Data on insects as food in sub-Saharan Africa were collected by reviewing the literature and conducting interviews in a number of African countries. A list of about 250 edible insect species from Africa was compiled. Of these, 78 percent are Lepidoptera (30%), Orthoptera (29%) and Coleoptera (19%), and 22 percent Isoptera, Homoptera, Hymenoptera, Heteroptera, Diptera and Odonota. Insects are rich in protein, vitamins and minerals, and a good source of iron and B-vitamins. Examples of insects being toxic are given, but often traditional methods are used to remove the poison. Whether or not insects are eaten depends not only on taste and nutritional value, but also on customs, ethnic preferences or prohibitions. The harvesting of insects is often done by women. The way of collecting depends on insects' behaviour. For example, inactivity at low temperatures enables easy catching of locusts and grasshoppers in the morning. Night flyers (termites, some grasshoppers) can be lured into traps by light and some insects like palm weevils can be attracted to artificially created breeding sites. Some species (crickets, cicadas) can be located by the sound they make. A number of tools are used to facilitate capturing such as glue, sticks, nets and baskets. Because most insects are only seasonally available, preservation by drying is often practised. Some examples of how to prepare them as food are given from important insect groups.

To manage insects in the interest of food security more attention should be given to environmentally sustainable harvesting methods. They should be made better available throughout the year by developing improved conservation methods or by farming this minilivestock. Considering the economic, nutritional and ecological advantages of this traditional food source, its promotion deserves more attention both from national governments and assistance programmes.

The study reported here evaluated the distribution, relative abundance, and malaria transmission potential of Anopheles mosquitoes at 30 sites representing different ecological strata in western Kenya. Seasonal variation in anopheline densities and transmission potential, as expressed by Entomological inoculation rates (EIR), was investigated. Of the 6491 indoor resting anopheline mosquitoes collected at the 30 sites, 91.3 % (n = 5926) were An. gambiae s.l. and 8.7 % (n = 565) were An. funestus with an average house density of 6.58 and 0.63, respectively. Analysis of the data indicated significant variation in mosquito densities between study sites, species and season. High densities of both An. gambiae and An. funestus were recorded in the northern and northeastern parts of the district, while generally low densities were recorded in the south. Anopheles gambiae s.s. and An. arabiensis comprised 60.3 % (n = 3573) and 39.7 % (n = 2352) of the total number of An. gambiae s.l. mosquitoes collected, respectively. The composition of the An. gambiae s.l. sibling species showed temporal and spatial variation. Entomologic inoculation rates were estimated at 1.55 and 0.12 infective bites per person per month for An. gambiae s.l. and An. funestus, respectively. This study reveals considerable seasonal and site-specific variation in vector distribution, composition and transmission potential. Application of control interventions must therefore consider seasonal variations since the vectorial system changes quite rapidly over a short period of time.

We have previously described a bloodmeal-induced molecule (lectin-trypsin complex) from the midgut of the tsetse fly, Glossina longipennis, with both lectin and trypsin activities (Osir et al., 1995). In this paper, we report on the isolation of a similar molecule from the midguts of Glossina fuscipes fnscipes and provide direct evidence for its involvement in the development of African trypanosomes. The molecule (native Mr ∼65,700) has two non-covalently linked subunits, Mr ∼28,800 and Mr ∼35,700. The native molecule was found to be capable of inducing differentiation of bloodstream-form trypanosomes into procyclic (midgut forms) in vitro. In the assays, specific antibodies against procyclin were used to monitor the transformation of the bloodstream-form trypanosomes into procyclic forms. This induction was specifically inhibited by D-glucosamine. Cis-aconitate was also capable of inducing the transformation process with the same efficiency as that of the lectin-trypsin complex. While increasing the concentrations of the lectin-trypsin complex (≥100 μg protein/ml) in the incubation assays resulted into higher transformation rates, it also led to high parasite mortality. These results provide evidence for the involvement of the midgut lectin-trypsin complex in the differentiation of bloodstream-form trypanosomes within tsetse midgut.

The biological hypothesis that female parasitoids can adjust their fecundity schedule according to host availability, and tradeoff longevity with fecundity was tested in a thelytokous oophagous parasitoid, Trichogramma brasiliensis Ashmead (Trichogrammatidae: Hymenoptera) parasitising the rice moth, Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae). The tradeoff between early and late reproduction revealed that this wasp was able to exploit practically all available hosts during the first day or first few days of adult life. During spells of host unavailability, it was able to adjust its fecundity schedule accordingly. There was a negative relationship between survival and reproduction. Adult females survived shorter (10 days) when an unlimited supply of hosts was present, but longer (16 days) when no hosts were provided. These observations suggest the potential suitability of T. brasiliensis for inundative releases even in conditions of fluctuating host availability.

The ovipositional orientation of an aphidophagous ladybird beetle, Propylea dissecta (Mulsant) (Coleoptera: Coccinellidae) in terms of geo- and photo-taxis, colour and texture of substrates was studied. The beetle exhibited a high preference for negatively geotactic substrates for oviposition. There was no clear preference for positively or negatively phototactic substrates. When studied in combination, it was observed that substrates that were negatively geotactic were preferred over other substrates regardless of the phototaxis. Red was highly preferred over the other 5 colours tested, and plastic was the substrate of choice for P. dissecta oviposition.

