Insect Science and its Application.

Progress in Protozoology. Proceedings of the VIIth International Congress of Protozoology. Volume 7 Number 3.

Due to an oversight the Editor regrets that the title of the Special Issue, Volume 7 Number 3, should have read; “Progress in Protozoology” not “Progress in Entomology.”

The shootfly, Atherigona soccata Rondani, is a major seedling pest of sorghum in many areas of tropical Asia, Africa and Mediterranean Europe. A chronological review of the progress made in various programmes on the screening techniques (natural and artificial) with artificial diets, sources, stability and mechanisms of resistance, bases (physico-morphological and biochemical factors) of resistance, inheritance and breeding for resistance is made. Many resistant varieties have been identified and sources of resistance utilized in breeding programmes to transfer resistance in high yielding background are listed. In addition, the glossy and trichome traits identified is sorghum cultivars are also reported. Glossy leaf surface and trichomes are frequently associated with shootfly resistance.

Female ticks of Ornithodoros porcinus porcinus undergo a series of adult moults when fed on blood containing ecdysteroids. The supermoulted ticks are bigger, ingest larger blood meals and lay more eggs than normal females. However, their rate of conversion of blood into eggs and their oxygen uptake are reduced in comparison to normal ticks. Their ability to resorb the rehydrated salt crystals is impaired. They are unable to shed the cuticle of the Géne's organ area leaving the organ constantly protruding, thus making the ticks vulnerable to dehydration. These factors are probably responsible for the very high mortality and the failure of most of the ticks to moult at the third supermoulting cycle.

Papers on tolerance of alfalfa, barley, sorghum, corn, rice, wheat, cotton, vegetables and tea to insects are reviewed. Research methods used in identifying tolerant cultivars and the role of tolerance, as one of the three mechanisms of resistance, are discussed.

Initial findings are reported from a study of Exhyalanthrax spp. (Diptera, Bombyliidae) and Chrestomutilla spp. (Hymenoptera, Mutillidae) parasitic on tsetse pupae, with a view to their use as control agents. The behaviour of bombyliids in the field and in cages is described and related to problems encountered in laboratory rearing. Limited progress is also reported in the breeding of mutillids. Prospects for the application of pupal parasites in biological and integrated control of tsetse are discussed.

The cell cortex of a ciliated protozoan contains most of the structure that defines the shape and pattern of the organism. The ciliate cell cortex is composed of both cytoskeletal and membranous components. While the assembly of the cytoskeleton is believed to account for the major part of the development of shape and pattern in this cell (as in all eukaryotic cells), the contribution of membranes to the development of cellular architecture in ciliates is poorly understood. Also, how the cortical membranes are assembled and how this assembly is coordinated with cytoskeletal assembly are virtually unknown. Furthermore, membranes have several unique properties which could be useful in the storage and utilization of blueprints for cellular architecture. Freeze-fracture and freeze-etch electron microscopy provide ways to characterize the molecular architecture and assembly of membranes during development. Efforts are being made to apply these methods to an analysis of morphogenesis and ciliogenesis in Tetrahymena. The results of these studies ar summarized and their possible implications regarding the role of membranes in ciliate morphogenesis are discussed.

Urine from the buffalo, Syncerus caffer, a natural host of the tsetse, has been shown previously to be a potent olfactory attractant for tsetse in the field. The attractant compounds have been found to be extractable into dichloromethane. Fractionation of the extracts by liquid flash chromatography yielded four fractions one of which gave a seven-fold increase in trap catches in the field compared to the control traps. Gas Chromatographie and gas chromatography–mass spectrometric analysis of this fraction revealed the presence of seven simple phenols including phenol itself.

A laboratory study of the biology of Corcyra cephalonica (Staint.) was made at 30°C and 70% r.h. on sorghum. The number of eggs laid per female, oviposition period, development time and survival from egg to adult were determined. The data were used to estimate the finite rate of increase and the intrinsic rate of natural increase of the moth. For the finite rate of increase (λ) the estimated value was 18 per lunar month, corresponding to an intrinsic rate of natural increase (r) of 2.9. The results are compared with published data and it is concluded that the pest potential of C. cephalonica has been, hitherto, underestimated.

