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.

The variations of moisture in the leaf litter of Eucalyptus tally with the fluctuations in the populations of microarthropods of the litter. The acarines and collembolans are the most numerous. We note at the end of the rains a spectacular rise in the rate of increase of psocids in this litter, as well as an obvious drop in the population of entomobryomorph collembolans (specific prey of Smithistruma) which have begun to penetrate the soil looking for moisture. An analysis of the sampling of prey carried back to the nest by foraging workers shows that, whatever the season, the capture of entomobryomorphs is the highest. In the rainy season, the majority of the prey are these entomobryomorphs; while, with the coming of the dry season, the rate falls to 31 then 21%. On the other hand, the foraging workers catch psocids, Acarina, and termite larvae by way of compensation.

Research on stem borer pests of sugarcane, maize and rice in Ghana is briefly reviewed. The work on the biology of the borers carried out at Asutsuare between October 1977 and January 1980 has pinpointed the fact that the practice of ratooning is the principal cause of a devastating build up of stem borers in the sugarcane fields. Cost/benefit analysis has revealed that as a result of discontinuation of this practice, there would be an initial gain of $13.4/ha. The profit should increase in subsequent years when the foci of borer infestations are removed as a result of the discontinuation of ratooning. The use of imported parasites as well as insecticide treatment in controlling the borer populations has been ineffective. Further work in developing novel control measures against sugarcane borers is still in progress. Only cultural methods have been found useful in limiting the damage caused by stem borers to maize. Losses caused by stem borers to the rice crop in Ghana are still not well established.

This paper reviews work on techniques in mass rearing of insect pests, especially stem- and pod-borers. The account covers advances in rearing of insects on native host plants and on artificial diets and possible ways of use of these insects in host plant resistance research.

The population of green spider mite Mononychellus tanajoa (Bondar) was monitored on cassava for 52 weeks (mid October 1979 to mid October 1980) at Moor Plantation, Ibadan, Nigeria. Mite population was found to be high in the dry season (80.1 ± 57.7 per leaf) and low in the wet season (15.2 ± 13.5). There was a linear relationship between mite population and the weather factors investigated. The relationship was positive in the cases of temperature and radiation, and negative in those of rainfall and humidity. The high mite population in the dry season was attributed to the high temperature (27.9 ± 1.26°C) and radiation (39.1 ± 7.86) conditions which favoured development of the different stages in the life cycle of the mite. The low population in the wet season was attributed to the adverse effects of high rainfall (56.31 ± 33.14 mm) and humidity (87.29 ± 2.36%) on the mites. Seasonal fluctuations in mite population was attributed to the physiological condition of the host plant.

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.

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 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.

Changes in the activities of general esterase, L-alanine:2-oxoglutarate aminotransferase (GPT), L-aspartate:2-oxoglutarate aminotransferase (GOT), acid and alkaline phosphatase after allatectomy, brain-cauterization and juvenoid treatment have been studied. It has been shown that allatectomy reduces the GPT, GOT, general esterase and acid phosphatase activity in all tissues from both sexes and alkaline phosphatase activity in all the cases excepting the testis. Treatment with juvenoid in allatectomized insects reverses the effects of allatectomy. Both allatectomy and brain-cauterization cause the drastic decrease of all the enzymes in both sexes. The physiological significance of these findings has been discussed in this paper.

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.

Topical application of the juvenile hormone mimic 1™75 to pregnant Glossina morsitans 15 or 20 days after emergence resulted in a significant increase in abortions of eggs and larvae of all developmental stages. Small doses (0.25 ng per fly) were sufficient to elicit a response which was more pronounced if application occurred 20 days after emergence. Flies fed once on rabbit ears, which had been treated with 5 ng of the mimic per ear, resulted in abortions and the effect persisted for up to 40 days. The hormone mimic did not induce abortions in isolated pregnant uteri kept in organ cultures for up to 7 days.

Four species and subspecies of rats and mice (Rattus norvegicus, Arvicanthis niloticus niloticus, Mus musculus and R. r. frugivorus) were found associated with a new irrigated area, El-Galaa, about 55 km from the edge of the desert near Alexandria, Egypt. Ectoparasites recovered from these hosts were three species of fleas (the Oriental rat flea Xenopsylla cheopis Rothschild, the human flea Pulex irritans Linnaeus, and the cat flea Ctenocephalides felis felis Bouche). three species of sucking lice (Polyplax spinulosa Burmeister, Polyplax abyssinica Ferris, and Hoplopleura capitosa Johnson), and five species of mites (Ornithonyssus bacoti Hirst, Laelaps keegani, Dermanyssus spp., Haemolaelaps spp., and Echinolaelaps echidninus Berlese). Records showed that the lice were the most abundant ectoparasites (39.03%) recovered from their rodent hosts, followed by the mite species (36.82%) and finally the fleas (24.1%). Lice in general and fleas (especially X. cheopis) showed a certain degree of host specificity as compared to other ectoparasites. A close correlation has been shown to exist between the incidence of flea and lice species (but not the mite species) and the incidence of some rodents.

Resting site preferences of the tsetse Glossina morsitans submorsitans Newstead were studied in a savanna woodland and gallery forest in the Northern Guinea Savanna of Mali. Five site-types [boles, fallen logs, undergrowth (‘bushes’), branches and tree canopies] were observed. Flies alighting to rest on these site-types were trapped on tanglefoot. Observations were made in the warm rainy, warm dry and hot dry seasons.

Boles were dominant as the preferred resting sites in the savanna woodland in all seasons; fallen logs were the next preferred site-type, while few flies were collected from the undergrowth, branches and tree canopies. Approximately 90% of flies on boles were collected below 1.0 m and none were found above 2.5 m.

During the hot dry season in the gallery forest, the undergrowth was the most preferred site-type; unshaded undergrowth accounted for approximately 98% of all flies on the undergrowth. Fallen logs and boles were the next preferred site-types; branches and tree canopies recorded very few flies. Probable reasons for the results obtained and the importance of these results in tsetse control operations are discussed.

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.

Surveys on the stem borer complex of rice were initiated at Mbita Point Field Station during 1980–1981. Stem borers collected and identified so far included Maliarpha separatella Rag; Diopsis thoracica West; Sesamia calamistis Hmps., and Chilo partellus Wlk. Among these four species, M. separatella was the most abundant and showed highest infestation during the reproductive and ripening phases of the rice crop. D. thoracica was found to cause greatest damage on the crop during the crop's tillering phase. It is suggested that there may be differences in Maliarpha infestation due to rice varieties.

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.

Maliarpha separatella (Rag) was found to infest the rice crop for the greater part of the crop's growth cycle. There was an extended peak of larval activity, and the build up of the larval population was correlated with stand establishment and stem development. The intensity of both tiller infestation and internode tunnelling was found to increase with the crop maturity. Some aspects of control measures of the pest as related to the insect-pest/host-plant relationship are discussed.

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 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.

Between 1979 and 1980, the incidence, breeding sites and infection rates of Simulium damnosum with Onchocerca volvulus were investigated on rivers Amire-u-Kiriki and Katsina Ala in a local government area of the Benue State of Nigeria, in West Africa. Several breeding sites were located along the rivers. All the Simulium caught were identified as S. damnosum, and a greater number was encountered during the rainy than the dry season. The numbers of infected and infective S. damnosum were ascertained through the dissection of the caught flies; the number of bites per day as well as the number of infective bites per person per day were estimated for each zone of investigation. It was concluded that the areas of investigation are highly endemic for human onchocerciasis, and the consequences of this on the people living in the area are discussed.