The egg follicle C of the left ovary was developing first, indicating reversed ovarian sequences in 5.8, 4.8, 4.2, 2.2, 1.1 and 2.0% newly-emerged female G. pallidipes from pupae kept at 29.5 ± 0.5, 27.5 ± 1.0, 25.0 ± 0.5, 22.5 ± 0.5, 20.5 ± 1.0°C and then maintained at ambient temperature (19 to 31°C) in the local colony. There was a highly significant positive correlation between the frequency of reversed ovarian sequences in flies and temperature in the range 19.5–30.0°C. The incidence of the abnormality was very low (0.2%) in wild-caught females from the Lambwe Valley, probably reflecting the constancy of favourable temperatures in that location. Old females with altered ovarian sequence had apparently both normal pregnancy and alternate maturation of eggs between the ovaries. This appears to be the first report suggestive of a temperature-induced reversed sequential ovarian development in Glossina.

Feeding deterrency tests by leaf disc dipping method revealed AZT-VR/K extract of azadirachtin as the most potent antifeedant against cabbage butterfly, Pieris brassicae L. larvae. The leaf damage on treatment with the extract (at 3, 2 and 1%) was minimum and ranged between 4.9 and 16.3 % as compared to 98 % in untreated check. High level of feeding deterrency was exhibited at all the concentrations of AZT-VR/K, while in neemark (at 1%) and neem oil (at 2 and 1%), the deterrent effects declined considerably on their decreased concentrations.

Inhabited Macrotermes (Termitidae: Macrotermitinae) mounds in cultivated farms in the humid forest agroecological zones of southwestern Nigeria showed higher clay and silt but lower sand contents than their surrounding soils. These physical characteristics were positively correlated with those of the surrounding soils. The heights and diameters of the mounds were also positively correlated to the level of clay and silt in the surrounding soils, although the correlations were not significant (P > 0.05). Carbon and nitrogen content of 67% of the mounds was lower than that of their surrounding soils. A general increase in exchangeable bases and phosphorous contents of the mound materials compared to those of the surrounding soils was also observed. The pH of mound materials varied between 5.5 and 7.3, with 75% of the mounds having lower pH values than the surrounding soils. The implication of these results on the possible use of mound materials to increase soil fertility is discussed.

Various insect pests, of which stemborers are the most widely distributed and damaging, affect about 30 out of the 35 million hectares planted with maize in developing countries. Chemical control, biological control; cultural methods and host plant resistance constitute the four general approaches to stemborer control. The use of stemborer-resistant maize increases farming efficiency by both reducing yield losses from stemborer damage and reducing or eliminating the cost of insecticides and other inputs. In the past, CIMMYT followed conventional breeding methods to develop germplasm resistant to stemborers and molecular technology, quantitative trait loci (QTL) in marker-assisted selection (MAS) to select for improved stemborer resistance in elite lines. More recently, CIMMYT has developed the capacity to produce transgenic maize with resistance factor(s) derived from genes that encode delta-endotoxins derived from the soil bacterium Bacillus thuringiensis (Bt). A sub-tropical source population with multiple borer resistance (MBR population) was developed by recombination and recurrent selection under infestation with four stemborer species. Marker-assisted selection is being used in two African countries to promote the transfer of resistance into elite and adapted germplasm. The Insect Resistant Maize for Africa (IRMA) project is pursuing the transfer of Bt-based resistance to adapted maize germplasm, initially in Kenya, but later to other interested African countries. CIMMYT's varietal release strategy is to pyramid Bt genes into maize populations with existing multigenic pest resistance, in order to enhance both the levels and durability of plant resistance to maize pests. This paper discusses the various approaches used at CIMMYT to develop stemborer-resistant maize germplasm.

