Two mark-release-recapture experiments were carried out on a female population of A. africanus in the Zika Forest, in Uganda, to estimate density, survival rates, dispersal range and duration of the gonotrophic cycle. Marking was achieved using powdered fluorescent pigments and wet paint. In the first experiment, unfed A. africanus female mosquitoes were marked and released. A high overall recapture rate of 17.6% was recorded consisting mainly of first recaptures (up to 85.6%). The highest recapture rate was recorded during the first 4 days after release. Using Jolly's Stochastic Model, daily population estimates ranged from 1386 to 8406 during the first 7 days of release. The daily average population estimated over the first 10 days was 3591. Using the Simple Lincoln Index, population estimates ranged from 1104 mosquitoes to 16,320 with an average daily estimate of 3706. Of interest was the fact that the average daily population estimates using the two methods were not statistically significant. The 24-hr survival rate averaged over 9 days was 0.9228. Dispersal was rather random, and appeared to be of a limited range with an average distance of 50 m. In the second experiment, which involved marking only fully engorged mosquitoes, an overall recapture rate of 7.1% was recorded, with an average daily survival rate of 0.8209 averaged over the first 4 days. The pattern of recaptures indicated a gonotrophic cycle of 5–6 days with a small proportion of mosquitoes seeking secondary feeds during the first 48 hr. It was generally observed that marking and handling did not have any marked effect on mosquitoes during the first 8 days.

The susceptibility of third-instar Spodoptera exempta (Walk.) to a heat-treated nuclear polyhedrosis virus was tested in the laboratory. The polyhedral suspension was purified by differential centrifugation and heat-treated at temperatures that ranged from 20 to 90°C for 10–30 min. The LT50 ranged from 108.4 hr for virus heated at 50°C (10 min) to 162.2 hr for virus heated at 80°C (10 min). The fiducial limits to the LD50s were calculated at 0.95 probability.

Diapause in the pink bollworm, Pectinophora gossypiella, is a quantitative genetic character that is in turn regulated by external environmental factors. A naturally occurring non-diapause strain of the insect from south India and two diapause strains from Arizona (U.S.A.) were used in crosses to study the inheritance of diapause. The F progeny expressed a diapause response intermediate between the two parents and no clear dominance was evident for the non-diapause character. It was not possible to classify the phenotypes of backcross and F2 progeny in accordance with simple Mendelian ratios. Comparisons of reciprocal crosses indicated that the progeny from male parents of the Indian strain usually had a lesser incidence of diapause. Such sex related differences were more evident in F2 progeny and backcrosses. It is therefore concluded that diapause in the pink bollworm is inherited in a complex way and that non-diapause is not completely dominant over the diapause trait. The study also indicated that incomplete dominance for non-diapause involves a sex-linked gene.

A two-choice type bioassay has been used to screen extracts from a number of plants of the sagebrush community for their antifeeding properties against the Colorado potato beetle, Leptinotarsa decemlineata Say. The extracts of Artemisia tridentata, Purshia tridentata and Chrysothamnus nauseosus have been fractionated for their antifeeding constituents. Known constituents of these plants (deacetalmatricarin, coumarins, cucurbitacins, polyphenols, polyacetylenes, and essential oils) were also screened. The results indicate that several chemical classes of compounds are responsible for antifeeding activity in each plant. Water soluble substances present in the waste marc after steam distillation of peppermint oil were highly active, too.

In West and Central Africa attention has recently been drawn to the role of commercial crop plantations in the creation of new tsetse habitat, and the problems this poses to trypanosomiasis control. Reported here is the colonization by the tsetse, Glossina pallidipes Austen, of a plantation of a very different kind—exotic coniferous forest. This has been observed in two localities in Kenya: the Lambwe Valley in the west, and the Shimba Hills near the coast. The features of this habitat, and the factors associated with its exploitation by tsetse, are described, with particular reference to the Lambwe Valley situation. While extension of tsetse fly-belts by afforestation practise is unlikely to be a problem of widespread significance in Kenya, afforestation policy ought, in particular circumstances, to take into account the tsetse and trypanosomiasis situation, the Lambwe Valley being a case in point.

The spatial distribution of Cataulacus guineensis F. Smith in relation to shade regimes and also in relation to other ant species is investigated. It was found that the species prefers nesting in areas with continuous shade. It has a significant association with Oecophylla longinoda Latr. and also with Camponotus olivieri (Forel), but has non-significant association with Macromischoides aculeatus Mayr, Crematogaster depressa Latr. and Polyrhachis decemdentata Adre. The colony size of C. guineensis was also studied, and 1 to 3 nests were found to constitute any one colony. Abundance of nests and nest distribution in relation to shade regimes was examined. Observations on the insects in defending their nests are reported.

Preliminary studies on the life history and behaviour of the legume podborer, Maruca testulalis (Geyer), at Mbita Point on the shores of Lake Victoria have shown that most of the eggs (86%) of M. testulalis are laid on the leaf. Over 90% of such eggs laid on the leaf are oviposited on the lower leaf surface. Most adults were found to emerge between 2000 and 2300 hr. The number of eggs laid per female varied between 6 and 194, and over 72% of these were fertile. No larval or pupal diapause was observed.

Larval duration was 8–14 days and the pre-pupal stage lasted only 12–24 hr. The whole life cycle at Mbita Point was found to be about 20–57 days.

An important factor that previously discouraged detailed studies on the biology of M. testulalis is the fact that the eggs are translucent and extremely difficult to see against the background of the oviposition site. The discovery of these eggs was a major step in beginning to work on this important pest.

