Egg batches (96.1%) were laid on the leaf blades compared with 3.9% on the leaf sheaths. On the leaf blades, significantly more egg batches were laid on the upper (57.2%) than on the lower leaf surfaces. In young plants, leaves attached to the upper and lower segments were preferred for oviposition, while leaves in the upper segments more or less maintained their share of egg batches over time; there was a shift from the leaves in the lower to those in the middle segments with the plant age. Differences among sorghum lines for oviposition were significant and these lines were divided into three categories based on their levels of oviposition.

Sorghum plants reacted to insect feeding in the stem by production of a red staining compound which did not significantly affect the development of the insect. Four damage symptoms were observed and these were related to different plant ages. Plants compensated damage by the production of extra tillers, some of which produced panicles that were ready by approximately the time of harvest. Plants infested 2 weeks after germination produced maximum tillers and juvenile panicles; and also had the least effective tillers, plant heights and grain yields. Grain yields were depressed in the infested plants for the cultivars tested, except in LC 119/80–3 where there were actual grain yield gains.

Leaf-feeding and ‘dead heart’ scores, which were related to reduced plant heights and yields in some of the cultivars tested, are proposed as rational indices for susceptibility ratings and monitoring of crop losses.

At room temperature (diurnal range 23–28°C), Sarcophaga haemorrhoidalis (Fallen) developed from egg to adult in approx. 32 days. Survival ( ± SE%) was generally high (76.63 ± 5.67 for the egg, 80.69 ± 3.20 for the larval and 89.83 ± 3.80 for the pupal stages). Adults emerged over a 4-day period between 07.00 and 13.00 hr local time, with daily peak emergence occurring between 07.00 and 10.00 hr. Their immediate post-emergence period was characterized by a highly active and mobile phase lasting 10–15 min followed by an immobile phase lasting about 1.5 hr. Copulation commenced 4.35 ± 0.43 days after adults emerged and was not preceded by elaborate courtship. After a pre-oviposition period of 12.96 ± 0.47 days, females deposited eggs in batches (1.57 ± 0.23 egg-batches/female) each containing a mean of about 37 ± 4 eggs. Fecundity was 52 ± 6 eggs/female during a mean adult life span of 18.68 ± 1.76 days. Although the foregoing life history parameters are strongly suggestive of K-selected ecological strategy, S. haemorrhoidalis may in fact be adopting an opportunistic r−selected ecological strategy since it habitually breeds in unstable environments.

On exposure of maize grains mixed with groundnut oil at a dose of 20 ml/kg, 100% mortality of the rice weevil, Sitophilus oryzae (L.) was observed within 24 hr and 100% at 10 and 5 ml/kg in 2 and 3 days.

Egg-laying and progeny development in the rice weevils were completely prevented at groundnut oil doses other than 1 ml/kg at which the number of eggs laid and progeny developed were 27 and 38% of those in the oil-free control during the same period. When maize treated with oil at 10–20 ml/kg was reinfested after 19 weeks with fresh adult rice weevils, less than 42% of them had died. The total number of progeny that emerged on week 23 from the two higher doses of oil was 38% of that emerging from the control.

Groudnut oil does not affect the viability of maize grains and damage after 25 weeks. Viability of maize grains was only 6–13% after oil treatment at 10–20 ml/kg compared to 100% in the untreated control.

Interspecific competition within larvae of the fall army worm (FAW), Spodoptera frugiperda (J. E. Smith), by the larval parasitoids, Cotesia(= Apanteles) marginiventris Cresson and Microplitis manilae Ashmead, and the egg-larval parasitoid Chelonus insularis Cresson was studied. Chelonus insularis was not able to compete successfully against Cotesia marginiventris, but was a successful competitor against Microplitis manilae. Multiple parasitization of larvae by either Cotesia marginiventris or Microplitis manilae, which as eggs were parasitized by Chelonus insularis, did not result in additional host mortality. Percentage parasitization under greenhouse conditions by Cotesia marginiventris of larvae parasitized previously by Chelonus insularis was two-fold higher in corn compared to sorghum and more than four-fold higher compared to Bermuda grass and itch grass. The host finding and behavioural sequence of oviposition of Cotesia marginiventris in FAW larvae already parasitized by Chelonus insularis consisted of nine steps. Microplitis manilae females changed their behaviour significantly by displaying a reduction of ca. fifty per cent in host examinations, 45% in ovipositor probes, and 55% in apparent ovipositions when Chelonus insularis parasitized larvae were presented. Cotesia marginiventris and Microplitis manilae exhibited no significant behavioural changes in the per cent contacts, examinations and apparent ovipositions when attacking larvae parasitized previously by either Cotesia marginiventris or Microplitis manilae.