The development of simple models for describing the population dynamics of species with overlapping generations is briefly described. The paper then presents a minimally complex simulation model for tsetse populations in which seasonally varying density-independent mortality, generally applied only to the adult stage, is combined with density dependence acting on both puparia and adults. Density dependence regulates population size within limits determined by an interaction between the strength of the density-dependent relationships and the variability of the seasonal density independence. Population data sets for Glossina palpalis and G. morsitans in Nigeria, and G. pallidipes in Kenya are adequately described by the model. Relationships discovered between the density-independent mortality and climatic variables for the Lambwe Valley data set allow predictions of population changes in other sites on the basis of their climatic conditions. Attempts to predict changes in the population of G.pallidipes in Somalia highlight the difficulties of this exercise. A tsetse's demographic response to climate may vary from region to region, making extensive predictions from local data sets difficult. There seems, however, no need to make more complex models to describe observed changes in tsetse populations.

Incidence of okra stemfly, Melanagromyza hibisci Spencer in India was high (40–60%) in winter months, i.e. during October, November, December and January sowings. Mean maximum and minimum temperature that prevailed 30 days after sowing had significant negative correlation with percentage main stem damage. Carbofuran, phorate, quinalphos and aldicarb, applied at 1 kg per ha reduced damage to main stem at the seedling stage but could not control subsequent damage to petioles. Eurytoma sp., a parasitoid on M. hibisci, had a high density-dependent relationship with its host, and played a significant role in keeping it under control.

Eight cultivars of the common bean (Phaseolus vulgaris L.) and the Tepary bean (Phaseolus acutifolius) were used to study the distribution of puparia of the bean fly species Ophiomyia phaseoli (Tyron) and O. spencerella (Greathead). The puparia of the two bean fly species were distributed differently in the plant, O. spencerella predominating in the root and O. phaseoli in the shoot. There were significant differences between some of the bean cultivars and the number of puparia found. Tepary had the least puparia and P. vulgaris cultivars GLP 806 and GLP 1131 the most. There was a low correlation between the number of puparia and the final yield or root dry weight.

The outbreak areas of the red locust are seasonally inundated wetland areas supporting a rich biodiversity. The potential for environmental damage from the repeated use of broad-spectrum insecticides for locust control in these ecologically sensitive wetlands is therefore great. This paper describes the first trial of a Metarhizium anisopliae var. acridum (LUBILOSA isolate IMI 330189) mycoinsecticide as an alternative, more environmentally benign, intervention strategy for managing red locust populations in their outbreak areas. Following initial bioassay tests in the laboratory, which gave 90–93% kill of 3rd instar hoppers within 6–9 days, an oil based formulation of aerial conidia was applied at a rate of 5 × 1012 conidia/ha using a motorised ‘Solo’ knapsack sprayer to treat 3rd and 4th instar hopper bands in the Buzi outbreak area near Beira in Mozambique. Caged samples of 3rd instars succumbed quickly with a median time to kill of 3.6–3.9 days and 98–100% kill recorded within 8–9 days. The 4th instars took longer to die, with a median lethal time of 5.9–6.1days and > 90% mortality after 21 days. Mortality in control samples was low with 13–23% mortality after 21 days. During this mortality assessment period mean minimum and maximum air temperatures ranged from 26–34°C and relative humidity ranged from 85–100%. Observations on treated bands in the field showed that the cohesion of the 3rd instar bands broke down within 6 days, while controls still behaved normally. Unfortunately observations on the 4th instar band had to be terminated after 10 days due to heavy flooding. This preliminary field trial demonstrated the feasibility of using a Metarhizium mycoinsecticide, applied through conventional spray equipment, for controlling the red locust in its outbreak areas.

The use of fish meal and detergent water has been shown to be simple, economic and reliable for sampling of shootfly populations. Various mixtures of fish meal with other ingredients were evaluated. The most potent mixture was fish meal-yeast-ammonium sulphide, but generally fish meal alone was adequate and the most readily available attractant. The attractance of fish meal was found to be related to its degradation; it increased from the first to the third or fourth day, and then decreased. The chemicals responsible for the attractance of fish meal have yet to be identified, but in all probability they may be the amines resulting from biodegradation of the meal.