A procedure has been developed which allows production of 75,000 eggs per month of the legume pod-borer, Maruca testulalis (Geyer). More than 170 eggs per moth were obtained. The optimal number of moths placed in the mass oviposition cage having potted cowpea plants was 30. The average life-span of the moths was 7.7 and 9.5 days for females and males, respectively. The optimal number of larvae in the rearing box was 50: larval survival declined sharply above a density of 50 per box.

Proteins of male accessory reproductive gland secretions and the spermatophore of the tsetse, Glossina morsitans morsitans, have been characterised by electrophoresis. The spermatophore contains all the major proteins of accessory gland secretions and no new proteins were detected.

Influence of blood meals and neurosecretions on synthesis of accessory gland secretions and insemination are discussed. It is concluded that synthesis of accessory gland secretions commences prior to adult emergence and continues uninterrupted in the adult, independent of the corpus allatum.

The phytosterols inokosterone, makisterone A, ecdysterone and ecdysone were effective growth regulators and abortifacients (70%) at estimated doses of 1.4 × 10−4 M, 6.8 × 10−4 M, 5.2 × 10−5 M, and 7.8 × 10−5 M respectively when fed to female tsetse Glossina morsitans morsitans. The sterols, added to defibrinated cow or pig blood, were fed to the flies in an in vitro system through a silicone rubber membrane. Cyasterone and ponasterone A were only slightly effective, therefore the hydroxyl groups on the side chain appear to confer activity. Evidence is presented to support three hypotheses which may be advanced to describe the mode of action of the sterols, namely:

(a) Synthesis and/or release of the ‘milk’ secretion from the uterine gland is significantly retarded.

(b) Although the size of the blood-meal is normal, digestion of the in vitro meal is very slow.

(c) Development of the larva itself may be affected by the presence of the hormonally active sterol (or a metabolite) in the ‘milk’.

Effective dose of sterol causing 70% abortion in flies is very much lower than that dose required when injected into the haemolymph. The Malpighian tubules very rapidly excrete the sterol. Therefore, either (1) a slow release of sterol or metabolite into the haemolymph is necessary to disrupt ‘milk’ production, or (2) digestion of the treated in vitro meal itself (and subsequent meals as well) is so retarded that the larva in utero is effectively starved.

Studies on the resting site preferences of the tsetse, Glossina palpalis gambiensis Vanderplank, were conducted in a gallery forest in the Northern Guinea Savanna in Mali. Tanglefoot was used to trap flies alighting to rest on the various site-types investigated. Five site-types were observed: boles, fallen logs, undergrowth (‘bush’), branches and tree canopies. Observations were made in the warm rainy, warm dry and hot dry seasons.

Distribution of resting flies on site-types was significantly heterogenous in each of the seasons. More than 80% of flies collected in each of the three seasons were found on fallen logs. Generally, there was no significant difference in numbers found on the top or side of fallen logs. Boles were the next best preferred site-type. Approximately 90% of flies on boles were collected below 1.0 m and none was found above 2.0 m. Few flies were collected from the undergrowth (bushes), tree canopies and branches. Similarities and differences between results obtained from the present study with those of other workers are discussed. The importance of the results in ground insecticide control operation against this species is noted.

Pirimiphos methyl when sprayed at dosages of 10 and 15 p.p.m., effectively protects dehusked maize in cribs for 3 months against incipient or cross infestation by stored product insects. Longer storage would however require a reapplication of the insecticide. At 5 p.p.m., pirimiphos methyl is not a protectant against insect infestation of maize stored beyond 1 month.

As insect numbers and grain damage increased, viability of infested maize decreased. Only when grain embryo is damaged or endosperm destroyed can insect infestation prevent grain germination.

The effect of six pyrethroids, NRDC 104 (resmethrin), NRDC 107 (bioresmethrin), NRDC 119 (cismethrin), NRDC 143 (permethrin), NRDC 156 and allethrin, against larvae and adults of the Egyptian mosquito Culex pipiens L. has been evaluated. Five strains were used, a field strain and DDT-susceptible, DDT-resistant, malathion-susceptible and malathion-resistant strains. Results obtained were also referred to a DDT highly susceptible strain of another mosquito Aedes aegypti (L.)

The toxicity curves showed that NRDC 156 proved to be the most effective compound tested, followed by NRDC 143, NRDC 119, NRDC 107 and NRDC 104, respectively, while allethrin was the least effective. Such a fact was highly pronounced either on the LC50 or on the LC95 basis.

As larvicides, data obtained proved that the DDT-susceptible strain was less susceptible to all the tested pyrethroids than the DDT-resistant strain by about 42.6-, 5.1-, 8.6-, 132-, 290.7- and 4.8-fold in the case of NRDC 104, 107, 199, 143, and 156 and allethrin, respectively. Tests also showed that there is no definite variation in susceptibility of both malathion-susceptible and malathion-resistant strains, except in the case of NRDC 143 and 156. Comparing tests against larvae of A. aegypti confirmed that the susceptibility to these pyrethroids was closely correlated with insect species and its strain, and cross-resistance might be developed among larvae of these species.

As adulticides, the pyrethroids used could be arranged in the following descending order according to their LC50 values: NRDC 156, NRDC 143, NRDC 104, allethrin, NRDC 107 and NRDC 119. The change in the trend of toxicity is possible due to the stage tested and the mode of action of these compounds on adult or larval stage.