Cellular and humoral immune responses against arthropod vector antigens in invertebrate hosts affect vector physiology and significantly modulate the transmission of pathogens. This phenomenon may be the basis for novel methods of disease control based on immunization against arthropod antigens. Current research in this field is briefly reviewed.

The importance of the gram pod borer, Helicoverpa (=Heliothis) armigera (Hiibner) and the earhead bug, Calocoris angustatus Lethierry in the sorghum panicle was assessed. Gram pod borer consumed 2. 364 g of dough stage grains from fourth instar to pupation. A total of 74. 50 grains were damaged during the complete larval period. Grain loss was 14. 32 and 29. 42 g respectively when 50 and 100 nymphs per panicle were confined. When the two species occurred together grain loss was more than the sum of the loss due to each species alone.

Five mutants for seed coat colour from the faba bean, Viciafaba L. variety BF 2/2 (Beladi) were tested qualitatively and quantitatively for tannin content. The susceptibility of the mutants to Bruchidius incarnatus (Boh.) and Callosobruchus maculatus (F.) was also evaluated. All seed coats contained tannins (0.75–3.75%). The darker the colour the lower the tannin content. Cotyledons with testas removed were devoid of tannins. The thickness of the seed coats ranged from 0.146–0.155 mm, however, differences among mutants were not significant. Faba seeds were more suitable for the multiplication of B. incarnatus than C. maculatus. The poor performance of the latter was manifested as low fecundity, high mortality and longer developmental period. It was concluded that selection for white coloured faba seeds should not be discouraged on the basis of its assumed susceptibility to bruchids.

Chromosomal inversion polymorphism was investigated in samples of Anopheles gambiae sensu lato collected from different localities of Tanzania. An. merus was found monomorphic, while two widespread inversion polymorphisms were recorded in both An. gambiae sensu stricto (2Rb/+ and 2La/+) and An. arabiensis (2Rb/+ and 3Ra/+). Two additional polymorphic inversions (2 Rbr and 2Rq), generally associated, were observed in An. arabiensis from the Rift Valley. Observed karyotype frequencies were in agreement with those expected according to the Hardy-Weinberg equilibrium suggesting conditions of panmixia in both An. gambiae s.s. and An. arabiensis in the studied areas.

The specific activity of ATPase in whole body and mitochondrial homogenates declined significantly with age and on propyl gallate (25 μg/ml standard medium) feeding in both the sexes of Zaprionus paravittiger reared at 26 ± 2°C. Maximum activity was observed during the reproductive period.

A pheromone trap network was used to study the temporal and spatial variations in the abundance of the pod borer, Helicoverpa (= Heliothis) armigera (Hubner) in India. The pattern of pheromone trap catches of Helicoverpa armigera was similar within any given agroclimatic zone but there were also obvious changes with latitude in patterns of trap catches. The catches were generally higher and had more sharply defined peaks, at northern locations than at southern locations. The catches at the eastern locations were lower than those elsewhere. The practical applications of this information for pest control are discussed.

Nineteen accessions from seven Lycopersicon species were bioassayed for their resistance to Heliothis armigera (Hübner) (Lepidoptera: Noctuidae) in laboratory tests at 29 ± 1°C and 65 ± 2% r.h. Data on larval developmental duration (days), survival (%) and pupal weights (mg) revealed that maximum resistance to H. armigera occurred in accessions of L. hirsutum f. glabratum and L. hirsutum. When the larvae were fed on the foliage of PI 134417 and PI 126449 accessions (L. hirsutum f. glabratum), the developmental time was longer, and survival rate and pupal weights were lower than when the larvae were fed on cultivars of L. esculentum. Rearing of H. armigera larvae through third instar is sufficient to evaluate the resistance of wild tomato foliage since most of the larval mortality occurs prior to this stage. Accessions of L. peruvianum, L. chilense, L. cheesmanii and L. pimpinellifolium proved less resistant than L. hirsutum f. glabratum and L. hirsutum but significantly more resistant than L. esculentum. Thus, among the various Lycopersicon spp. bioassayed, accessions of L. hirsutum f. glabratum seem to have most potential for breeding H. armigera resistant cultivars.

