The results of sixty 24-hour catches of mosquitos carried out with man as bait in the forest canopy at Zika, central Uganda, are discussed. In these catches the arrival of mosquitos was recorded to the nearest minute.

The rapid changes of light intensity in the equatorial twilight are discussed in relation to a series of readings made at Entebbe.

It is shown that among species that show a crepuscular peak of biting activity (Aedes ingrami Edw., A. africanus (Theo.), Mansonia fuscopennata (Theo.) and M. aurites (Theo.)) the peaks do not all occur at the same time, but form a succession.

Moonlight (at least in the forest canopy) has no apparent effect on the timing of these crepuscular surges of biting activity.

One species (M. fuscopennata) also shows a peak of biting activity before sunrise. This peak is closer to sunrise than the evening peak is to sunset. A brief reference to current work carried out above the canopy, where foliage, shadows, etc., do not complicate the environment, shows that this phenomenon occurs in other species also. It is concluded that in these species the morning peak must almost certainly occur in light of much greater intensity than the evening peak.

The implications of these findings are discussed with reference to the questions of endogenous rhythm and exogenous stimuli.

One of the principal pests of cowpea (Vigna unguiculata) in southern Nigeria is Laspeyresia ptychora Meyr., the larvae of which attack the seeds within mature pods and cause considerable loss of yield. It has not so far been recorded from northern Nigeria. Details of the life-history of this Eucosmid are described from laboratory and field observations made in Nigeria in 1962–63. Eggs are laid on mature pods, which the larvae enter very soon after hatching, feeding on the seeds within. Pupation normally takes place in a cocoon in the soil, but pupal development can be completed in the absence of soil and of a cocoon. Four generations normally occur on the two crops of cowpea that can be grown each year in southern Nigeria, a complete first and a partial or complete second generation on each; but five generations may sometimes occur. The pest survives through the dry season and between the two crops in the rainy season by means of generations that develop on stand-over and volunteer cowpea, on leguminous plants grown in market gardens, and possibly on some yet undiscovered wild plant. No diapause in any stage was observed.

Annual fluctuations in larval populations and levels of infestation are described in relation to the cowpea crops and to the damage caused. In a field trial in 1963, 35 per cent, (by weight) of seed from the early crop and 20 per cent, of that from the late crop was damaged. These figures take no account of seed that was completely destroyed, so that the true losses are greater than they indicate. Damaged seed is usually unmarketable as a result of contamination with frass and webbing.

Investigations showed that, although larvae may be carried into stores when the crop is harvested, L. ptychora cannot become a pest of stored cowpea seeds because it is unable to develop on dried seeds.

The possibilities of chemical, cultural and biological control are discussed, the latter not at present being promising. Field trials with γ BHC, dieldrin, carbaryl, isobenzan and phosphamidon were carried out; only the last-named, which is a systemic insecticide, showed promise of affording satisfactory control. The difficulties of successfully attacking L. ptychora with insecticides are discussed, and it is concluded that chemical measures will need the support of modified cultural practices, particularly those directed towards destruction of stand-over and volunteer cowpea plants, if a satisfactory level of control is to be achieved.

Details of the insect and mite infestation encountered on food commodities imported into Britain from the United States of America between 1953 and 1961 are given. Twenty-eight species of insects and nine species of mites, thought to have been introduced with the goods are listed together with a further 35 species of insects thought to have been derived from ships' holds. Emphasis is laid on the dangers of foodstuffs acquiring infestation either by cross-infestation or from infested residues in the holds.

The life-cycle of five stocks of Cadra cautella (Wlk.) (Phycitidae) and the duration of the various developmental stages were studied at temperatures from 15 to 37·5°C. and relative humidities between 0 and 100 per cent, on a mixture of wheatfeed, wheat germ and yeast. At 70 per cent. R.H., the limiting temperatures for the completion of the life-cycle were about 15°C. and about 36°C. At 30°C., the limiting humidities were about 20 and above 90 per cent. R.H. Development was quickest at 30–32°C. and 70–80 per cent. R.H., taking 29–30 days from the laying of the egg to the formation of the adult moth. This period increased with lower temperature and humidity, reaching 145·0 days at 15·5°C. (70 per cent. R.H.) and 51 days at 20 per cent. R.H. (30°C.).

Near the optimal conditions for rapid development, the egg occupied about 10 per cent, of the developmental cycle, the larva about 70 per cent, and the pupa 20.

Temperature influenced the duration of all developmental stages, but humidity had a marked effect only on the larva. The pupation of some mature larvae was delayed: whether or not this delay is a diapause is discussed. Virgin adults lived 4·8 days at 35°C. to 18·9 days at 17·5°C. (70 per cent. R.H.). At 30°C., low humidity halved the length of adult life.

The mortality, even in favourable conditions, was often rather high, principally among eggs and young larvae.

There was poor survival of small numbers of larvae kept on maize and on cocoa beans, but survival on wheat was similar to that on the usual food mixture. The developmental period on wheatfeed alone was shortened by the addition of honey or glycerine or a combination of wheat germ and yeast.

The incidence of disease is discussed.