Life tables of Earias vittella reared on Abelmoschus esculentus L., (okra) Gossypium hirsutum L., (cotton) and Abutilon indicum G. Den. in the laboratory at 27 ± 1°C were constructed. The pest population increased at the rate of 0.124, 0.106 and 0.082 females/female/day, respectively on these seeds. A significant correlation between fecundity and body weight of females raised on these seeds was obtained. The shorter generation time and higher intrinsic rate of population increase on okra seeds shortened the population doubling time of E. vittella to 5.67 days, while the doubling time was 6.64 or 9.00 days on cotton or A. indicum seeds. In a larval period of 16–17 days E. vittella consumed okra, cotton and A. indicum seeds at the rate of 463. 6,493.3 and 382.8 J/g/day. E. vittella fed on okra displayed the highest efficiencies of assimilation (74%), gross (49%) and net production (66%). The efficiencies were comparatively low for the insects fed on A. indicum seeds.

The biological activity of pirimiphos-methyl (20% e.c.) and a chlorpyriphos-methyl/deltamethrin (20/1% e.c.) formulation applied at different concentrations to glass, jute, plywood and mud surfaees against Prostephanus truncatus (Horn) and Sitophilus zeamais (Motsch.), was compared over a period of 18 weeks. The bioassays were conducted at 28°C and 70% r.h., 1, 4, 7, 14 and 18 weeks after treatment. Insect mortality was significantly influenced by the type of surface, the insecticide concentration, the age of the insecticide deposit and the interactions between these factors. P. truncatus was more susceptible to chlorpyriphos-methyl/deltamethrln deposits than S. zeamais. Amongst the different surfaces, glass retained the highest persistence, followed by jute, plywood and mud against P. truncatus. The insecticide deposits on jute were the most effective in controlling S. zeamais.

The effect of resettlement programmes and agricultural development projects on the tsetse population in Gambella were investigated. Adult tsetse were collected using biconical traps and moving vehicle catches. The species collected were Glossina pallidipes, G. fuscipes and G. tachinoides. G. pallidipes was the most frequently encountered species. G. morsitans which were reported to be abundant in the area (Balis and Bergeon, 1968; Hutchinson, 1971; Langridge, 1976) were not collected during the present survey.

About 155,000 ha. of land, formerly reported as tsetse infested, is found to be tsetse free. The natural vegetation is being transformed into farmlands and villages, and the wildlife is being hunted out, remaining only in such areas as Demesaye and Gog forest.

Under such circumstances tsetse hosts may change from wild mammals to man and his domestic animals and outbreaks of nagana and sleeping sickness are likely to occur throughout the region.

The free amino acids of the accessory glands of adult male variegated grasshopper, Zonocerus variegatus (Linnaeus) were investigated at five different ages after emergence of insects maintained oh cassava Manihot esculenta, Cranz using automatic amino acid analyser, Beckman 121 MB. Thirteen amino acid components were consistently detected from days 6 to 28: cystine, aspartic acid, serine, glutamic acid, proline, glycine, alanine, valine, tyrosine phenylalanine, histidine, lysine and arginine. Proline, alanine, glycine, glutamic acid and serine occurred in highest concentrations, comprising 14.27, 11.88, 11.09, 9.66 and 8.15 nmoles respectively throughout the 28-day experimental period. Total free amino acids fluctuated in the course of development of accessory gland with highest load at 28 days of age.

Biochemical approaches have been used to enhance the potency of Bacillus thuringiensis against Plodia interpunctelia. Tests were made with different classes of chemical compounds, characterizedby being safe, non-toxic to man, and cheap in price. Among the tested inorganic salts, calcium carbonate, calcium oxide and zinc sulphate were found to increase the potency of B. thuringiensis δ-endotoxin by 2.5-, 1.9- and 2.7-fold, respectively. With the nitrogenous compounds, the amino acids serlne, arginine, alanine and teucine enhanced the endotoxin effect by 52-, 3.6-, 13- and 1.1-fold, respectively. Also, among the protein solubilizing agents, EDTA and sodium thloglycollate led to a 100- and 2.6-fold Increase in the potency. Formic acid was highly effective among the organic acids used in enhancing the potency, followed by malk acid, with 4.8- and 2.4-fold increase, respectively.

Light and scanning electron microscopy investigations were carried out to identify and count the chemoreceptors on the legs of the tsetse, Gbssina tachinoides Westwood, and topographical maps, considered of value in electrophysiological and behavioural research are presented. The candidate chemoreceptors are located on the femorae, the tibiae and the tarsi and are more abundant on the ventral zone of each segment. The study demonstrates that the prothoracic, mesothoracic and metathoracic legs have a similar number of chemoreceptors and male flies possess more than female (1033 and 570, respectively). The variability of the number of chemoreceptors on the prothoracic legs has been estimated in both sexes.

