Baiting studies performed in large, medium and small hospitals in Brazil revealed the presence of 14 ant species, with up to nine recorded in one hospital. Dominant species were exotic ants, and in the large hospital, Tapinoma melanocephalum was the most prevalent. Ants were not uniformly spread through the hospitals, but tended to be found in the more critical areas, particularly in nursery, intensive care, obstetrics, neurology and dermatology units. Bacteriological studies using specific media for bacteria associated with intra-hospital infections indicated the potential for the mechanical vectoring of species of Staphylococcus, Serratia, Klebsiella, Acinetobacter, Enterobacter, Candida and Enterococcus by ants. Although T. melanocephalum did not have the highest rate of association with these bacteria, its ubiquitous occurrences resulted in the highest overall potential as a vector of these bacteria. Because of a largenumber of ant species occurring in Brazilian hospitals, ants pose a potential problem to the spread of diseases in hospitals. Because of the number of associated ant species in hospitals, the control of this potential problem is much more difficult than in registered temperate areas.

The eggshells of Sergentomyia minuta, S. schwetzi and S. ingrami are studied by scanning (SEM) and transmission (TEM) electron microscopy. In all three species the surface sculpturing is characterized by a polygonal pattern due to intersecting ridges. Each ridge is formed by columns arranged in palisade and resting on a reticular basal layer. TEM shows that the columns represent the outer chorion and the basal layer the intermediated one. Under these layers an inner chorion and a vitelline envelope are present. The eggshell structures of the three species are compared with those of other Phlebotominae and their taxonomic value is discussed.

The biophysical characters of the mosquito, Culex quinquefasciatus, a dreaded vector of bancroftian filariasis was investigated. The data represents the “system” in bioaerodynamics which comprises the adult mosquito and induced air, and constitutes “action-reaction pair” for the hovering flight. Hence the static and dynamic parameters of this species are determined. An expression for moment of inertia of the flight surface (wing) is deduced considering wing design and geometry. Further aerodynamic requirements in relation to flight performance of the insect are elaborated. It is concluded that this study provides useful information on the hovering flight behaviour of the mosquito C. quinquefasciatus.

Antixenosis component of resistance to corn planthopper, Peregrinus maidis (Ashm.) was investigated in 10 selected sorghum genotypes at three plant growth stages (30,45 and 60 DAG) under laboratory and field (rainy and postrainy seasons) conditions. In a free-choice test, the orientationa) and settling responses of nymphs and brachypterous adults on all genotypes although influenced by the olfactory and visual responses, then- feeding was notsustained due to gustatory stimuli indicating their significant role in determining the degreeof antlxenosis. The genotypes IS 18676, IS 19349 and IS 18677 showed a high degree of antixenosls in settling fewer nymphs and adults consistently at 30,45 and 60 DAG. This finding was supported with low colonization of nymphs, and brachypterous and macropterous adults under field conditions. In addition, high degree of antixenosis for oviposition in both laboratory and field tests was evidenced on IS 18676 and IS 19349 at 30,45 and 60 DAG, but on SPV 472 and SPV 475 only at specific plant growth stages. The variability in the rate of adult colonization together with suitability of plant growth stages for oviposition has contributed to variable degrees of antixenosis for oviposition.

We tested the effectiveness of volatile oils of Lippia adoensis Hoschst, Cymbopogon citratus (DC) Stapf., Eugenia uniflora L., Lantana camara L., and Chromolaena odorata (L.) King and Robinson at a dose range of 5 to 50 p.1 in protecting 9.9 g (50 seeds) of stored cow pea from infestation by the cowpea weevil, Callosobruchus maculatus F. The effectiveness of the oils as fumigants ranked as follows: L. adoensis > C. citratus > E. uniflora. Oils of L. camara and C. odorata were unsuitable for fumigation purposes. At doses of 5 to 20 μl, oil of L. adoensis protected cowpea from weevil attack. At 5 μl, volatile oil of L. adoensis was as effective as 20 μ1 each of E, uniflora and C. odorata, and only slightly inferior to C. citratus. Insecticidal activity of L. adoensis against C. maculatus was unequalled by any other oils tested. The effective doses of these oils did not impair the viability of treated cowpea.

Species of Culicoides feeding on horses were investigated in Ibadan and Ilorin in the southwestern part of Nigeria using light, sticky and emergence traps. A totalof 2949 Culicoides consisting of 22 species were caught over a period of 22 months. Culicoides quinquelineatus was the most numerous, followed by C. imicola. The greatest proportion of Culicoides was caught with the sticky traps followed by the emergence traps during the period of moderate to heavy rains. Males were scarceand the proportion of fed females was generally low.

