—The possible immune responses of insects to some abiotic agents were reviewed. These agents include insecticides, insect growth regulators, antibiotics, inert particles and miscellaneous substances of particulate and non-particulate nature. The significance of studying the immune response of insects to abiotic agents in relation to insect control, together with the link between the immune response of insects to both abiotic and biotic agents is discussed.

Fluoride accumulation and the relative fluoride loading of different body parts in the wild mulberry silkworm (Bombyx mandarina M.), mulberry geometrid (Pathonandria atrineata B.) and mulberry silkworm (Bombyx mori L.) near fluoride pollution sources in the main sericultural region of China were studied. The results showed that the insects had an increased fluoride accumulation if compared to their feed, and that there were wide differences between the different insect species with the same feed and within the same polluted site. The digestive tract of the insect retained much higher fluoride content than other body parts. Moreover, a highly significant correlation was found between fluoride content in the studied insects and that of the mulberry leaves on which they were collected. Of the three insects studied, the mulberry geometrid appears to be most adapted to environmental fluoride, while the domestic silkworm is the least able to tolerate high fluoride levels, experiencing high mortalities at 94.3 mg/kg.

Mulberry (Morus spp.) was found to be the most sensitive plant to air-borne fluoride pollution among six plants studied in polluted areas, and could be a useful bioindicator to monitor environmental pollution. The highest fluoride content was found in the oldest leaves, and in plants growing closest to and downwind from the pollution source.

Mites are known to live in a diverse number of habitats, but only recently have they been collected in large quantities from the tropical canopies, where they have a diverse feeding habit.

We studied the canopy oribatid mites from five localities of Mexican oak species. Foggings with a natural pyrethrum in aqueous solution were employed to obtain the arthropods living on the canopy of the oaks. Specimens were taken from two collections made in February and August of 1997.

The total number of mites obtained with the two foggings was 5824 specimens. Most of them (95%) were collected during the rainy season and only about 5% during the dry season. The Mesostigmata were represented by 194 specimens, Prostigmata by 849 and the Cryptostigmata (or oribatids) were by far the most abundant, with a total of 4781 specimens. This group represents only 3% of total mite abundance during the dry season and 97% during the rainy season.

Quercus crassipes harboured more oribatid mites during the dry and rainy seasons, and the most important mites in abundance and frequency were Camisia sp., Phauloppia sp. and Scapheremaeus sp.

Based on the systematic study of the nature of symptoms and extent of damage, a rating scale of 1 (healthy plant) to 9 (deadheart) was developed to allow the screening of maize genotypes for resistance to the pink stemborer, Sesamia inferens (Walker). The maize plants were separated into three distinct groups, namely least susceptible (1–3 score), moderately susceptible (4–6) and highly susceptible (7–9).

Studies were conducted in farmer's field, Lambwe School of the Deaf, and Mbita Point Field Station of ICIPE (ICIPE-Mbita) in western Kenya during the long rains of 2001 and 2002 to assess the impact of a diversionary stemborer management strategy on the pest's predators. Treatments consisted of a maize monocrop (control) and an intercrop of maize and desmodium, Desmodium uncinatum Jacq., with Napier grass, Pennisetum purpureum (Schumach), as trap crop around the field (‘push-pull’) in the farmer's field and Lambwe School of the Deaf. Sudan grass, Sorghum vulgare sudanense (Pers.), was used in place of Napier on the station. A combination of sticky traps, direct observation and hand-collection methods were employed. Predator groups encountered included 12 families from 7 insect orders and 4 families from one arachnid order, with most of the foregoing represented in both maize monocrop and ‘push-pull’ plots. A Cheilomenes sp. and Chrysopa sp. were, however, recovered from ‘push-pull’ plots only. Ants, earwigs and spiders were the main predators encountered. Both overall and individual group populations of these predators as well as ant diversity were significantly higher in ‘push-pull’ than monocrop plots in all the sites during the vegetative, flowering and mature maize growth stages (P < 0.05, t-test). The results thus indicate a numerical enhancement of stemborer predators by use of this habitat management system.

Molecular clocks based on sequence change in mitochondrial (mt) DNA have been useful for placing molecular phytogenies in their historical context, thereby enhancing evolutionary insight. Nonetheless, despite their importance to phylogeographers, the methodology is controversial. Here we report on two mitochondrial clocks for the butterfly genus Danaus based on sequences from the cytochrome c oxidase subunit I (COI) and small subunit 12S rRNA (12S) genes. Both clocks are, within the context of Danaus, reliable time-keepers, mutually consistent and, respectively, in agreement with a crustacean COI clock and a molluscan 12S clock. Though we have no fossils with which directly to calibrate sequence divergence rates for Danaus, the 12S molluscan and COI crustacean clocks chosen for comparison were calibrated to radiometrically dated geomorphological events. Our results indicate that the Danaus COI clock evolves approximately four times faster than the 12S clock. Differences between rates of sequence change in terminal sister-taxa are small and likelihood ratio tests do not reject a hypothesis that evolution has been clock-like. The species Danaus chrysippus is paraphyletic and, therefore, invalid. Danaus probably split from its sister-genus Tirumala around 4.9 ± 0.3 million years ago in the early Pliocene.