The population dynamics of busseola fusca (Fuller) was studied from 1997 to 1999 at Halhale and Halhal Begos, located at altitudes of 1960 and 1850 m above sea level respectively in the highlands of Eritrea. Sowing was done in early April in Halhale and late June in Halhal Begos throughout the study period. All agronomic practices recommended for sorghum production in the two areas were followed to ensure good crop stand, except for application of pesticides. A total of 15 generations, nine in Halhale and six in Halhal Begos were observed during the study periods. Busseola fusca had three and two generations per year in Halhale and Halhal Begos, respectively. Peak egg laying at Halhale was in early May, July and early September, while at Halhal Begos it was in July and early September. The study revealed that stage-specific mortalities of B. fusca were caused by infertility, disappearance (predation by ants and earwigs, lack of suitable host, abiotic factors), residuals and parasitoids. The key mortality factor was disappearance of small larvae (35–66 % mortality). The mortality of the other stages was low but had a composite effect on the overall generation mortality. The mortality of small larvae was density-dependent and density-independent at Halhale and Halhal Begos, respectively. The changes in population between generations were due to small larval mortality of B. fusca from one generation to the next. The life table study showed that mortality due to natural factors did not reduce B. fusca population below the damage level. Integrated management strategies are discussed to reduce the damage caused by B. fusca on sorghum.

In West and Central Africa, panicle-feeding mirid bugs, particularly Eurystylus oldi Poppius (Hemiptera: Miridae), are major pests of improved sorghum cultivars. Population dynamics of panicle-feeding bugs were studied on the sorghum cultivar ICSV 197, sown on eight dates each year from 1992 to 1994 at Samanko, Mali. Relationships between weather factors and abundance of paniclefeeding bugs were examined for the three most commonly found mirids, E. oldi, Campylomma spp. and Creontiades pallidus Rambur (representing on average respectively 58, 39 and 2% of all mirid species). Although only one generation of E. oldi could develop between flowering and grain maturity on a particular panicle, there were three successive generations each year during the extended grainmaturing period in the experiment with eight sowing dates, with a major peak in abundance in early October, followed by a gradual decrease until late November. Abundance of Cr. pallidus peaked in late October, while that of Campylomma spp. showed no relationship with date of sowing.

An increase in abundance of E. oldi nymphs (y1) was favoured by high precipitation, reduced maximum temperature and high minimum relative humidity during and 2–3 weeks before the grainfilling period [a strong negative relationship was found with the number consecutive days without precipitation from 78–88 days after sowing (das) (x1): y1 = −11.7x1 + 149.3 (r2 = 0.67)]. The abundance of Cr. pallidus (y2) was correlated with wide temperature ranges and low precipitation during the same periods (notably precipitation frequency from 75–91 das: x2): y2 = −2.28x2 + 24.6 (r2 = 0.65). The abundance of Campylomma spp. (y3) was negatively correlated with amount of rainfall between 19–32 das (x3): y3 = −3.82x3 + 705.9 (r2 = 0.49). Reasons for these trends are suggested and their possible application for management of panicle-feeding bugs discussed.

The relationship between abundance of the lepidopteran borers Helicoverpa armigera Hubner and Maruca vitrata (Geyer) and damage and yield loss in short-duration pigeonpeas was studied in two multilocation trials in 1995–1996 and 1996–1997 rainy seasons at four locations in India: Patancheru (Andhra Pradesh), Akola (Maharashtra), Sardarkrishi Nagar (Gujarat) and Vamban (Tamil Nadu). Larval populations of Helicoverpa armigera (Hubner) and Maruca vitrata (Geyer) were correlated with pod damage and grain yields. Significant correlation of location, years and genotype on insect population, level of damage and grain yield was obtained. The effect of plant type on lepidopteran pod damage was also observed. The relationships between pod damage, yield and larval population of Helicoverpa and Maruca are discussed.

Studies were conducted at the ICRISAT Sahelian Centre, Niger, to assess damage and yield loss by the millet stemborer, Coniesta ignefusalis (Lepidoptera: Pyralidae) on Pennisetum glaucum (L.) R. Brown. Although 78% of stems were infested, late attack by the millet stemborer on millet plants resulted in bored stems yielding more than unbored ones. Artificial infestations with 5 and 10 larvae per plant at 2 weeks after plant emergence (WAE) resulted in 50 to 70% plants with deadhearts and 24 to 100% avoidable yield loss. At 4 weeks after plant emergence, infestations with 5 larvae and 10 larvae per plant resulted in 7% increase in yield and 16% yield loss, respectively. Therefore, both the age of plant and density of borer population at the time of infestation can influence resulting stemborer damage and yield loss on pearl millet.

The spatial distribution, pupation behaviour and natural enemies of Cirina forda in the soil around its host, the sheanut tree, Vitellaria paradoxa were investigated in the field. Results indicated that final instars pupated within a 6–15 cm depth of soil located within a 90-cm radius around the host tree. Pupal density was significantly higher (P < 0.05) in soils on the north and west axes than on the south and east axes around the host tree. Pupal mortality was significantly higher within the top 5 cm and beyond a 16 cm depth of soil around the host tree. Four fungal pathogens, Trichoderma sp., Aspergillus nigers, A. flaus and Fusarium solarti isolated from diseased larvae were implicated in the significantly high larval and pupal mortality that occurred within a 90-cm radius of the host tree trunk. Percentage field parasitism of the eggs by a parasitic wasp Entedon sp. (Hymenoptera: Eulophiidae) averaged 18%. Investigation on the potential of these microorganisms for biological control of C. forda is ongoing. An integration of effective biocontrol agent(s) with a slow release insecticide with a penetration depth of 15–20 cm could form part of an integrated management plan for the pest.

M. Knapp and S. S. Kashenge

Effects of different neem formulations on the twospotted spider mite, Tetranychus urticae Koch, on tomato (Lycopersicon esculentum Mill.)

The equation for calculating repellence, shown on page 3 of Insect Science and Its Application, Volume 23 Number 1, under the subheading “Repellence and Oviposition Deterrence” should read: