The effect of mixed cropping cow pea with maize on general predators' abundance and their influence on population density of Megalurothrips sjostedti (Trybom) on cowpeas was investigated in the field and in exclusion cages. Populations of predatory ladybird beetles, Orius sp. and earwigs (Dermaptera) were not significantly influenced by mixed cropping. The density of spiders, however, was significantly higher in the cowpea sole crop than in the cowpea/maize mixture. The population density of M. sjostedti was significantly less in the cowpea/maize mixture than in cowpea sole crop, both inside cages, where predators were excluded, and outside. We concluded that this reduced population density was not the result of enhanced predators’ population in the mixture.

The effects of temperature on the development of Orius albidipennis (Reuter) (Hemiptera: Anthocoridae), reared on its prey, Megalurothrips sjostedti (Trybom) (Thysanoptera: Thripidae), were studied in the laboratory. Nymphal mortality was 87, 48 and 38 % at 20, 25 and 30 °C, respectively. With the exception of first-instar nymphs, percentage mortality was lowest at 25 °C. Pre-oviposition period and longevity decreased with an increase in temperature. Mean daily and total fecundity were 2.1 and 76.4 respectively at 25 CC. The mean developmental period from oviposition to adult eclosion was 27.7, 14.1 and 10.9 days at 20, 25 and 30 °C respectively. There was a linear relationship between temperature and developmental rate (1/day) of O. albidipennis. Lower thermal thresholds were 13.8, 13.5, 12.7, 15.0, 13.8 and 12.5 °C for eggs and nymphal stages 1 to 5, respectively, with the corresponding average degree-day requirement of 46.9, 42.6, 33.3, 29.2, 26.1 and 51.4 days, respectively. The implications of these results for biological control of thrips are discussed.

The functional response of fourth instars, adult males and females of the sevenspotted lady beetle, Coccinella septempunctata Linnaeus (Coleoptera: Coccinellidae), was studied at different densities of aphid, Lipaphis erysimi (Kaltenbach) (Homoptera: Aphididae). The maximum prey consumption was recorded for fourth instars at the highest prey density (800) and the minimum for the male lady beetle at the lowest prey density (25). The prey consumption by the predatory stages of the lady beetle was directly and the percent prey consumption inversely proportional to prey density. Prey handling time decreased with increasing prey density. Regression analysis showed a linear relationship between the log number of prey exposed for predation and prey consumed. The predatory efficiency of the predator stages was directly proportional to prey density, indicating a Holling Type II functional response.

We studied the distribution of wild Mediterranean fruit flies, Ceratias capitata (Diptera: Tephritidae) in different environments of trimedlure-baited Jackson traps during high fall season populations in Southern Egypt. We found that 98% of females attracted to within aim radius of standard trimedlure (TML)-baited Jackson traps remained on the surrounding foliage without approaching the trap. Also about 30 % of males aggregated there, calling and competing for matings with approaching females. The closest mating occurred 25 cm from a standard trap. The nearest lek formation away from a trap was observed at a distance of 2 m on the same trap tree. The highest captures of males were recorded in the morning after male calling on the foliage reached its daily peak. Jackson traps baited with both protein hydrolyzate and TML on cotton wicks caught as many males, but significantly more females than traps with TML only.

A systematic account of the lepidopterous cereal stemborers in Africa is presented. The identification and distribution of the economically important species is discussed. Systematic problems are pointed out.

The life cycle of Cathartus quadricollis (Guerin-Meneville) was studied under ambient laboratory condition on maize, sorghum, wheat, cowpea and melon. Egg hatchability was found to be 95.5% with an incubation period of 3–7 days. Five larval instars were recorded based on head-capsule width measurements. The growth ratio of the head-capsule width ranged from 1.05–1.20 with a grand mean of 1.12. This range falls within the acceptable range in Dyar's rule. The mean growth rate of C. quadricollis after 2 weeks of rearing on maize, sorghum, melon, wheat and cowpea, ranged from 22.4 to 1.6. While the mean developmental periods of C. quadricollis on the selected food media ranged from 18.80 days on cut maize to 30.70 days on cut cowpea.

This paper describes the immature stages of the striped caterpillar Epicerura pulverulenta Hampson, a notodontid defoliator of combretaceous trees, viz., Terminalia ivorensis, T. superba, T. catappa and Anogeissus leiocarpus. The structure and chaetotaxy of the mature (fifth stage) larva is described in detail with illustrations to aid easy field identification of the moth.

The effectiveness of aqueous neem leaf and seed extracts for the control of the diamondback moth (DBM), Plutella xylostella (Linnaeus) (Lepidoptera: Plutellidae) on cabbage was evaluated in field tests at Chokwe, Mozambique and compared with parallel dimethoate + cypermethrin treatments. All the neem treatments recorded significantly higher yield of marketable heads of cabbage and significantly better control of diamondback moth than the commonly used mixture of pyrethroids or the untreated control. The neem seed extracts provided the best control of DBM. The possibility of using neem extracts as part of an integrated pest management system for DBM control in smallholder farms is discussed.

