To find out if it were possible to reduce wireworm populations by means of seed dressings which are convenient to use, and desirable in other ways, the direct and residual effects of insecticides on wireworms (Agriotes spp.) attacking spring-sown and winter-sown wheat were tested on a clay soil at Rothamsted, Hertfordshire. Treatments comprised dressing seed with dusts containing 20% (standard) and 60% (high-rate) γ-BHC and 40% (standard) dieldrin, all at 2 oz. per bushel, 60% dieldrin at 70 oz. per bushel (high-rate), or a liquid containing 30% dieldrin at 1 fl. oz. per bushel; combine-drilling 0.5% γ-BHC dust at 1 cwt. per acre with the seed; and spraying the soil surface after sowing with 1 gal. 30% aldrin in 40 gal. water per acre. The high-rate BHC and dieldrin seed dressings, the combine-drilled BHC dust and the aldrin spray significantly reduced wireworm populations when applied to spring- or winter-sown wheat, the reduction in the former case being apparent two years later in one experiment; these reductions were, in general, reflected in increased yields. The standard seed dressings tended to be less effective. Similar results were obtained in an experiment on a fen peat soil in Lincolnshire.

Tests done in one experiment on plots sown with dieldrin-dressed seed showed no evidence that birds grub up plants or seeds that would otherwise have germinated.

Data were obtained on survival and development of larvae of Distantiella theobroma (Dist.) on cocoa seedlings maintained under three water régimes, high (HW), intermediate (IW) and low (LW). Recorda were taken of plant growth and damage by feeding. The water régimes of some plants were reversed in the latter part to the experiment.

Larvae soon completed development on HW plants, but on LW plants a large number died, possibly because they were unable to take up fluid fast enough to offset loss by evaporation. There was intermediate mortality on IW plants.

Larvae took longer to develop on IW than on HW plants, probably because they imbibed nutrients at a reduced rate.

More larvae survived on LW plants that were regenerating after increase in water status than on plants that had received abundant water continuously. They fed mainly on the old wood and very little on the soft regenerative shoots, so were apparently favoured by some change in the peripheral tissues of the main stem.

On HW plants, nearly all feeding took place on woody or partially hardened tissue; newly flushing tissue was not fed on if it was growing normally. On IW plants, the expansion of new terminal leaves was often slow, and these tissues were then attacked by young larvae. This happened much more on LW plants, where the apical region was killed by persistent feeding. On all plants larvae older than second instar fed only on hard tissues.

Later effects of feeding were splitting of the wood where lesions had been made and sometimes the development of fungal infecdtions. The most severe infections occurred when the upper part of the old stem died back on LW plants that were regenerating after increase in water status.

Between June 1964 and May 1965, samples of Glossina pallidipes Aust., G. palpalis fuscipes Newst. and G. brevipalpis Newst. were caught in an area on the north-eastern shore of Lake Victoria in Uganda. Both males and females were classified into age-categories according to the degree of wear of the wings. Females were also classified into ovarian age-categories according to the exact or approximate number of ovulations that had taken place. All were examined for presence of infections with Trypanosoma, which were classified as vivax-type, congolense-type or brucei-type according to their location in the flies.

The percentage compositions of the samples by wing-fray category are compared. The mean wing-fray category of females of G. palpalis fuscipes and G. brevipalpis was somewhat lower, and that of females of G. pallidipes somewhat higher, than that of the corresponding males. However, the figures for infection rate in females of all three species were higher than in the corresponding males, significantly so in G. pallidipes and G. palpalis fuscipes, and it seems probable that the mean age of females, at least of the two latter species, was greater than that of males. Among females, the range of calendar ages of flies in the various fray categories was wide.

The physiological age-determination method, in which females older than about 42 days are classified iDto four age-categories, does not extend sufficiently far to give a reasonable pattern for the age-composition of any of the species at Lugala, and many of the individuals caught must have been more than about 80 days old.

Seasonal fluctuations in mean wing-fray and in the proportion of old flies in the population were correlated with changes in infection rate of females of G. palpalis fuscipes but not of females of G. pallidipes. Among males of neither species were seasonal fluctuations in mean fray correlated with changes in infection rate, though among those of G. palpalis fuscipes the two varied similarly between June and February.

Females of G. pallidipes and G. palpalis fuscipes about 31–42 days old had significantly fewer brucei-type infections than those over 42 days old, and either the developmental cycle in the field must normally be longer than that recorded in laboratory investigations or many of the flies must become infected when more than just a few days old.

The nutritional state of males of Glossina morsitans Westw. (subsp. orientalis Vanderplank) obtained by two different methods from four vegetation types at two contrasted seasons during 1964–65 in Rhodesia was assessed by determining their fat content, haematin content and size. The results showed that even in the hot dry season, when Brachystgia and Commiphora woodlands were leafless, the nutritional state was better in flies from these two vegetation types than in those from evergreen riverine fringe vegetation; in the rainy season, the difference persisted but was smaller. Only in Combretum bushland, which is sparsely wooded, did the poor nutritional state of flies caught in both seasons accord with the relatively inhospitable appearance of this vegetation type.

The total food-reserves (fat plus the fat-equivalent of haematin) were higher in flies captured on fly-rounds than in those captured on bait-oxen, but the difference was smaller in populations under nutritional stress, e. g., in flies from riverine fringe vegetation and Combretum bushland in the hot season, which suggests that the period of sexual appetitive behaviour in males is shortened under conditions of nutritional stress.

The implications of these results are discussed in relation to methods of control that involve discriminating between parts of the tsetse habitat.

The identity of the palm kernel borer in West Africa is established, its correct name being Pachymerus cardo (Fåhr.); a neotype is designated for P. bactris (L.), the type species of Pachymerus Thunberg; a new species, P. thoracicus, is described from Paraguay, and three new specific synonymies are made. A key in given to the species of Pachymerus, the definitive characters of all of which are described and illustrated.