The feeding habits and infestation of the bitterleaf weevil, Lixus camerunus Kolbe, were investigated in Rivers State, Nigeria. Vernonia amygdalina was the only species preferred for feeding and oviposition by adult L. camerunus, among the species (Talinum triangulare (Jacq.) Wild, Telfairia occidenlalis Hooker fil, Amaranthus hybridus L., Solanum melongena, Capsicum sp., Chromalaena odorata (Eupatorium odoralum) L., Emilia praetermissa L.) associated with V. amygdalina in farms, that were offered. There was a significant correlation between dry weight of foliage consumed and weight of males and females.

Initial tunnelling direction by larvae was upwards, but on the death of shoots, larvae reversed direction and moved downwards along old tunnels. However, newly-emerged larvae in leaf petioles, tunnelled downwards to the main branch, before pursuing an upward course. In addition to main tunnels, there were also branch tunnels. There was a significant negative correlation between length of tunnel and stem diameter. There was a significant negative correlation between gall/stem diameter ratio and stem diameter.

L. camerunus is widely distributed in the State.

Screening of leishmanial parasites from domestic and wild animals was carried out in Kacheliba, West Pokot District. Spleens and livers of the animals were cultured in NNN diphasic medium. Thin smears of the same tissues were also made and stained with Giemsa stain and examined under microscope. Positive slide smears were obtained from goats and positive cultures obtained in four goats, one rat and two lizards.

After field screening local germplasm for stem-borer (Chilo partellus, Swin.) resistance for four seasons in two years we identified two sources of resistance, Katumani and Kitale. A cross between them performed better than either of the parents. When exotic lines from CIMMYT, Mexico, reported to be resistant to South and Central American stem-borers were screened at Mbita Point Field Station, to test and confirm their resistance to East African stem-borers, a number of them were found to be resistant to Chilo. It was also noted that the level of their resistance was higher and more broadly based than the local source. This shows that the source of origin is always full of genetic variability. This finding now suggests that a cross between the local and exotic sources should offer a wide scope in the multiple resistance or the multiline approach towards pest management.

In south-eastern Uganda the natural hosts of Glossina pallidipes, G. fuscipes fuscipes and G. brevipalpis appear to influence trypanosome infection rates in these vectors. The transmission index of these vectors also differs. Temperature is yet another factor affecting trypanosome infection rates in these tsetses. Other factors probably also form important components in the transmission cycle. In this region of Uganda and its contiguous lake shore area of Kenya there are extant foci of the infections, and man and his symbiotic livestock are exposed to a high challenge of trypanosomiases. Furthermore, in this high endemic/enzootic ecological zone of tropical Africa, the transmission of trypanosome infections to the adventitious hosts, via the tsetse vectors, depends upon a variety of complex interacting factors.

In tomato, infestation by the natural population of the fruit borer, Heliothis armigera (Hubner), on number basis was positively correlated with infestation on weight basis. Infestation was negatively correlated with the number of flowers per inflorescence. Surface texture of calyx also affected the susceptibility of the genotype. Reducing sugars in fruits were positively correlated, while zinc and iron content in foliage and ascorbic acid contents in fruits were negatively correlated with degree of infestation. Coefficient of determination revealed that 87% variability in borer infestation was due to zinc, iron, ascorbic acid and reducing sugar content.

The control of Trypanosoma rhodesiense sleeping sickness by clinical methods is often complicated by the existence of animal reservoir hosts which greatly contribute to the persistence of the disease in many parts of East Africa. The control of sleeping sickness should, therefore, include control of the vector and elimination of the reservoir hosts. Another factor which is often ignored, when planning sleeping sickness control measures, is the influence of cultural practices of the resident human population on the epidemiology of the disease in any given location in East Africa. At Lower Kitete, northern Tanzania, trypanosomiasis due to T. rhodesiense is occupational in nature so that many of the individuals are infected in Lossitete Forest while engaged in various activities. The factors favouring infection within the area, and the role played by the cultural practices of the Masai around the area in bringing about the outbreak of an epidemic, are discussed. The importance of understanding the cultural practices and occupational tendencies of the Masai in Lower Kitete, where trypanosomiasis outbreaks have occurred in the last 10 years, is stressed. With such an understanding the management of trypanosomiasis at Lower Kitete may be successful.