Investigations were conducted to establish field responses of Glossina pallidipes, G. m. morsitans, muscoids and tabanids to castor, raw linseed, paraffin and chlorinated paraffin oils in deltamethrin suspension concentrate (sc) formulation, through randomised Latin square experiments. Tsetse landing responses on targets treated with 400 ml/m2 of any of the oils in 2 g/m2 deltamethrin formulation were significantly lower than on non-oil-containing deltamethrin formulations, for both G. pallidipes (F(4,32) = 4.855, P = 0.00357) and G. m. morsitans (F(4,32)=2.421, P = 0.06862).

The landing response indices, relative to the control formulation without oil, were 0.60, 0.70, 0.61 and 0.41 in G. pallidipes and 0.92, 0.82, 0.75 and 0.42 in G. m. morsitans and for paraffin, chlorinated paraffin, castor and raw linseed oils respectively. Glossina pallidipes and G. m. morsitans landing responses were inversely proportional to raw linseed oil concentrations. None of the oils significantly affected muscoid (F(4/32) = 1.6959, P = 0.1753) or tabanid (F(4,32) = 1.7546, P = 0.1624) landing response, or tsetse fly resting persistence (F(4,32) = 0.9641, P = 0.4406) on the targets.

The reduced tsetse fly response to targets treated with any of the oils can be attributed to adverse effect of the oil treatments on the tsetse fly olfactory responses to the targets. Since the oil formulations reduce target efficiency by reducing tsetse responses to the targets, application of the oil formulations on targets deployed in G. pallidipes and G. m. morsitans control programmes is not recommended.

The eggshell fine structure of a lepidopteran pest of mulberry, Amata passalis F. (Lepidoptera: Amatidae), was investigated using scanning electron microscopy. The micropylar rosette around the micropyle, shell imprints, aeropyles and regional differentiation were studied. The surface of the amatid eggshell had a highly decorated chorion with structural difference at the anterior and posterior poles. The micropylar structure was at the anterior pole of the spherical eggs (488 ± 0.595 mm in diameter), opposite to its side of attachment to the substratum. The micropylar rosette measured 51.20 ± 0.52 mm in diameter and was formed of 15–19 petal-shaped primary cells. The micropylar opening into the micropylar canal was 3.76 ± 0.52 mm in diameter. The entire surface of the chorion had a reticulate pattern of pentagonal and hexagonal cells, each of which was boarded by 3 to 6 aeropyles of similar size (0.36 ± 0.008 mm in diameter).

Various morphological characters of larvae of Aedes (Stg.) simpsoni complex collected from different localities in Uganda were studied in an attempt to characterise the species in the Ae. simpsoni complex. Morphometrics of larval characters revealed wide ranges of variation most of which separated or grouped populations. Multivariate discriminant analysis and principal component analysis discriminated between different populations. In some populations the males were fairly distinct from the females, while for some characters the populations overlapped considerably. The percent variability of each character alone is low and does not separate the species of the complex. However several characters correlated. Length of antennae (LANT), length of antennae up to Seta 1–4 (LANT4), length of head (LHEAD), and length of siphon up to position of Seta 1-S (LSIPHSET1S) showed fairly significant variability which could be used in conjunction with characters of pupae and adults to separate populations. In the wild we find anthropophilic and non-anthropophilic populations of the mosquitoes, especially in Colocasia plants, bananas (Musa sp.), Dracaenia and Ananas sp. The multivariate analysis carried out could not separate the populations into biting behaviour groups nor breeding habitat groups.

The traditional values of caterpillars to the Bisa people of northern Zambia were assessed through a questionnaire survey involving 104 households from 24 villages. Information validation was by Participatory Rural Appraisal, Focus Group Discussions, caterpillar collection and identification. Caterpillars of eight Saturniidae moth species are valued very highly by the Bisa. Six of these were collected and identified from the miombo woodlands of the study area. The harvesting of Gynanisa maja (Klug), Gonimbrasia belina (Westwood), Cirina forda (Westwood), Imbrasia epimethea (Drury), I. rubra (Bouvier) and Imbrasia sp.3 caterpillars by local people, provides an alternative source of dietary animal protein and is associated with several cultural and spiritual processes and beliefs which bind the people together as one tribe. Edible caterpillars are bartered and sold at markets, enabling the local people to gain access to goods and services that normally are out of their reach. An individual collector processed 11.5 kg of sun-dried edible caterpillars worth Zambian Kwacha (ZK) 172,600 (US$ 52) during the caterpillar-harvesting period in 1999, while a household averaging six members processed 69.1 kg caterpillars worth ZK 1,036,098 (US$ 309). The income generated from sales of edible caterpillars far outstripped that generated from the sale of agricultural produce. Estimates of household incomes for 1999, an edible-caterpillar bumper harvest year, and the Bisa traditional edible-caterpillar management system are discussed.

A new fruit fly species suspected to be from the Bactrocera dorsalis (Hendel) group (originating from Asia), was detected during routine field surveys in the Coast Province of Kenya. Since most species in this group are of tremendous quarantine concern when introduced, and considering the fact that it has never before been detected or reported in continental Africa, surveys were immediately initiated covering a distance of over 3000 km across major fruit-growing and trading localities within Kenya, to determine the extent of spread of the new invasive species. We report on the detection of the flies, preliminary results of the survey, and discuss the potential effects of these flies on the horticulture industry in East Africa.