Occurrences of outbreaks of the African armyworm, Spodoptera exempta, between January and December for 19 years (1961–1979), and records on nightly moth catches from light trap stations located between southern Kenya and east-central Tanzania (1–8°S and 35–41°E) for 16 years (1963–1978), have been mapped, tabulated, and analysed on a standard weekly time-table, in order to compare events occurring between the ‘off-season’ months of July to November and the beginning of the ‘outbreak seasons’ from December or January. Circumstantial evidence from the above, coupled with analysis of climatological statistics for rainfall, temperature and windflow over the area and period, support the hypothesis that populations of S. exempta can survive between southern Kenya and eastcentral Tanzania during the off-season months, and contribute to the initial development of ‘outbreak seasons’ in Tanzania or Kenya. Methods for monitoring and analysing such developments for improving the efficiency of the Armyworm Forecasting Service in East Africa are suggested.

This paper is an attempt to synthesize information available on C. p. quinquefasciatus in Africa. The latter is presently found in most urban areas of the African continent and in rural settlements which show some trends towards urbanization. In East Africa, and the islands of the Indian Ocean, C. p. quinquefasciatus is one of the major natural vectors of Wuchereria bancrofti. In addition it can also transmit, under laboratory conditions, some other pathogenic agents.

Preimaginal forms develop in different kinds of man-made breeding-places, especially those containing polluted water. The situation in each African region is reviewed in detail.

Female behaviour during the different phases of the gonotrophic cycle is analysed, together with population dynamics.

Control methods by synthetic insecticides are discussed in relation to resistance problems and the characteristics of the breeding sites. Other control methods based on the use of growth regulators, genetic manipulation, biological agents (parasites and predators) and environmental management have been investigated as well. Most of them cannot be easily applied or are not yet applicable for control operations.

The head capsule widths of larvae of the cowpea pod-borer Maruca testulalis, reared individually and crowded together in the laboratory were measured. The measurements were subjected to a test of analysis of variance, frequency distribution and Dyar's rule. All methods gave a total of five larval instars in the life cycle and conformed to Dyar's rule. There was a high positive correlation (r = 0.97) between the size of the head capsule and the period of development elapsing. The minimum duration of larval development was 9 days.

Changes in the physiological status of the host rice plant had a profound effect on wing morphism in the brown planthopper, Nilaparvata lugens (Stål). Significant increases in macroptery in the hopper progenies reared on senescent or hopperburned hosts occurred mainly because of a general decline in the host's nutritional status and allelochemic factors. Starvation of young nymphs on nutritionally-depleted hosts probably inhibits the secretion of juvenile hormone by the corpus allatum, suppressing brachyptery and expressing macroptery. Also, any juvenilizing effect of the host's allelochemics would tend to dissipate with the host's senescence. Therefore, the proportion of macroptery in the hopper progeny developing on the rice host plant is determined by the extent of depletion of the host's nutritional allelochemic factors. The observed significant increase in macroptery at a density of 50 or more hoppers per plant may have also been mediated through the host plant. Brown planthopper progenies of macropterous and brachypterous Biotypes 1, 2, 3 and the field population differed in their expression of macroptery probably because of their inherent differences in sensitivity to macropteryinducing stresses.

Non-setting adhesives available were assessed for catching insects of medical and veterinary importance. Physical, chemical and handling properties are described. The results of tests are given using the most suitable adhesives against Glossina spp. (tsetse), Aedes aegypti (mosquito), Lutzomyia longipalpis (sandfly), triatomid bugs and cockroaches. Details are given of a formulation suitable for the capture of most insects in a variety of climatic conditions. The manufacturer's addresses are given to prevent difficulties in ordering and obtaining these products.

The existence of phase variation in S. exempta has long been known and the possible significance of the phenomenon in terms of the insect's life-system has been discussed previously (Rose, 1979). Present studies carried out on a comparative basis have shown meaningful differences in many attributes of solitary- and gregarious-phase caterpillars.

The solitary-phase caterpillars take longer to develop, possess more protein fractions and higher levels of juvenile hormone in the haemolymph of sixth instars, and their pupae consume more oxygen compared to the gregarious ones. It is suggested that the solitary form of larvae is the normal type for the species, while the gregarious form is able to make maximum use of resources during some parts of the year.