The use of surfactants and their blends to improve the penetration of two insect growth regulators (IGRs; hydroprene and R-20458) into wheat kernels was investigated. It was found that formulation of IGRs with a surfactant, Tween-85 (polyoxyethylene trioleate), increased mortality and/or effectiveness of the IGRs. Formulation of hydroprene with a blend of Span-80 (sorbitan monooleate) with Tween-80 (polyoxyethylene monooleate) produced results comparable to those by hydroprene with Tween-85. However, formulations of IGRs with surfactants with high or low hydrophile-lipophile balance (HLB), failed to provide suitable control of the weevil, probably due to the type of emulsions formed. The same results were obtained with hydroprene formulations with blends of Spans and Tweens, even though their HLBs were close to that of Tween-85. Residual half-life for hydroprene was about three months; formulations with Tween-85 or a blend of Span-80 did not enhance the residual activity for hydroprene in wheat.

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.

By employing histological techniques, it was possible to identify 11 stages of oocyte development in adult female Sarcophaga tibialis (Diptera: Sarcophagidae). Stages 1–4 were represented by the differentiation of the oocyte and the acquisition of the follicular envelope. Stages 5–9 were characterized by a considerable growth of the oocyte which occurred due to an enormous deposition of yolk in the cytoplasm, while the follicle cells were typified by large intercellular spaces. Descriptions are given of the follicle cell degeneration during stages 10 and 11, which end with membrane formation around the mature egg.

Biological and morphometric studies of the different stages of Lucilia caesar, were carried out using three rearing media prepared from local materials as the test media, and the standard Snyder's medium as control. The materials for the test media were: (i) Garri, soybeans, palmwine and liver (GSPL), (ii) Garri, soybeansand palmwine (GSP) and (iii) Pap, nono, cabbage and liver (PNCL). The Snyder's medium consists of milk, yeast and bacto agar (M Y A). There was no significant difference in the duration of larval instars and adult emergence for the blowflies reared in the standard, PNCLand GSPL media. For blowflies reared in GSP, duration of larval and adult stages was prolonged by about 48 hr and 5 days respectively, when compared with the flies reared from the other three media. The average length and width of each larval stage reared from the four media were not significantly different. Morphometrics of the adults showed that those reared from the GSPL and control media were longer, heavier, and laid significantly more eggs per female than adults reared from PNCL and GSP media. The GSPL medium was considered to be the most suitable alternative to MYA.

Commercial cotton growing in the Sudan dates from 1867. At present, about 400,000 ha of various cotton cultivars are grown under different irrigation systems. The production of this main cash crop has been faced with a multitude of entomological and pathological problems, some of which were tackled through the adoption of specific cultural practices or enforcement of legislative regulations.

When cotton treatment with synthetic organic insecticides was initiated in the mid 1940s against Empoasca lybica de Berg, the impressive preliminary results have encouraged over-reliance on chemical control at the expense of other measures. This rather limited approach of control strategy has contributed partially to the appearance of new pests in damaging levels e.g. Heliothis armigera (Hbn.), Bemisia tabaci (Genn), Aphis gossypii (Glov) and Spodoptera littoralis. The principal measure for their control is insecticide application.

The cost of crop protection soared to ten-fold during the last 20 years. The annual number of sprays applied to cotton increased from one to seven sprays. To overcome the ever increasing use and high costs of pesticides on cotton growing, the Agricultural Research Corporation undertook intensive research programmes to find answers to major crop protection problems. Since 1978 researchers are directing their efforts towards the development and implementation of integrated pest management strategies to include cultural and legislative measures, as well as the use of more selective insecticides.

Selected aspects of ecological interactions with ticks, tick-borne diseases and their hosts are discussed in relation to Integrated Tick Management, The needs to preserve tick-borne disease enzootic stability and to ensure the economic justification for any interventions were emphasized.

Field studies were conducted to characterise the effects of infestations by adult and nymphal stages of cowpea aphid, Aphis craccivora Koch, on the growth and yield of cowpea, Vigna unguiculata (L.) Walp. Seedling, flowering, and podding stage plants of aphid-resistant (cv. ICV-12) and aphid-susceptible (cv. ICV-1) cowpea cultivars were used in the studies. Four treatments (consisting of infestations with adult and nymphal aphids, caged controls and uncaged controls) were administered on plants for 22 days post-treatment. Eight parameters of crop success were measured: extended leaf heights (ELH); plant mortality; incidence of sooty mould; incidence and abundance of natural enemy species; crop growth parameters (net assimilation rate, [NAR] in g/ dm2/day, and crop growth rate [CGR] in g/dm2 land surface/day); and plant yields (seeds per pod, weight per seed). Data were analysed using analysis of variance (ANOVA), orthogonal contrasts and 95% confidence intervals (C.I.). There were no significant (P > 0.05) differences between adult and nymphal infestations or between caged and uncaged controls, so the respective sets of data were combined for comparisons of aphid infestations with control treatments. Infestations caused severe plant stunting and other growth deformities, drastic yield reductions, higher plant mortality, greater incidence of natural enemies and abundance of Cheilomenes spp. on cv. ICV-1 than on cv. ICV-12, and on infested and uninfested plants. Aphid infestations did not significantly affect the incidence of sooty mould on plants of cv. ICV-12 or cv. ICV-1.