Three polyvinyl chloride (PVC) formulations of malathion were prepared and tested as controlled-release formulations against mosquito larvae of Culex pipiens L. Non-expanded formulations gave effective control, with 100% larval mortalities, for 23–51 days, followed by expanded (16–33 days) and foamed (14–27 days) formulations. The results indicate that increasing the percentage of active ingredient in the present formulations increased their effective control against mosquito larvae for longer periods.

Larval treatments with these formulations of malathion led apart from lethal action to a decrease in the reproductive potential and in longevity of mosquito adults which survived from these treatments.

Breeding biology of oil palm weevil, Temnoschoita quadrimaculata Gly., was studied. Females lay small, whitish and cylindrical eggs singly in cut wounds made on the fronds and trunk of oil palm, Elaeis guineensis Jacq. The larvae were found to feed voraciously in the fresh and dead tissues of the palm fronds and trunk. The weevil has six overlapping generations. Unmated females were observed to have longer pre-oviposition period, laid fewer eggs and lived longer than the mated ones. Durations of the immature stages of the weevil are studied. Natural enemies and alternate host plants of the pest are given.

The pearl millet, Pennisetum americanum L., a major food crop in the Sahel, is regularly attacked by a complex of spike worms, of which Raghuva albipunctella De Joannis (Noctuidae: Lepidoptera) is the most common and abundant species. The research on taxonomy, economic importance, biology and ecology of spike worm and control measures used to suppress its populations is reviewed from 1972 (period of its first outbreak) to 1984. Further studies are proposed to develop a viable pest management strategy which would be effective, practical, economical and easily adopted by the farmers. The present paper also discusses the difficulties and possibilities of such approach in relation to subsistence farming systems.

Injection of antiserum prepared against accessory reproductive gland (ARG) secretions of the male desert locust, Schistocerca gregaria, disrupted the normal growth and function of the ARG complex in sexually maturing adults. Male locusts were injected with either antiserum or normal guinea-pig serum on days 3, 7 and 10 after adult ecdysis. When the injection of ARG antiserum began as early as day 3 of adult development a marked inhibition of ARG growth was accompanied by the suppression of other characteristics of sexual maturation (yellow body coloration and mating behaviour). Inhibition of ARG growth, while significant, was less pronounced when antiserum injections began on day 7 of adult development, and the injected males did not exhibit normal mating behaviour when placed with virgin females. When single antiserum injections were administered on day 10 of adult development, the males still attained their yellow body coloration by day 19 and copulated normally with virgin females, although their ARGs were only equivalent in size to those 13-day-old males.

Nosema sp. naturally occurred in both Spodoptera littoralis (Boisd.) and S. exigua (Hübner) laboratory colonies in Alexandria, Egypt (since November 1984). It was responsible for the dramatic suppression of their laboratory populations. Both young (3-day-old) and old (9-day-old) larvae of S. littoralis were susceptible to Nosema sp. However, the pathogen was more effective against the young larvae, especially at high doses, than the old ones. The estimated LC50 was 4.0 × 107 spores'ml, for 3-day-old larvae. The slope value was low (1.2) as typical of protozoan insect pathogens. Heavily infected 9-day-old larvae tended to die as larvae; while less infected ones either pupate or produce larval-pupal intermediate forms (12–23%). The developmental period of both infected larvae and pupae was increased by 4–6 and 3–5 days, respectively. The number of infected insects that reached the adult stage was decreased as the concentration of Nosema sp. spores was increased. Furthermore, infection was shown to reduce adult longevity and fecundity, and viability of the eggs. Larval faecal pellets harboured large numbers of viable spores. Transovum transmission of infection occurred. Two dipterous species, Culex pipiens and Aedes aegypti, were not susceptible to Nosema sp.

Nightly catches of Scirpophaga nivella (F.) in light traps in rice plots in West Bengal, India, showed two discrete peaks of abundance in each trap-year corresponding to congenial weather and abundance of summer (mid-March-mid-June) and autumn (mid-July-mid-November) rice plants. Estimated generation times showed many overlapping generations in each trap a year. Variations in summer catches were significantly correlated (P < 0.01–0.05) with maximum temperature and minimum relative humidity of the day, and minimum temperature and wind speed of the night; whereas those in autumn catches were significantly associated with maximum temperature and minimum relative humidity of the night (P < 0.01–0.05). Autumn crops had more infestations, and sustained greater larval density than summer ones. Females were twice as heavy as males (2.1:1) and adults were heavier in October than in May. Catches of immature and mature females were consistently maximum at full moon and new moon, respectively.