The dwarf variety of coconut, Cocos nucifera L. (Palmae), was found to be eaten by the larvae of the African armyworm, Spodoptera exempta (Wlk.). The comparison of the armyworm infestation on the leaves of the coconut seedlings and the adjacent grass species revealed lower larval density and growth rate on coconut seedlings. This observation suggests that a small population of the African armyworm can survive and develop on the leaves of the dwarf variety of coconut.

Population studies of the whitefly, Bemisia tabaci, carried out in the field indicated that whiteflies were present in cassava all year round and that there were marked seasonal fluctuations in the population levels. Possible explanations for these fluctuations are discussed. It was found that the interaction of atmospheric temperature and relative humidity was highly correlated (r = 0.924) with the development of the whitefly. Results of the studies suggested that rainfall has an indirect effect on whitefly population. Whether B. tabaci behaves in the same way in mixed cropping system has not yet been established.

The development and morphology of the immature stages were examined by means of dissections, linear measurements, light and scanning electron microscopy of the egg, the larval instars and the puparium.

The measurements were of body lengths and widths and the lengths of the cephalopharyngeal skeleton. Observations on the morphology of the immature stages concentrated on the surface structure of the egg, the head capsule, the anterior and posterior spiracles, the ventral plate and the cephalopharyngeal skeleton of the different larval instars.

Development and survival of larvae at different growth stages of the sorghum plant were investigated in the laboratory. Survival and rate of larval development were dependent on the size of the host plant. Survival was usually highest when plants about 2 weeks old were infected, low in very young plants and lowest in plants more than 50 days old. Within groups of insects hatched from eggs laid on the same day, the occurrence of various larval instars overlapped. The first instar was found from the 2nd to the 8th day after egg-laying, the second instar from the 4th to the 12th day, and the third instar from the 5th to the 18th day. Pupation started on the 14th day and adults started to emerge on the 21st day.

The goatweed, Ageratum conyzoïdes L., contains the same chromenes, precocenes 1 and 2, as the bedding plant, A. houstonianum. A crude lipid extract from the goatweed exerts ovicidal action and induces sterility after topical treatment of both young last instar larvae (L6) and females of Dysdercus flavidus Sign, at emergence by inhibiting ovarian development. The chromenes survived metabolism for at least 12 days. The action of the two chromenes in the crude extract is synergistic.

The relative efficacy of 25 acaricides, applied topically to the engorged adults of B. microplus was in the following order: chlorfenvinphos > tetrachlorvinphos > dimethoate > chlorpyrifos > fenitrothion > dicrotophos (LC50 = 0.000897−0.00244%) > naled > propoxur > crotoxyphos > pirimiphos ethyl > coumaphos > dioxathion (LC50 = 0.00425−0.00534%) > trichlorphon > lindane > carbaryl > allyxycarb > diazinon (LC50 = 0.00737−0.0149%) > promecarb > ethion > chlorpyriphos methyl > chlormebuform (LC50 = 0.021−0.0593%) > clenpyrin > chlordimeform > pirimiphos methyl > phosphamidon (LC50 = 0.1566™0.275%).

The order of toxicity is different from their relative efficacy against the larvae of the same population of the tick. Applied implications of the results are discussed.

Coprophagous beetles belonging to two genera, Onitis and Heliocopris, were collected and fed on proglotids and eggs of Taenia saginata. The beetles' faeces was collected after 24 hr onwards and examined for Taenia eggs. The flight range and behaviour of the beetles was investigated using cow rumen contents as bait for starved marked beetles. Results indicate that coprophagous beetles could play a role in dissemination of taeniasis.

Polyacrylamide gel disc electrophoresis of the salivary secretion from the tsetse, Glossina morsitans morsitans Westwood, showed 11 protein bands, four of which were characterized as glycoproteins. Sixteen amino acids and four sugars in the hydrolysates of saliva were identified. Thin layer chromatography showed five lipid classes and three phospholipids. The secretion is a clear, transparent, viscous fluid with a pH between 7.00 and 7.5. These findings are discussed in relation to the nutritional requirements of the metacyclic forms of trypanosomes that may be found in the salivary glands.