Stability of resistance to corn planthopper, Peregrinus maid is (Ashmead), was studied over three plant growth stages in 56 sorghum germplasm accessions. Genotype x stage interactions were significant. Plant age exerted a profound influence on the rate of oviposition, establishment of nymph, macropterous and brachypterous adult populations and plant damage. Resistance to corn planthopper was stable over three growth stages in IS 18557, IS 18677 and PJ 8K(R), which also supported low colonization of nymph and adult populations; IS 12308 was unstable due to high deviation. Significantly low rate of oviposition on resistant as compared to susceptible genotypes and the positive and significant correlation between oviposition and plant damage illustrated that antixenosis for oviposition is the primary mechanism of resistance. As a consequence the genotypes preferred for oviposition showed susceptibility due to higher plant damage. Establishment of nymphs was affected on the genotypes, IS 1054, IS 1082, IS 2194, IS 3992, IS 12308, IS 18676 and IS 19349 which may be due to the factors involved either in reduced hatchability of eggs and/or deterrence or poor feeding preference of nymphs.

Host searching, slit making, egg deposition and protection are distinct sequences of one event, which lead to oviposition on the lower surface of rice leaves by the rice hispa Dicladispa armigera (Olivier). Females spent an average of 8.05±1.35 min in selecting an oviposition site, 6.40±0.25 min in preparing a triangular slit, and 1.17±0.07 min in laying and protecting a single egg. An egg measuring 0.85×0.42 mm in size was partially inserted inside a slit of 1.95×0.84 mm. The female exhibited ovipositional preference among the leaves of a rice plant, as 67.5% of eggs were deposited in the first leaf. On the first, second and third leaf, the female deposited her eggs mostly in the middle part of the leaf blade, avoiding the area between 4.15–4.89 cm from the tip and 12.72–14.25 cm from the base of the leaf.

Neuroendocrine mechanism involved in pupal colour dimorphism in Papilio xuthus L. has been studied using ultrastructural techniques. The browning hormone in the form of neurosecretory material is secreted in the brain during the larval stage and transported to the axonal endings in the prothoracic ganglion, irrespective of the colour of the future pupa. If larvae select for pupation environmental conditions that are conducive for the formation of a brown pupa, release of the browning hormone occurs in the middle of the prepupal stage. No release occurs in larvae that have selected environmental conditions that favour the formation of green pupae. It is suggested that the brain, having integrated and interpreted the environmental conditions selected by the larva for pupation, gives the order to release the browning hormone. Such an order is conveyed via neural path from the brain to either the prothoracic ganglion, or some still unknown neurohaemal organ associated with it, from which release then takes place.

Experiments were carried out to determine the factors that influence the feeding behaviour of Culex tigripes, a mosquito whose larvae are predators of other mosquito larvae. The results indicated that the efficiency of predatory activities of Cx tigripes larvae increased as they developed from 1st to 4th instar with regard to the number of mosquito prey larvae they consumed in a given period of time. Fourth instars of Cx tigripes are the most voracious of all the stages and are better adapted for catching and consuming all stages of mosquito larvae. The mean number of mosquito larvae consumed in 24 hours increased with increasing prey density. When offered a mixture of different prey species and larval stages, Cx tigripes larvae consistently selected 4th instars of mosquitoes over pupae and preferred Aedes aegypti larvae to the larvae of Cx quinquefasciatus and Anopheles gambiae. Prey size, density and mobility were also found to influence prey selection by Cx tigripes.

The total number of eggs laid by Callosobruchus rhodesianus (Pic.) and Callosobruchus maculatus (F.) females in the presence of single and mixed species populations of males at different densities were counted. Increasing male density significantly reduced the realised fecundity of C. maculatus but not C. rhodesianus females. In the presence of C. maculatus males, however, the number of eggs laid by C. rhodesianus was greatly reduced. The reduction in egg laying and observations on mating behaviour indicates direct physical interference between weevils and competition for mates. An adequate number of beans were provided so competition for oviposition sites by females was unlikely. The ability of C. maculatus to inhibit oviposition of C. rhodesianus is suggested as one reason for its superiority over the latter when the two species compete for limited resources.