A significantly greater number of Culicoides was caught during the rains than during the dry season. The results are discussed within the context of previous investigations on Culicoides in Nigeria. The possibility of some species, especially C. imicola and C. quinquelineatus being vectors of African horse sickness is also discussed.

Mating and oviposition of Earias vittella was studied in the absence or presence of the host (okra fruit) or the host odour. When the host was accessible, there was a significant increase in the frequency of copulation, the number of spermatophores transferred and the number of eggs oviposited. Availability of host odour, instead of the host, gave similar results. Further, in general, the number of eggs oviposited by a female was significantly correlated with its mating frequency.

Results of research on biology of Thinophilus guineensis Coul. et Neg. (Diptera, Dolichopodidae) confirm the importance of predaceous feeding behaviour of some other species of Dolichopodidae such as Medetera fisch, Hydrophorus fallen, Sciapus fatten, Diaphorus meigen, etc. Larval mortality of some pests (mosquitoes, blackflies, scolytes, etc.) reach 83 to 99%.

These species, because of their extraodinary ubiquity and their biocoenotical importance, could well be used in biological control programmes of vectors of pathogens affecting man and other animals or pests in agroforestry.

Larval parasitism of the sorghum shoot fly, Atherigona soccata Rondani (Diptera: Muscidae), by Neotrichoporoides nyemitawus Rohwer (Hymenoptera: Eulophidae) was studied in the laboratory. Ten shoot fly larvae of each instar (3) and two periods of exposure (24, 48 h) were used in a factorial design with four replicates. Significant differences of parasitism were observed with respect to instars, periods of exposure, and the interaction instar-period of exposure. The second larval instar was most parasitized (68.75 and 85% of parasitism after 24 and 48 h, respectively), followed by the first instar (46.25% of parasitism) exposed for 48 h to adult parasitoids. N. nyemitawus was an effective shoot fly endo-larval parasitoid. Observations on N. nyemitawus searching sorghum seedlings for shoot fly larvae are summarized.

Studies were carried out to elucidate the parental (vertical) transmission of Nosema marucae Odindo and Jura, in infected females of Chilo partellus Swinhoe. Results indicated that only infected females of C. partellus could pass infection to the offspring. Infection also lowered both the total number of eggs laid per female and egg hatchability- Some adults which developed from the sublethally infected fifth instar larvae of C. partellus had deformed wings while some pharate adults failed to free themselves from the pupal cases. The significance of these deformities to the ecological survival of C. partellus is discussed.

The effect of mixed cropping cow pea with maize on general predators' abundance and their influence on population density of Megalurothrips sjostedti (Trybom) on cowpeas was investigated in the field and in exclusion cages. Populations of predatory ladybird beetles, Orius sp. and earwigs (Dermaptera) were not significantly influenced by mixed cropping. The density of spiders, however, was significantly higher in the cowpea sole crop than in the cowpea/maize mixture. The population density of M. sjostedti was significantly less in the cowpea/maize mixture than in cowpea sole crop, both inside cages, where predators were excluded, and outside. We concluded that this reduced population density was not the result of enhanced predators’ population in the mixture.

The 130 kDa polypeptide appears to be the most susceptible of the polypeptides constituting the Bacillus thuringiensis ssp. israelensis δ-endotoxin to the proteases associated with sporulation. Stabilization of this polypeptide in the recently described K-S sporulation medium has been achieved through limiting its cleavage by removing contaminating proteases from the culture by washing. In this way, the complete δ-endotoxin profile is retained for studies on all of the constituent polypeptide fractions.

Plastic dishes 30 cm dia. and 15 cm depth filled with water as traps for Tropinota squalida Scop, adults and painted blue, green, red, white and yellow were exposed in infested peach areas at Abo-Sultan during 1987–1988. Traps painted blue showed high degrees of attractancy to the pest. White, yellow and green attracted the least number of beetles while red was found to have no attraction. Trapping is considerably influenced by microecological conditions, trap placement and trap diameter. Blue traps (25) were sufficient to suppress the pest population in an infested peach area. Blue trap could be considered as a new forecasting method and for studying the swarming dynamics of T. squalida adults.

Transmission of Ife virus by Aedes aegypti mosquitoes was investigated. Mosquitoes were experimentally infected by feeding on viraemic mice or on infected mouse brain suspended in defibrinated chick blood. Normal infant mice were exposed to infected mosquitoes after predetermined extrinsic incubation period. Ife virus persisted for only 1 day in mosquitoes that fed on viraemic mice and for 5 days in those that fed on infected brain/blood suspension. Virus was not recovered in infant mice exposed to infected mosquitoes. However, there was serological evidence of virus transmission manifested as the presence of complement fixing antibody against Ife virus in mice exposed after 2 days and 2–5 days extrinsic incubation periods to mosquitoes infected by feeding on viraemic mice and by feeding on infected brain/blood suspension respectively. This transmission was considered mechanical in view of the short virus persistence and extrinsic incubation periods.