The phytochemical ptumbagin, isolated from Plumbago zeylanica L., was applied in 2 and 5 μl doses of 0.1% concentration on the surface of Dysdercus koenigii F. adults and its effect on the haemocytes of the bug, studied by transmission electron microscopy. All the five haemocyte types viz. the prohaemocyte, plasmatocyte, granular haemocyte, oenocytoid, and the adipohaemocyte are affected within a period of 24–48 hr. The effect begins with an acute state of vacuolization of the cells and a gradual destruction of the organelles, followed by dissolution of the plasma membrane and passing out of the internal organelles, like the mitochondria and the endoplasmic reticulum. This phenomenon is responsible for a consistent elimination of the haemocytes from the blood, leading to lowering of the resistance and mortality of the insects.

Experiments were conducted in 1989 to evaluate converted sorghum accessions for preflowering extended panicle and soft-dough stage panicle feeding resistance to fall armyworm, Spodoptera frugiperda (J. E. Smith), by incorporating plant tissue into artificial insect diet. Spodoptera frugiperda biological parameters measured were larval and pupal weights, mean duration of the larval stage, time to adult eclosion, survivorship, fecundity, net reproductive rate, intrinsic rate of increase, and relative fitness. The converted lines IS 2246C, IS 2403C, IS 2825C, IS 7007C, IS 8337C, IS 12592C, IS 12612C, IS 12657C, IS 12666C, and IS 12681C were more resistant to both preflowering and soft-dough stage panicle feeding by S. frugiperda than the resistant check NK Savanna 5. The genotypes IS 1340C, IS 2553C, IS 2569C, IS 6911C, IS 7498C, IS 12219C, IS 12617C, IS 12662C, and IS 12664C were more resistant than the resistant check to S. frugiperda feeding in the soft-dough stage, but not in the preflowering stage of panicle development. Plant antibiosis was the major mechanism of resistance in these lines at both stages of the panicle development.

Soybean, Glycine max (L.) Merril, and cowpea, Vigna unguiculta (L.) Walp., were grown in field plots in 1988 and 1989 to compare infestation and damage by pod-sucking bugs (PSBs). Population of PSB was monitored by counting adults and nymphs on rows two and six of each plot from 5 to 14 weeks after planting. Cowpea was infested mainly by Clavigralla tomentosicollis (Stal.), C. shadabi (Germ.), Mirperus jaculus (Thnb.) and Aspavia armigera F., while soybean was infested by M. jaculus, Anoplocnemis curvipes (F.) and Riptortus dentipes F. Soybean had exceedingly low PSB density, ≺ 1 bug/2 m-row, in 1988 and 1989. Four sprays of 400 g a.i./ha. dimethoate had no significant effect on pod and seed damage, yield and germination, compared to the unsprayed control. In contrast, cowpea attracted high populations of PSBs, 30 and 1 bug/2 m-row, in 1988 and 1989, respectively. Dimethoate sprayed against PSBs on cowpea resulted in two- to four-fold reductions (P < 0.05) in pod and seed damage and yield increases of 1500 kg/ha. (P < 0.05) in 1988 and 300 kg/ha. (P < 0.05) in 1989.

Feeding performances of 3509 male and 4838 female sandflies, Sergentomyia ingrami, fed on 46 native or indigenous and exotic or introduced species belonging to 21 families of plants found in Kenya were examined. The results indicated more feeding on certain families than on others. The most used families were Musaceae, Araceae and Compositae, while the least was Alliaceae. A liking for certain species was also detected in families with more than one species investigated. Generally, the most used species were Bidens pilosa (Compositae) and Lycopersicon esculentum (Solanaceae). Interaction between the sex of the sandflies and the tested plants was minimal, suggesting that in most cases males and females had similar species likings. Sergentomyia ingrami fed more on two of the exotic species investigated.

Four calves were infested with larvae of Boophilus decoloratus and Boophilus geigyi on three successive occasions, at 30-day intervals. Results show that the attachment of first instar larvae and survival of subsequent developmental stages (AS), duration of feeding (DF), weight of engorged ticks (WT) and oviposition by engorged ticks were significantly affected when the calves were infested for the second and third time at 30-day intervals with the ticks larvae. After the third infestation, AS was reduced by 48.6%, DF increased by 15.6%, WT and oviposition were reduced by 83.8 and 81.5 %, respectively for B. geigyi. The respective data for B. decoloratus were 48.8, 173, 91 and 80.9%. The tick resistance index (TRI), showed significant reduction to a mean of 0.14 in B. geigyi and 0.076 in B. decoloratus.

The data suggest development of immunity in calves by the first cycle of infestation, inducing resistance against the ticks, which were manifested in subsequent infestations. The use of tick-immunization of cattle for the management of ticks in Nigeria is suggested.