In Zimbabwe, living and stuffed warthogs (Phacochoerus aethiopicus Pallas) were placed within an incomplete ring of electric nets and observations were made of the numbers of Glossina pallidipes Austen and G. morsitans morsitans Westwood attracted to the hogs, the alighting position and feeding responses of tsetse, and the grooming behaviour of the warthogs. Between 26 and 31% of tsetse landed on the head region of an adult live warthog compared to 8% for a juvenile and 4% for a stuffed warthog. The number of tsetse alighting adjacent to the eye of a stuffed warthog increased 20 times if dark patches were fixed there. The percentage of tsetse alighting on the head region of the adult warthog increased from 25% to 50% as the number of tsetse caught on the ring of nets increased from <100 to > 800. There was a concurrent increase in the rate of skin twitches and ear flicks by the warthog. For an adult warthog, 26% of tsetse leaving the vicinity had fed compared to only 1% for a juvenile. It is suggested that the concentration of tsetse on the head of adult warthogs is a visual response to the dark patch produced by the pre-orbital glands of a mature warthog and to density-dependent changes in the grooming responses of warthogs.

Field studies in Zimbabwe elucidated the responses of Glossina morsitans morsitans Westwood and G. pallidipes Austen to natural and artificial trunks of trees baited with odours of acetone, 1-octen-3-ol and phenols. The numbers of tsetse electrocuted in flight near the base of the trunk increased 2–12 times when the trunk was shortened from 7.2 m to 0.9 m and its diameter was increased from 25 cm to 5 m, when the base was coloured blue or black to contrast with the upper trunk, or when the upper trunk was separated from the base by a gap of 2.7 m. A swarm flying near short trunks was more compact than near tall trunks. Electrocuting grids to catch alighting tsetse indicated that only about 20% of the attracted tsetse alighted on the base of the trunk, whether this was blue or blue/black. Since there is presently no apparent means of cost-effectively avoiding the inhibitory effects of tall trunks, the use of odour-baited trees as baits for tsetse control seems uneconomical.

Africanized honeybees are presently expanding their geographic range within the USA and are considered undesirable due to their substantial defensive behaviour. Africanized honeybees can be differentiated from honeybees of European ancestry using discriminant analysis of morphological characters, based on a minimum of ten intact specimens per colony. In this paper we report a PCR-based method suitable for the identification of African or European mtDNA from sting remnants, such as typically remain on victims following a stinging incident. We experimentally simulated collection and shipment conditions with dried and alcohol preservation of stings, and also report that the method was suitable for sting remnants stored with a victim sample for over one year in alcohol. The determination of mtDNA haplotypes from stinger remnants must be tempered by the constraints inherent in interpretation of mtDNA haplotype data. Such data do not provide any information regarding the genetic contribution of the paternal lineage. However, in geographic areas where baseline information regarding European haplotype frequencies is known, the detection of a different mtDNA haplotype in stingers from a victim, especially when associated with observations of extreme defensive behaviour, would certainly be suggestive of Africanization.

Reports of the African armyworm, Spodoptera exempta (Walker), in eastern Africa for sixteen seasons (1972–73 to 1987–88) were analysed together with weather records to identify the most frequent locations of outbreaks and their relationships with weather. Outbreaks were classified into ‘primary’ outbreaks (derived from low density parent populations), ‘secondary’ outbreaks (derived from previous out breaks) and ‘critical’ outbreaks (leading to many subsequent outbreaks). Differences in seasonal severity of armyworm infestations in relation to the timing and location of primary outbreaks and early season rainfall were also examined. Trajectory analysis was used to estimate migrations of windborne moths, and the distribution of rainstorms was used to help estimate the timing of moth concentration leading to outbreaks of S. exempta. First reported armyworrn outbreaks from October to December in Kenya and Tanzania were usually primary. Critical primary outbreaks mostly occurred in east-central Tanzania, north-east Tanzania and the adjacent Taveta district of Kenya, and east-central Kenya. Strategic control (to prevent subsequent, downwind outbreaks) is best carried out in these areas. Migration direction was largely determined by seasonally dominant winds, although windfield disturbances were occasionally important. Three seasons in which very low numbers of S. exempta were reported, had heavy, persistent October to December rainfall leading to high larval mortality. Seasons with many outbreaks often had rainstorms separated by dry periods, during the rainy seasons.