Catantops spissus spissus were reared in groups of 10 using Calapogonium mucunoides, Zea mays, Elaeis guineensis and Manihot esculenta separately. The proximate compositions of these various food types were analysed and energy contents calculated. This was to establish how food types can influence the rate of development of the insects.

The results showed that insects reared on C. mucunoides and Z. mays had the fastest maturing period in days while insects reared on E. guineensis and M. esculenta developed much later. The rate of food consumption could not be related directly to the amounts of individual nutrients nor the total energy content of the food. On the other hand the rate of development of the insect appeared to be directly related to total energy derivable from the overall food consumed. In addition, differences in the rate of development were noticed at the various instar stages. This was also related to the amount of energy consumed from the food types at the particular instar stage.

Studies were conducted on components of resistance to sorghum midge on four resistant (DJ 6514, AF 28, TAM 2566 and IS 15107) and two susceptible (CSH 1 and Swarna) cultivars. Short floral parts, faster rate of grain development and high tannin content of grain were apparently associated with resistance to sorghum midge, Contarinia sorghicola Coq. Genotypic and phenotypic correlations between the factors associated with resistance to sorghum midge were in the same direction (positive or negative) as their association with resistance to this insect. Glume g2, lemma 12, anther and lodicule length, rate of grain development based on dry weight (except oviposition), and tannin content of mature grain showed correlation and path coefficients (direct effects) in the same direction. These characters can serve as a useful criteria to select for resistance to sorghum midge.

Using D2 and canonical cluster analysis, AF 28 was found to be distinct from other sources of midge resistance. However, based on larvae/100 florets, DJ 6514 was also placed distantly from TAM 2566 and IS 15107. Based on egg numbers, adults emerged and grain damage, DJ 6514 was grouped with TAM 2566 and IS 15107. Susceptible hybrid check, CSH 1 was generally placed distantly from the self pollinated susceptible variety, Swarna. These results indicate that the sources of resistance to sorghum midge are diverse, and there is a distinct possibility of increasing the levels and diversity of resistance to this insect.

Four species in the genus Amblyseius Berlese are reported from Tanzania, A. serengati sp.n., A. fustis Pritchard and Baker, A. largoensis (Muma) and A. sawaga Pritchard & Baker. Descriptions and comparisons with similar species are provided for the new species.

Apanteles taragamae is a major parasite of Diaphania indica, a serious peston cultivated cucurbits. Variations in the parasitism of D. indica infesting different cucurbits in thefield were observed. Four cucurbits viz: ivy gourd, cucumber, bitter gourd and musk melon were screened to identify the host plant(s) favourable to A. taragamae. Maximum parasitism was recorded on bitter gourd andivy gourd. These two cucurbits were favoured over musk melon and cucumber when leaf hairness was examined. Both ivy gourd and bitter gourd had smoother leaves than cucumber or musk melon and parasitism of larvae on smooth leaf plants was greater. However, on the basis of parasite development on the four cucurbit reared host larvae, it was concluded that D. indica's preference for bitter gourd and ivy gourd was due to the influence of the host habitat (leaf hairness) and not due to physiological factors.

Immune resistance to infestation by the brown ear tick, Rhipicephalus appendiculatus Neumann, was induced in rabbits by repeated tick feeding. Antibodies from the rabbits resistant to ticks were purified and used to isolate tick midgut antigens. Purified immunoglobulin G (IgGs) from rabbits immune to tick infestations demonstrated, by immunoblotting, nine protein subunits with molecular weights ranging from 12,000 to 92,000 daltons. Immuno-adsorption studies revealed an aggregated native protein with a molecular weight greater than 500,000 daltons as resolved by polyacrylamide gel electrophoresis (PAGE). Sodium dodecyl sulphate (SDS)-PAGE of this protein molecule revealed the presence of 14 protein subunits similar to some of those detected by the immunoblots. Their molecular weights ranged from 14,000 to 165,000 daltons. Sera from rabbits immunized with the 500,000 dalton molecule formed a weak precipitating arc in the immunodiffusion test, confirming its immunogenicity. The reproductive potential of ticks fed on rabbits immunized with the purified protein molecule was slightly affected compared to controls. The protein molecule also had the capacity to induce immediate and delayed type skin reactions when injected into rabbits resistant to adult R. appendiculatus, as opposed to control tick-naive rabbits.