Nilaparvata lugens (Stål) biotype 1, 2 and 3 populations maintained as stock cultures for several years showed distinct morphological segregation based on multiple discriminant analysis using Wilk's Lambda method. Morphological characters of the rostrum, legs and antennae of both brachypterous and macropterous males and females provided a significant degree of certainty in classifying the three biotypes. The predicted biotype composition of the brown planthopper populations formed separate clusters.

The structure and size of the eggs and layers of eggshells of some ticks of veterinary importance in Nigeria were studied. The ticks included Amblyomma variegatum, Boophilus decoloratus, B. geigyii, Hyalomma impressum, H. impeltatum, H. truncatum and H. rufipes. The embryonic development of the eggs from the day of oviposition to hatching was also studied.

The freshly laid egg was found to possess 10 protuberances, and the biggest of them are the anterior and posterior ones. The eggs of A. variegatum were found to be the longest, and those of H. truncatum the shortest. The eggshell of all the species is two-layered on one lateral side and three-layered on the other; the middle layer originating from the anterior and posterior protuberances. Several phases of embryonic development are described. The major difference between the embryonic development of the eggs of A. variegatum and that of the others is that there are always phases during which the egg becomes canoe-shaped and later folds back to the normal egg shape. Eggs of B. decoloratus occasionally developed this way as well as those of some Hyalomma species when incubated at 37°C. The period of accomplishment of each phase of development was shortened by high temperatures. Observations on the occlusion periods of various types of eggs showed that the very small eggs would not hatch into larvae. The relevance of these observations to field tick control is highlighted, while the necessity of following up these studies with electron microscopic views of some aspects of the results is stressed.

In choice tests with well-established natural trails and glandular extract trails, allopatric populations of Trinervitermes bettonianus Sjöst followed alien colonies' trails with the same degree of motivation as their own trails. The five Trinervitermes spp. tested readily followed each other's trail. Chromatographs of natural trail extracts showed that the main component of the T. bettonianus trail pheromone also occurs in trails of T. gratiosus (and presumably in the other species); this would account for the observed cross-following of trails among these species.

The literature published during 1970–1981 on tsetse ecology is reviewed. The geographical distribution of some species was affected during the drought of early 1970s. New maps of tsetse distribution in Africa and a few national maps have been published. The habitats of several species have been described in detail, particularly atypical habitats in peridomestic situations. Pupal ecology has not held the attention of ecologists so much; however, pupal duration and mortality have been assessed for a few species. Due to the importance of selective application of insecticides, resting sites and resting behaviour have been described in detail. Activity patterns have been correlated with climatic factors and also with sampling methods. Several works on host-seeking behaviour, flight performance and energy metabolism have been described. Host preferences of certain species have been found to be somewhat different from those previously recorded; and new host species have been discovered. Studies on fat and haematin content showed that these metabolites are useful indices of nutritional status to interpret feeding behaviour in relation to population sampling. A tsetse contact sex-pheromone has been discovered and synthetised; and attempts have been made to use it in the field. Studies on sound production by both sexes under various conditions of light and physiological state are in progress. Comparative studies on sampling techniques have received particular attention; several trap devices have been designed and tested to evaluate the reliability of samples. The determination of the age structure of populations has become more relevant to studies on population dynamics. Attempts have been made to calculate the growth rate of populations. Density-dependent factors started being taken into consideration in the assessment of populations. Several methods have been tried out to estimate population size. New pathogens, parasites and predators have been recorded.

Semi-quantitative biochemical analyses by paper chromatography–densitometry and pH determinations of honeydew excreted by Nephotettix virescens (Distant) feeding on rice plants revealed higher free amino compound and sugar concentrations in honeydew excreted on the susceptible variety TN1 than on resistant ASD7 or P203. Furthermore, sap exudates from these three varieties, presumed to be mainly from xylem, as well as honeydew excreted on the resistant varieties were acidic, whereas honeydew from TN1 was predominantly basic. Since phloem sap in herbaceous plants usually gives an alkaline reaction whereas xylem sap is acidic, and because the former contains much higher concentrations of sugars and free amino acids than the latter, the biochemical evidence strongly suggests that Nephotettix virescens is primarily a xylem feeder on the resistant plants tested, but feeds predominantly on phloem sap in susceptible TNI.