Bruchidius atrolineatus appears at the end of the rainy season when pods of its host plant Vigna unguiculata begin to mature. The eggs are deposited along the ventral suture of pods in the vicinity of the seeds. When the eggs are not attacked by Trichogrammatidae their larvae penetrate the seeds and mortality is low during the post-embryonic development. Most of the adults emerging at pod maturity have functional reproductive organs. In that case the females laid on the same mature pods and larvae develop inside the seeds during the first part of the drying season characterised by high diurnal temperature and low relative humity. If the first emerged adults have functional reproductive organs, the following (60% of the population) are in reproductive diapause. Such diapausing insects have been found during the dry season in shelters near the cultivated fields of Vigna unguiculata. Induction or termination of this reproductive diapause are not yet studied. This diapause probably allows the maintenance of populations during the dry season in absence of host plant.

A preliminary survey was conducted in coastal Kenya to assess the hosts of economically important tick species (Acari: Ixodidae) of domestic animals, as part of a training course for tick scientists from African research institutions. Ticks were collected from domestic animals in Kilifi and Kwale districts.

Eight tick species, namely Amblyomma variegatum, Boophilus decoloratus, B. microplus, R. appendiculatiis, R. evertsi evertsi, R. pulchellus, R. simus and A. gemma were identified. Further, more comprehensive surveys on the hosts, distribution and ecology of ticks of economic importance are recommended.

The effect of pod angle on the resistance of cowpea, Vigna unguiculata (L.) Walp. to the legume pod borer, Maruca testulalis Geyer, was investigated under field conditions at the International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria, using two cowpea cultivars: IT82D-716 (susceptible to borer damage) and TVu 946 (resistant to borer damage). Three different pod angles were used In the study — a normal angle, a decreased angle and an increased angle. Negative and highly significant (P < 0.01) relationships were found between pod angle and per cent pod damage, as well as the seed damage Index In the two cowpea cultivars. Pods with wide angles (≥ 89°) were damaged on only one and rarely on both pods. Apart from biochemical and other bio-physical factors, selection and breeding for wide pod angle is suggested as a strategy for reducing M. testulalis damage to cowpea pods.

Studies involved the evaluation of two types of pyrethroids and two controls in a single study village settlement. A total of 1277 bednets were distributed to 75% of 420 houses in the village, in July 1989, 378 were treated with lambda cyhalothrin (Icon°), 411 with deltamethrin and 331 were untreated. A total of 336 people were not given any nets. Entomological evaluation showed that both pyrethroids have an excito-repellent and lethal effect on mosquito vector species. In assessment of malaria reduction in children as the target group, those sleeping in deltamethrin treated houses showed a greater reduction in parasite rate than those sleeping in lambda cyhalothrin nets: Overall reduction of malaria parasite rate of school children examined was 68%. Biological efficacy in both pyrethroid treated nets persisted over a period of 6 months. Another added advantage was that the individual using the net was protected against mosquitoes and other pests such as cockroaches, fleas, lice and bedbugs. Incorporation of pyrethroid impregnated nets in malaria control programmes involving community participation is recommended.

Chromosomal inversion polymorphism was investigated in samples of Anopheles gambiae sensu lato collected from different localities of Tanzania. An. merus was found monomorphic, while two widespread inversion polymorphisms were recorded in both An. gambiae sensu stricto (2Rb/+ and 2La/+) and An. arabiensis (2Rb/+ and 3Ra/+). Two additional polymorphic inversions (2 Rbr and 2Rq), generally associated, were observed in An. arabiensis from the Rift Valley. Observed karyotype frequencies were in agreement with those expected according to the Hardy-Weinberg equilibrium suggesting conditions of panmixia in both An. gambiae s.s. and An. arabiensis in the studied areas.

Population of Spodoptera litura F. were monitored through pheromone-baited traps during the rainy season 1988 and 1989 in groundnut fields in relation to oviposition on leaves. Four peaks of adult catches were recorded. First and second peaks were smaller and caused no threat to crop. Third peak was observed at the pegging and pod-initiation stage during first week of September and coincided with the greatest oviposition on leaves. The fourth peak was greatest and occurred between 40th and 43rd standard week. However, no oviposition was recorded on groundnut during this period. The moths possibly dispersed and/or migrated to other areas with crops at an appropriate stage of susceptibility.