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.

Sorghum head bug, Calocoris angustatus Leth. (Hemiptera: Miridae) is an important insect pest of sorghum in the semi-arid tropics. A technique to screen for resistance to head bugs under field conditions was tested. Planting infester rows of susceptible cultivars (CSH 1 or CSH 5), 20 days before the test material or planting early (40–45 days) flowering lines (IS 802, IS 13429 and IS 24439) along with the test material, split planting of test material at 15-day intervals, grouping test material according to maturity, and use of sprinkler irrigation to maintain high humidity, were found effective in increasing the efficiency of screening and selecting for resistance to head bugs.

A headcage technique to screen for resistance under no-choice conditions has also been developed. Panicles infested with 10 pairs of bugs at pre- and half-anthesis, result in maximum population build-up and grain damage under headcage. This technique is useful for confirming the resistance observed under field conditions.

Under natural infestation, five genotypes harboured relatively lower head bug numbers than the susceptible checks, but only three (IS 17610, IS 17618 and IS 17645) maintained their level of resistance under the headcage. Seed germination was > 70% in these genotypes compared to < 10% in CSH 1 and CSH 5.

Observations on the reproductive behaviour of the armoured ground cricket, Acanthoplus speiseri Brancsik were made in the laboratory and field. In the field a male ready to mate attracted both receptive females and mature “silent males” by stridulating. A receptive female moved to the stridulating male and upon reaching it courtship begun. Silent males also moved towards the stridulating male, but stopped at a mean distance of 1.07 ± 0.14 m from him and either seduced females that passed their way to the stridulating male, to copulate with them, or joined the stridulating male singing. Chorusing of the calling song involving more than two males was not uncommon in both the field and laboratory.

Due to stiff competition for mates in the environmental chamber in the laboratory male A. speiseri combined acoustic and substrate signals to attract receptive females. The male ground crickets vibrated their appendages, while they stridulated. Substrate signalling through body/appendage vibration or tremulation is here being reported for the first time in the tettigoniid subfamily Hetrodinae, to which A. speiseri belongs. The courtship behaviour, orientations of members of a copulating pair relative to each other, copulation, spermatophore transfer from the male to the female during copulation and oviposition and postoviposition behaviours of the species are described. Finally, the differences in the reproductive behaviour of A. speiseri in the field and laboratory are discussed.

Five populations of the tick, Rhipicephalus appendiculatus (collected from Kilifi, South Nyanza, and Uasin Gishu districts, and a Muguga laboratory strain) were subjected to isoenzyme analysis. Isoelectric focusing (IEF) of 11 enzymes on agarose gels was used to determine genetic differences between the tick populations. The isoenzyme profile results of the 11 enzymes investigated indicated that four loci, peptidase 1 (PEP 1:EC 3.4.11.1), PEP 2:EC 3.4.11.1, malate dehydrogenase (MDH:EC 1.1.1.37) and glucose phosphate isomerase (GPI:EC 5.3.1.9) showed differences in the populations. The Uasin Gishu population was distinct from all others. Ten out of the eleven enzymes studied were polymorphic in most of the populations while only one (i.e. PEP 7) was monomorphic.

Adult female Rhipicephalus appendiculatus ticks were fed on rabbits immunized with either bovine serum albumin, solubilized tick midgut membrane proteins, a 50:50 mixture of bovine serum albumin and solubilized tick midgut membrane proteins or buffer. Haemolymph harvested from these ticks after they had fed to engorgement and sera from the immunized rabbits were assayed for the presence and quantity of both the total rabbit IgG and specific rabbit IgG raised against bovine serum albumin using the enzyme linked immunosorbent assay technique. The results obtained indicated that rabbit IgG was able to cross the midgut barrier of the tick into the haemolymph. Furthermore, the amounts of IgG crossing into the haemolymph were dependent on the antibody titres in the serum. The results also showed that feeding ticks on blood containing anti-tick midgut antibodies increased the passage of IgG into the haemolymph.

The juvenile hormone analogue (JHA) 6′, 7′,-epxy-3, 7′-dimethyl-undec-2′-enyl 6-ethyl-3-pyridyl ether at 10 ppm (v/v) applied to whole wheat grains was not toxic to adult insects, but effectively reduced the F1 generation of the lesser grain borer, Rhizopertha dominica (F.). However, topical applications of 4 ppm (v/v) of the JHA prevented normal metamorphosis of the larvae and pupae; all the test insects died due to morphogenetic abnormalities induced by treatment with the JHA.

The cotton boll worm, Heliothis armigera Hbn, was grown under standard conditions. Parameters are given for identification of larval instars on the basis of head capsule width. Intrastadial weight of larvae in terms of fresh weight is presented for a regular time interval of 12 hr. The maximum larval growth in all the stadia was observed in the first 24 hr after the preceding moult. Weight of larvae was almost constant in the last quarter of the stadium, till they moulted into the next. Although the last instar larvae gained maximum weight amongst all the stadia, their actual growth was minimum. First instar larvae recorded a 13 times increase in body weight in comparison to the last instar larvae with 3.9 times. Fifth instar larvae entered into the prepupal stage after they had completed an age of 60 hr. Temperature had a profound influence on the incubation period of eggs; the higher the temperature, the shorter it was. Between 28 and 36°C the incubation period was almost the same. The maximum tolerance level of constant temperature for the eggs of Heliothis armigera was 37°C.

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.

Two juvenile hormone analogues (JHAs), R-20458 (6, 7-epoxy-l (p-ethylphenoxy)-3, 7-dimethyl-2-octene) and ZR-512 (ethyl 3, 7, ll-trimethy1-2, 4-dodecadienoate) were topically applied to various instars of mustard aphid, Lipaphis erysimi (Kalt), delivering doses ranging from 0.000015 to 1.0 μg in acetone on the dorsum of each test insect with the help of a microsyringe. Deformed individuals were categorized as adultoids (crumpled and twisted wings), nymphal-adult intermediates (sclerotized wing pads) and supernumerary nymphs (one extra moulting) and a scale was devised to asssess the extent of deformities. The process of embryogenesis was observed to be normal and the adultoids and nymphal-adult intermediates (with normal gonopores) reproduced normally. Only in case of supernumerary nymphs where gonopores were absent and those intermedites which had occluded gonopores, parturition could not take place. Antennae, legs and cornicles of the deformed individuals also exhibited some degree of deformation due to the hormone treatment. The third, second, fourth and first instar aphids ranked in descending order in developing abnormalities under exposure to the JHAs; a dose as low as 0.000015 μg/aphid of ZR-512, significantly deranged the morphogenesis of the third instar aphids. The lowest doses imparting significant degrees of abnormality to the aphid were 0.0039 and 0.00006 μg/aphid for R-20458 and ZR-512, respectively; showing the latter as more potent agent of morphogenetic abnormalities.

The effects of six constant temperatures ranging from 15 to 40°C on the rate of development, progeny production, sex ratio and adult longevity of the grape mealybug parasitoid, Anagyrus dactylopii (How.) were determined. It was found to complete the development in the temperature regimes of20–35°C but neither sex emerged as adults at 15 and 40°C. Developmental time of male and female decreased from 32.75 to 10 days, and from 34.50 to 11.75 days respectively, as the temperature increased from 20–35°C. Progeny production increased with the rise in temperature up to 30°C, and a maximum of 182 offspring emerged at 30°C. Sex ratio was altered considerably by different temperatures. Maximum female progeny was also obtained at 30°. Adult longevity of both sexes declined with increasing temperature. Mean longevity of male reduced from 2730 days at 15°C to 2.75 days at 40°C. The findings on the effects of temperature in relation to the rearing in the laboratory and the activity of Anagyrus dactylopii in the field are also discussed.

Interspecific attraction between Earias vittella and Earias insulana was studied by conducting sex pheromone bioassays and by making visual observations on the behaviour of individual interspecific pairs. Olfactometer bioassays using virgin “calling” females revealed interspecific attraction amongst about 10% males. In bioassays using female sex pheromone, E. insulana did not attract any E. vittella males, but the E. vittella female sex pheromone attracted 8.7% interspecific males. Electroantennogram recordings revealed detection of interspecific sex pheromones by antennae of males of both the species. When kept at a close range and allowed free access to interspecific females, more than 50% of E. insulana males courted and copulated with E. vittella females, but incidence of such courting and copulation was negligible in the reciprocal cross. In both the cases, there was no interspecific insemination. These studies suggested that dissimilarities in: (a) sex pheromone components or their ratio, (b) courtship behaviour and (c) sperm transfer mechanism play a role in the reproductive isolation of these two species.

Six amide alkaloids of Piper guineense were tested for antifeedant activity against fifth instar larvae of Chilo partellus in choice assays. These amides include piperine, Δα, β-dihydropiperine, wisanine, Δα, β-dihydrowisanine, trichostachine and N-isobutyl-trans-2-trans-4-eicosadienamide. Piperine and its dihydrosaturated derivative exhibited the most potentantifeedant activity. Δα, β-dihydrowisanine and trichostachine were intermediate in activity followed by wisanine. The N-isobutyl derivative was the least active. These results suggest that the presence of a methylenedioxybenzene and an alicyclic amide group in the compound may be crucial for high antifeedant activity.

The haemolymph of the tsetse, Glossina morsitans morsitans, contains a low molecular weight protein of very high density (1.29 g/mi). The protein was detected in the haemolymph during all developmental stages of the insect. Purification of the protein was achieved by a combination of density gradient ultracentrifugation and repeated gel permeation chromatography. Electrophoresis under non-denaturing and denaturing conditions showed the protein to be a single polypeptide chain (M,˜23,000). Amino acid analysis revealed a relatively high content of the acidic amino acids as well as serine and glycine. The protein contained lipids as shown by Sudan Black staining but was nonglycosylated. Using rabbit antiserum against the isolated protein in immunodiffusion and immunoblotting experiments, no cross-reactivity was detected with haemolymph samples from insects representing six orders. Although the function of the protein remains unknown, its uniqueness to Glossina suggests that it may have a role in the physiology of this insect.

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.

Based on a semi-synthetic diet, a standard rearing method for the cotton bollworm, Hetiothis armigera Hübner, is described. The diet is composed of chickpea (Cicer arietinum) flour, yeast powder, sucrose, ascorbic acid, cholesterol, choiine chloride, wheat germ oil, vitamin mixture and a combination of preservatives. A plastic container for individual rearing of the cannibalistic larvae and a cage for mating of adult moths are described. After inoculation with the neonate larvae, development of the different stages was synchronouson this diet. The larval and pupal development period was 14.3 ± 1.2 and 11.7 ± 0.82 days, respectively. Females reared on this diet produced an average of 2000 eggs. Adult longevity was 22 days. The female moths retained their oviposition rhythm even after 3 years of laboratory rearing. A method for introduction of wild populations into the laboratory culture is discussed. The reliability of the technique was checked by monitoring the insects' performance for at least 25 generations.

Amblyomma hebraeum differs from many ixodid tick species in that it is not susceptible to the direct effects of the host immune response. All stages of the life cycle are able to feed repeatedly on laboratory hosts and show no progressive declines in engorged weight. However, on cattle there are declines in the yield of engorged adult females over time, as animals become sensitized to the tick and grooming increases. In the field zebu, Bos indicus and sanga, B. indicus x B. taurus breeds of cattle become less heavily infested than B. taurus breeds. The apparent resistance of zebu and sanga breeds is the result of learned tick avoidance behaviour, skin sensitivity and the ability to dislodge ticks prior to attachment as well as grooming ability. Among other Amblyomma spp., the feeding of A. americanum is adversely affected by acquired host immunity, while that of A. variegatum is generally unaffected.

The effect of pod angle on the resistance of cowpea, Vigna unguiculata (L.) Walp. to the legume pod borer, Maruca testulalis Geyer, was investigated under field conditions at the International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria, using two cowpea cultivars: IT82D-716 (susceptible to borer damage) and TVu 946 (resistant to borer damage). Three different pod angles were used In the study — a normal angle, a decreased angle and an increased angle. Negative and highly significant (P < 0.01) relationships were found between pod angle and per cent pod damage, as well as the seed damage Index In the two cowpea cultivars. Pods with wide angles (≥ 89°) were damaged on only one and rarely on both pods. Apart from biochemical and other bio-physical factors, selection and breeding for wide pod angle is suggested as a strategy for reducing M. testulalis damage to cowpea pods.

A comprehensive review of the acquisition of resistance in bovine and laboratory hosts as a result of natural infestation with various species of ticks is undertaken. In this review I discuss the biological aspects of the expression of resistance, deal with acquisition of resistance to ticks by bovine and laboratory animals, give details on the environmental and physiological factors which affect the resistance and explain the mechanisms of resistance in both bovine and laboratory animals. I also deal with the relationships between ticks and their bovine hosts and emphasize the difference in the acquired resistance of individuals in the breed as well as the negative correlation between the decrease in mean weight of the ticks and the increase in the levels of globulins in the serum of the different hosts.

Aspects of cross resistance by hosts to different species of ticks are also discussed in this review.

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.

Surveys were conducted in 1981, 1983 and 1984 across the island of Puerto Rico to determine the effects of patch characteristics of the tropical herbaceous legume, Crotalaria pallida Ait. on the herbivore and its parasitoids. The mean number of flower racemes per plant and mature pods per raceme varied from year to year and appeared to be influenced by rainfall patterns, but were independent of patch size or plant density. Low larval parasitism was also observed during dry seasons. Proportion of plant patches colonized by Etiella zinckenella was smallest during dry seasons. Local extinction of C. pallida patches was found commonly, with a 77.4% extinction rate during a 6-month period. Patch extinction, which was caused mainly by human activity, was independent of patch size.

Pods of C. pallida within patches were inspected for lima bean pod borer, E. zinckenella (Lepidoptera: Phycitidae) injury. The number of pods bored per mature raceme, and the per cent of bored pods were positively correlated with the number of host-plants per patch and the (surface) area of the patch. No correlation was found between per cent parasitism and pod borer larval density. However, per cent parasitism was influenced directly by C. pallida plant density and patch surface area. Given the transient nature of C. pallida patches and the changes that occur over a season, these positive responses of parasitoids to plant density and patch surface area are important components for their successful exploitation of larval hosts.