The incidence of cuticular lesions on the ventral abdominal integument of the tsetse Glossina pallidipes, G. Brevipalpis and G. austeni was monitored by trapping over 12 months in four localities along the Kenyan coast. Four types of lesions were observed: necrotic pits, necrotic warts, necrotic striations and necrotic discs. Necrotic discs were most prevalent, and up to 30.5% of female tsetse had this type of lesion. The differences in cuticular lesion levels on flies trapped in the dry and wet seasons were not significant. There were no significant differences in the proportions of tsetse with lesions sampled at different sites. Females had a significantly higher proportion of necrotic pits, necrotic warts and necrotic striations than males but the level of necrotic discs on males and females were the same. Histological examination of tissues did not demonstrate any causal association between lesions and infectious microorganisms. There was no correlation between the presence of cuticular lesions and hypertrophy of the salivary glands, a pathology associated with virus-like particles in G. pallidipes.

The virus Rhabdionvirus oryctes Huger was tried against the root and stem borer of the cashew (Anacardium occidentale L.) in Sri Lanka by pouring a virus suspension into the galleries, releasing virus-infected adults and placing virus-mixed sawdust at the base of the infested stem. Results obtained after several surveys showed that the sawdust technique gave more positive results. The establishment and infection of the virus in the beetle population accounted for a reduction in the beetle damage to the tree in certain pockets of the cashew plantation.

Polyacrylamide gel electrophoresis of saliva infected with Trypanosoma brucei showed few, very faint protein bands as compared to 11 bands from clean saliva. If the saliva collected is 6 times the normal amount, infected saliva showed all 11 bands, plus one more. Inositol and galactosamine did not appear in infected saliva. Infected saliva contained sphingomyelin in addition to phosphatidylethano-lamine, phosphatidylinositol and phosphatidyllecithin.

The detection of household infestations of Triatominae in regions endemic for Chagas' disease is a criterion frequently used in the selection of areas, or of individual houses, for treatment in insecticide campaigns as well as for the evaluation of insecticide performance.

Several methods for the detection of domestic infestations with Triatominae were compared: diurnal capture of live bugs with the aid of a flushing-out agent, night-capture without using flushing-out agents and the use of cardboard boxes of the the Gómez-Núñez type. The flushing-out and Gómez-Núñez box methods were found to be equally sensitive, although each gave several houses as uninfested in which infestation was detected by the other method. The night-capture method was slightly more sensitive but was found to be impractical for large-scale surveys. Improvements to the flushing-out method, notably the introduction of a systematic search technique, made it much more sensitive than the Gómez-Núñez box method for both heavily infested houses and for houses 3 months after insecticide treatment.

Coating the inside surfaces of the boxes with adhesive did not increase the sensitivity of this method and, although this can be achieved by leaving the boxes in place for long periods of time, this also limits the value of the information thus obtained as regards the evaluation of insecticides. On the basis of the results presented, the flushing-out method using a systematic search of the house was found to be the most suitable sampling technique, but it is recognized that this method still has limitations.

Noctuid moths within and around the University of Ife campus were collected, using a mercury vapour light trap, from November 1976 to October 1977. In all, 338 individuals comprising 51 species were caught.

The moths were more abundant during the months of January, April, June and September while the lowest number was recorded in March. The calculated index of diversity tended to follow the same pattern as for abundance. The frequency distribution also shows that many more species were represented by two to five individuals than species represented by more than five individuals.

The possible underlying factors for these observations are discussed.

Field-trapped tsetse Glossina pallidipes, G. brevipalpis and G. austeni were dissected and the incidence of hypertrophy of the salivary glands (HSG) recorded. This condition was observed only in G. pallidipes. The highest level of infection (15.6%) was observed in July in one of the trapping sites. Both very young teneral (ovarian category 0a) and very old (ovarian category 7 + 4N) tsetse had greatly enlarged glands. The differences in bi-monthly HSG incidence for the five trapping sites were statistically significant. The level of infection in males and females did not show significant differences.

At intervals of 2 months over 1 year, 64 royal cells were removed from mounds of Macrotermes michaelseni to find out whether a new royal pair was produced. In five mounds replacement reproductives were found. Young reproductives from incipient laboratory colonies were never accepted as replacements if they were introduced after the removal of the primary reproductives. One out of 10 royal pairs was accepted if the royal cell was introduced immediately after removal of the original one, and three out of 10 survived if the royal cell was introduced 1 week after the removal of the original one.