Observation of the damage caused by Mussidia nigrivenella (Pyralidae) on corn cobs and cotton bolls begun in Togo in 1988 was continued in 1990 and 1991. The study was conducted at IRCT's Anié-Mono station at the Dalanda, Notsé and Kouvé test and on small holdings in the Notsé region. M. nigrivenella is the main pest on corn (over 90% of the caterpillars observed). Its larvae populations were higher in 1991 than in the previous year, owing to favourable climatic and cropping conditions.

On immature cotton bolls, C. leucotreta remains the dominant species. However, the extent of M. nigrivenella activity on mature bolls was revealed for the first time. In certain locations, over 90% of the caterpillars and chrysalids observed in attacked mature bolls belong to this species. Hence, cotton plants which are not destroyed after harvests can act as reservoirs for pyralid pests.

Five natural compounds possessing antiparasitic activity were isolated from East African plants and tested, together with some semisynthetic derivatives, against micro-organisms and arthropods of agricultural interest. Anonaine (1), from Annona squamosa, canthin-6-one(8) and 5-methoxycanthin-6-one (9), from Fagaropsis angolensis, showed fungicidal activity. E,Z-matricarianol (4), from Hoehnelia vernonioides was fungicidal, Insecticidal and acarlcldal. Caryophyllene oxide (12), isolated from Uvaria sp., turned out to be insecticidal and antifeedant. Canthin-6-one (8) and its dihydroderivative 11 were the most effective antimicrobial compounds tested. The possibility ofusing some of the isolated compounds as leads for new synthetic chemicals is discussed.

Newly deposited Glossina morsitans morsitans larvae were chilled over ice and inoculated with 1 μ1 of either virus suspension derived from Glossina pallidipes salivary gland homogenate or sterile tsetse physiological saline. They were allowed to pupariate and then maintained at 25°C, 70% r.h. until soon after emergence when their salivary glands were examined for enlargement and presence of virus particles. Teneral G. m. morsitans which received the virus inoculum (n = 135) as larvae all became infected as revealed by gross hypertrophy of their salivary glands and ultrastructural manifestation of virus particles within the glandular epithelial cells and lumina. In the control group, which received the tsetse physiological saline (n = 91), only 1.1% of the flies showed the salivary gland enlargement, a level equivalent to the prevalence of virus infection normally detectable in the G. morsitans colony. This technique opens the way for testing the biocontrol potential of this virus. The DNA virus from G. pallidipes is clearly infective to G. morsitans morsitans, suggesting that the hypertrophied, chalky-white salivary glands, reported in various Glossina spp., are a manifestation of infection by one and the same virus.

Tetramethrin, deltamethrin and cypermethrin formulated as fumigant tablets or spray(ing) solutions showed flushing out activity on Triatoma infestans. Fumes arising from the tablets were analysed by gas chromatography. The proportion of pyrethroid liberated was between 10 and 20% of the original amount formulated. The flushing out activity shown was dependent on the pyrethroid compound, insect stage and sex. In general deltamethrin proved the most active flushing out agent and cypermethrin the least active. Maximal activity was shown in the combination of nymphs and tetramethrin. Nymphs of Rhodnius prolixus were only flushed out by deltamethrin. In all cases, deltamethrin and cypermethrin yielded 100% mortality 7 days after exposure to the pyrethroid fumes, while tetramethrin was not a killing agent.

Eggs of Heliocheilus albipunctella de Joannis were picked up during ear formation of millet at Bambey in 1988 and were followed up in the laboratory at temperatures 25–30°C and 60–70% r.h. Trichogrammatoïdea sp. probably T. armigera parasitized 60.3% of them. During the period in which eggs were collected, percentage of parasitism increased, which certainly means a build-up of parasite populations.

The growing recognition of problems associated with chemical pesticide use has led to increased attention on integrated pest management (IPM). This paper describes how Tunisian potato farmers have learned to manage an important field and postharvest insect pest, the potato tuber moth, Phthorimaea operculella (Zeller), and how interdisciplinary research on integrated pest management has contributed to this process. During the 1980s, new pest control technology and better farmer awareness led to changes in how farmers manage the potato tuber moth in their fields and stores. Farmers reduced insecticide treatments in potato fields and made more use of agronomic practices to avoid crop losses from the insect pest. New government regulations and agricultural extension efforts have caused farmers to discontinue use of environmentally harmful chemicals such as DDT. Research is continuing on biological insecticides that are not toxic to mammals and some farmer adoption of these products has occurred.