The fat body protein content of silkworms increased with 0.5 μg of thyroxine (T4) per gram of body weight and more so with 1 μg/g on days 4 and 8 after injection. Thyroxine with 1 μg/g dose, however, caused an earlier increase in protein content on day 2. The higher doses of T4 (2 and 5 μg/g) decreased the protein content. All T4 treated groups (except with an ineffective dose of 0.25 μg/g) showed reduced protein level in the adult stage in comparison to the control. Thyroxine with a dose of 0.25, 0.5 and 1 μg/g increased the fat body RNA content over the control level which was observed on days 2, 4 and 8. But on day 13, the RNA content in these groups returned to the control level. Higher doses of T4 (2 and 5 μg/g) decreased the RNA content during the developmental period. DNA content was not altered by lower doses of T4 (0.25,0.5 and 1 μg/g), while the higher doses (2 and 5 μg/g) surprisingly caused a reduction in DNA content during the larval, pupal and adult stages.

The increase in protein and RNA contents with lower doses of T4 and decrease with higher doses, indicates a biphasic nature of thyroid hormone action in silkworm fat body.

A comparison was made of the relative abundance of three species of black-fly pupae colonising three natural substrates in the River Assob, in central Nigeria. Simulium hargreavesi, S. squamosum and S. vorax preferred trailing roots, whereas S. cervicomutum, S. unicomutum and S. impukane preferred dead leaves and to a lesser extent, rocks.

In order to see whether this was a preference between cylindrical and flat surfaces, polythene strips were compared with polythene strings and a smooth surface was compared with a rough one. Results are presented for the three most abundant species S. squamosum, S. hargreavesi and S. cervicomutum. All markedly avoided the rough string. S. squamosum and S. hargreavesi preferred smooth strings, whereas S. cervicomutum had no significant preference between smooth strips and strings (although slightly preferring strips). These findings are discussed in relation to natural habitats and sampling bias.

The length of the reproduction cycle of Lasioderma serricorne (F.) under ambient laboratory conditions (temperature range 28.0–32°C and 72.5–80.5% r.h.)was shown to depend on the identity and state of division of various cereal grains, cowpeas, groundnuts and dried root crops. Cut dried yams allowed the shortest cycle andwholericethelongest.The rate of population increase by L. serricorne was also assessed and this was maximal when cut wheat and minimal when whole rice was provided. Fecundity was highest with sorghum and lowest with rice as food source. Females of the species lived longer than males.

The behavioural process by which a mosquito finds a potential host organism is mediated by olfactory receptors on the insect's antennae. Lactic acid (LA) is a host-related odour common to all potential hosts. On the antennae of the female are two LA-sensitive neurons; one of these is excited by LA but the other is inhibited by LA. Furthermore, the sensitivity of the LA-excited neuron is correlated 1:1 with the presence of host-seeking behaviour such that when host-seeking behaviour is inhibited following a blood meal, the sensitivity of the LA-excited neuron is markedly decreased. The inhibition of host-seeking behaviour and the decrease in LA-sensitivity are induced by a hemolymph-borne factor released during oocyte maturation. The source of this factor is the fat body of blood-fed females, which requires a vitellogenic ovary for its production and/or release. The combined activity of the two types of LA-sensitive neurons together with the shift in sensitivity of the LA-excited neuron from a range where host levels of LA are present to a range exceeding LA levels expected from a host are sufficient to account for the inhibition of host-seeking behaviour following a blood meal.