Contact application of precocene 2 (6,7-dimethoxy-2,2-dimethylchromene) to inseminated adult female bed bugs inhibited egg maturation and affected egg viability. Third-stage nymphs exposed to 100μg/cm2 showed precocious maturation after the moult to the next stage. Nymphs exposed to lower concentrations of precocene exhibited teratism of the antennae, including the reduction of terminal sensillae. This was thought to be responsible for the bugs not assembling.

Reduction in the fecundity in adult bugs, and the morphogenetic and teratogenic activity in nymphs was circumstantially related to reduced levels of juvenile hormone, as a result of exposure to precocene.

Effects of age and hunger on the pattern of sound production in the tsetse, Glossina morsitans morsitans Westwood were determined. Although an afternoon peak was evident in young flies only on day 1 and virtually absent on all days in mature flies of both sexes, sound production in 12:12 LD basically seemed to follow a ‘U’-shaped pattern typical of other diel responses. Experiments under constant light (LL) and constant dark (DD) conditions did not indicate a clear circadian rhythm associated with sound production. Food deprivation led to a decrease in total daily sound production in contrast to other activities in G. morsitans morsitans.

Laboratory and field studies were made to investigate the toxicity, mode of action, and persistence of technical DDT and y BHC when applied to the cashew in Sri Lanka to control the mirid bug, Helopehis antonii Sign. The insecticides were tested at concentrations previously used in field trials.

Mirid nymphs were placed on the nuts and the rate of knockdown and mortality after exposure for a test period was recorded. These tests showed that BHC had a higher toxicity and acted more quickly than DDT. BHC had a powerful and transient fumigant action over DDT, which had no fumigant effect at all. Persistence was studied by treating cashew leaves and nuts growing under natural conditions and then testing the residual deposit at intervals.

It was concluded that BHC would be more effective than DDT when treating mature cashews because, in addition to its higher toxicity and quicker action, its fumigant action would compensate for incomplete coverage by low-volume spraying.

Larvae of the Caribbean fruit fly, Anastrepha suspensa Loew (Diptera: Tephritidae) parasitized by the wasp, Biosteres longicaudatus Ashmead (Hymenoptera: Braconidae), were topically treated with diflubenzuron (Dimilin®), a chitin synthesis inhibitor, at 100, 500 and 1000 ppm. Each dosage was initiated during the parasite's egg stage, each of four larval stages and the pupal stage (pharate pupa + pharate adult). Adults emerging from all immature stages treated with the two higher dosages were significantly (P < 0.05) fewer than the controls. Developmental stages, in decreasing order of susceptibility to diflubenzuron were: egg, first instar, pharate adult, pharate pupa and larval stages two to four. Abnormally developed ovipositors occurred in some adults which emerged from eggs, pharate pupa and pharate adults that were treated with the two higher concentrations. Such females were unable to successfully locate and parasitize hosts. Females with normal ovipositors which emerged from treated eggs and pharate adults were able to find and attack hosts but had significantly fewer eggs in their ovaries and oviposited less than the controls. The F1 eggs laid by these females developed normally and survived to adulthood with no apparent abnormalities.

—The flesh fly, Sarcophaga ruficornis Fabr., was fed on thiotepa, and it was found that a 1% thiotepa solution produced complete sterility, which was due to the damage to the follicle cells and nurse cells. The passage of the female protein, ‘vitellogenin’, was blocked. Therefore, no trace of yolk granules was visible in the treated oocytes, but the oocytes and cytoplasm of the nurse cell contained vacuoles, and their nuclei were characterized by clumped chromatin contents.

A study was carried out during the wet and dry seasons, between October 1978 and May 1980 (altogether comprising four wet and three dry seasons), on the trypanosome infection rate in the tsetse species, Glossina pallidipes Austen, in rural situations in the Kiboko and Nkruman areas in Kenya. There were some sex and age differences with respect to trypanosome infection. Female tsetse showed higher infection rates, and old flies, both male and female, also showed relatively higher trypanosome infection rates. Infections with Trypanosoma vivax and T. congolense were different, both as regards to seasons and locality: the infection rate with the latter was higher in Kiboko than in Nkruman, and varied seasonally; while the infection rate with T. vivax did not vary significantly with seasons. The kind of traps used for sampling tsetse influenced the trypanosome infection rate indirectly by having a direct influence on the age structure of tsetse. The vertebrate hosts of tsetse in the two areas played an important role: the infection rates of tsetse with T. vivax and T. congolense were high in areas with a high density of bovids.