Replacement reproductives were only produced when nymphs or alates were in the nest at the time the primary reproductives were removed. It was not possible to find out at what time after the removal a new royal pair was accepted but measurements of the replacement queens showed that they can become fully physogastric within 7 months.

The effects of virginity on feeding and milk-gland (MG) activity were investigated in 4-week-old virgin females of Glossina austeni. The flies take in smaller but constant amount of blood roughly equivalent to their own weight during each feed. This syndrome of feeding to a constant weight with time leads to fatbody hypertrophy largely because of decreased metabolic demands due to the absence of a larva. It is suggested that the small blood-meals of virgin females are probably related to the space limitations in their abdomens, and are probably hormone-mediated, possibly operating via the cuticle. The MG of virgin flies is well-differentiated but the cycles of synthetic activity which the distal MG tubules exhibit in mated flies during a pregnancy cycle are not so apparent in virgins. The secretions of this gland are used to nourish the developing larva and if the MG were very active the secretions produced would be lost. It is concluded that in virgin females the blood-meal is reduced in size, probably as a result, at least partly, of a reduction or absence of neurosecretory out-flow related to mating and ovulation, and the products of their blood-meal apparently are diverted not to the MG but to the fatbody for storage. These effects of virginity on blood-meal size, fatbody and MG activity can be reversed at any time by mating.

Data on 2n-numbers of 55 species, belonging to six families of Ghanaian shield-bugs, collected in Southern Ghana, West Africa, are presented. Micrographs and tracings of karyotypes observed for each species are reproduced as figures. Histograms of chromosome numbers of the various families have been constructed and these results, together with the existing information in the literature, are analysed and discussed.

In all, 217 species of Pentatomoidea were found to be known cytologically in the literature. With the present work, the total number of species of shield-bugs where the karyotypes are now known stands at 266.

The following karyotype groups appear to emerge from the study: 14 and 12. Under group 14 is the family Pentatomidae, whilst the families Scutelleridae, Cydnidae and Plataspidae fall under the karyotype group 12. No basic chromosome number can however be cited for the other families of Pentatomoidea, namely the Dinidoridae, Tessaratomidae, Acanthosomatidae and Urostylidae, because the cytological data for each of these are too scanty for any such conclusions to be arrived at. The interrelation of various groups in the superfamily Pentatomoidea is discussed, and the present investigations tend to support the work and conclusions arrived at by morpho-taxonomical studies.

This paper reviews the work which had been done in Nigeria from 1911 to 1981 on several aspects of the biology of Zonocerus variegatus (L.), a variegated grasshopper pest of many food crops. The account covers recent advances in the areas of breeding biology, locomotory and migratory activities, morphometrics, feeding habits, parasitisation, and strategies for effective control of the grasshopper in Nigeria.

Investigations were carried out on the seasonal population fluctuations of the moth Cydia ptychora. The population increased from May to September and declined from November to April. Increasing temperatures and decreasing r.h. appeared to be associated with population decline, while the reverse seemed to favour population increase.

From light trap catches, sex ratios of adults showed considerable variation from month to month. The overall ratio was 2:1, in favour of the males, but there was a tendency for adjustment towards an apparently female-biased ratio from March to August.

Bracon (?) hancocki was found to be a major parasite. Other biotic factors contributing to population regulation included 13 hymenopterous parasites and three predators (Philodicus temerarius, Bactria sp. nr. guineensis and Chrysopa sp.)

Nutritional efficiency of four dehydrated and powdered tapioca puddings for Tribolium confusum (duVal) was assayed by studying growth, survival and fecundity of the confused flour beetle on these diets.

The common pudding inflicted about 50% mortality and caused over three-fold growth retardation in the larvae. The longevity and fecundity of the adults also were significantly reduced (P < 0.01). On the other three test puddings which contained less vitamins and more fat or carbohydrate than the common pudding, growth was even more severely retarded, and only 9% of the larvae became adults of doubtful reproductive ability. Results obtained from puddings supplemented with vitamins, or made with synthetic milk in which vitamin and fat levels were manipulated, suggest that the nutritional inadequacy of the four test puddings was mainly due to low vitamin and high fat contents.

The results demonstrate the practicality of inducing ‘self-protection’ against insect pests in certain types of food products without seriously affecting their acceptability by man.