Catches of Prostephanus truncatus (Horn) and Teretriosoma nigrescens Lewis from 205 pheromone trapping stations in Mexico were compared and related to climate and habitat. Prostephanus truncatus numbers differed between regions and over time with significant interaction between the two. An overall peak in captures occurred between August and November but this was not apparent in Veracruz and Chiapas. Catches of T. nigrescens also differed but effects were less distinct. The peak in P. truncatus catch was related to monthly rainfall and, with a time lag, minimum temperature in the drier, upland regions, but poorly matched in Chiapas and Veracruz. Prostephanus truncatus abundance was predicted from climatic and habitat data during the periods March to 3 July, and 31 July to November. A regression equation derived from temperature, humidity and rainfall, explained 82% of the variance in the P. truncatus catch in the later period. Local habitat made only a small addition to this model. The best correlate of T. nigrescens numbers was the catch of P. truncatus, but it was less abundant relative to P. truncatus as P. truncatus became more numerous and where annual r.h. was above 70%. Predicted abundance of P. truncatus from the regression model is compared with predictions from laboratory studies of reproductive potential under different climatic regimes. While laboratory studies predict high survival in hot, humid areas, the trap data showed higher catches in cooler, more temperate regions. Possible reasons for these differences and implications for the spread of P. truncatus in Africa are discussed.

Following the discovery of Lydella jaliscosp. n. (from Jalisco, Mexico), a parasite of the Mexican rice borer, Eoreuma loftini (Dyar) (Lepidoptera: Pyralidae), the limits of the genus Lydella Robineau-Desvoidy have been widened to include Diatraeophaga Townsend syn. n., Metoposisyrops Townsend syn. n., and Metagonistylum Townsend syn. n. All species regarded as belonging to Lydella are listed, with L. minense (Townsend) comb. n., L. oryzae (Townsend) comb. n., L. scirpophagae (Chao & Shi) comb. n., L. sesamiae (Mesnil) comb. n., and L. striatalis (Townsend) comb. n.

The taxonomy of 10 species of Braconidae (Microgastrinae) which are parasitoids of cereal stem borers in Africa is revised. Dolichogenidea cameroonensis, D. fuscivora, D. oryzae and D. polaszeki, are described as new, Apanteles procerae Risbec is synonymized with Dolichogenidea aethiopica (Cameron) comb. n., syn. n. A key is given and host associations are listed. A summary table of the species mentioned in the text together with their hosts is also provided.

We determined how frequently multiple mating occurs in a field population of Anopheles freeborni Aitken. We used enzyme electrophoresis to analyse field collected females and their offspring, and determined the parity rates of females mating in swarms. The genotypes of progeny in one of the 36 families examined showed conclusive evidence of two sires. 4·3% (n═93) of females mating in swarms were parous, as opposed to 33·9% of host seeking females (n═103). We conclude that multiple mating in A. freeborni occurs at low frequency in the field, and may be ascribed to incomplete transfer of sperm or male accessory gland substance, rather than to routine renewal of receptivity by females.

Biodiversity relevant to pest management of tropical irrigated rice pests is discussed in terms of variation within rice plants, rice fields, groups of rice fields and rice associated ecosystems. It is concluded that, in the unique cropping conditions and stable water supply of tropical irrigated rice, the manipulation of a relatively few manageable components of diversity can confer stability such that pests are mostly kept at levels which do not justify the use of insecticides. Durable rice plant resistance, including moderate resistance, together with ability to compensate for damage by certain key pests, are regarded as fundamental to successful biological control by the natural enemy complex. Reliable natural enemy action is also considered to depend on all-year-round continuity of prey or hosts made possible by the relatively short fallow periods between staggered two to three rice crops per year and by proximity of certain non-rice habitats, notably the vegetation-covered bunds (levées) surrounding each field. In contrast, synchronous cropping could upset stability by destroying the continuity needed for natural enemy success. Such conclusions are supported by the experience of farmers who use little or no insecticide. Much evidence on destruction of natural enemies by certain insecticides supports the contention that insecticide use, especially early in the crop season, upsets natural enemy control of insects such as Nilaparvata lugens (Stål) (Hemiptera: Delphacidae) and also creates heavy selection pressure for strains of pests that can overcome previously resistant rice cultivars. Such circumstances create outbreaks of secondary pests and impair biological control of some key primary pests such as stem borers. It is concluded that pest management of much tropical irrigated rice must be based on natural controls rarely supplemented by insecticides. The success of this approach depends in particular on further research on dynamics of natural enemy and pest communities in rice ecosystems, especially where climatic conditions and water supply are marginally stable. Much more needs to be known about the nature and utilization of rice plant compensation for damage, particularly by defoliators and stem borers. The justification for, and supplementary use of, insecticides needs to be radically reassessed. There is no evidence that a natural control-based approach, as recommended in this review, is incompat ible with farmer practicability or with future developments in rice production technology, except perhaps the possible mechanization-driven increase in field size which would decrease bund area. In contrast, the insecticide-based approach is not only harmful to natural controls but is costly and mostly demands impracticable decision making by farmers on need-based use.