The prospects for vaccine development have been transformed by the advent of hybridoma technology for the production of specific monoclonal antibodies and recombinant DNA technology which permits the in vitro expression of genes coding for protective antigens of pathogenic organisms. These techniques are leading to the refinement of existing vaccines and the production of new vaccines against organisms which either cannot be cultured in vitro at all, e.g. hepatitis-B, or can be cultured only on a limited scale, e.g. plasmodial species. The techniques allow for the novel production of both live and dead vaccines. New live vaccines are produced using either site-directed mutagenesis or insertion of genes into hosts such as vaccinia virus, which is a potential carrier of polyvalent vaccines. New subunit vaccines are produced by expression of appropriate genes in E. coli, yeast cells or mammalian cell lines and some, e.g. hepatitis-B surface antigen (HBsAg) are at an advanced stage of development. Recombinant subunit vaccines are also being produced against the sporozoite and blood stages of malaria. Problems, in regard to the development of malaria vaccines, concern the antigenic plasticity of plasmodia and the need to induce both antibody and cell-mediated immunity; nevertheless, the work shows considerable promise of success.

Entomological investigations in Dubai showed that, irrespective of whether they had been fed on water or 10% sugar solution, about 47% of Aedes caspius females matured eggs autogenously during their first ovarian cycle. Several blood-fed females were trapped in cages, and precipitin tests showed that some had fed on birds and camels as well as man.

Absence of autogeny combined with an examination of male terminalia showed that adults of the Culex pipiens complex were in fact Culex quinquefasciatus. The population was unusual because females were not inseminated when kept in cages, and appeared only weakly anthropophagie. CDC light traps and out of door resting cages proved useful in sampling adults. Precipitin tests showed 31.7% to have fed on birds, 7.9% on camels and only 3.2% on humans.

The number of eggs matured by Ae. caspius and Cx. quinquefasciatus were determined, and studies were made on the hatching pattern of Ae. caspius eggs. Larval habitats of Ae. caspius were unusual in having high concentrations of calcium chloride. Breeding places of Cx. quinquefasciatus comprised very polluted waters. Collections of the immature stages allowed the construction of stage-specific age-frequency histograms for both species, and survivorship curves to be plotted.

Twenty-one insecticides were tested for acute toxicity by surface film contact method against the grasshopper, Zonocerus variegatus (L.) in the laboratory. Decamethrin, cypermethrin, lindane o, o-diethyl(p-methyl sulfinyl) p′-phosphorothioate, and dieldrin were highly potent. Moderately potent insecticides were propoxur, bioallethrin, telodrin, isodrin, heptachlor and rotenone. A toxic symptom common to all potent insecticides in the female was the opening and closing of ovipositor valves which remained wide open at death. Five insecticides—dieldrin, telodrin, p, p′-DDT, chlorobenzilate, DMC and chlordimeform induced cannibalism among the treated females.

Coelomomyces indicus was reisolated from six larvae of Anopheles gambiae in Uganda. A crustacean copepod Cyclops sp. was found to be infected (63%). This indicated that the copepod could be an intermediate host for the fungus. All the four instars were highly susceptible to C. indicus but fourth instar Aedes aegypti was fairly susceptible (94.2%), while second instar An. gambiae (100%) and second instar C. fatigans (100%) were the most susceptible.

Laboratory tests were conducted to compare reproductive capacity and longevity of An. gambiae, C. fatigans and Ae. aegypti when infections of C. indicus were induced in each of the different larval instars. Infections of C. indicus sharply reduced the reproductive capacity and longevity of An. gambiae, C. fatigans and Ae. aegypti, regardless of the instar that were exposed and became infected. The reductions were highest when first and second instars were exposed. The tests indicated that introduction of C. indicus into laboratory populations of An. gambiae, C. fatigans and Ae. aegypti consisting of mixed larval instars, could significantly reduce the number and fertility of eggs and thus result in an average reduction of about 65.4% for An. gambiae, about 46.7% for C. fatigans and 58.7% for Ae. aegypti of the F1 progeny from those females that became infected. The importance of these results in biological control is discussed.

Dosage–mortality responses of F1 progeny of treated rice weevils, Sitophilus oryzae, indicated that the weevil is highly tolerant to R-20458. However, the ability of the insect growth regulator (IGR) to suppress F2 progeny production, demonstrated that R-20458 could be used as a protectant for grains.