1. The Viburnum aphis, Aphis (Doralis) viburni, Scop., is described and compared with two other species, A. fabae, Scop., and Ceruraphis eriophori, Wlk., also found on Viburnum opulus.

2. Transference experiments show that colonies can be established artificially on Euonymus europaeus and Rumex obtusifolius, but not on other common host plants of A. fabae.

3. The sexupara is apterous and produces mixed colonies, thus differing from A. fabae where an alate gynopara produces only oviparae, the males arising from an apterous mother on the summer host.

In Melophagus ovinus, derris dust is shown to be absorbed through the spiracles and tracheal system. The amount of dust entering the tracheae is governed by the structure of the inspiratory spiracles and the rate of flow of the inspired air.

Factors stimulating the rate of respiration of the insect—i.e., increased muscular activity, the presence of 5 per cent. carbon dioxide and a rise in temperature, increase the rate of entry of derris into the body.

Penetration of derris takes place slowly through the external cuticle at 30° C., but not at all at 20°C. It is postulated that the entry of derris through the cuticle probably depends on the hardness of the lipoid layer.

This paper describes part of an extensive programme of research on new methods of controlling body lice carried out during 1940–1942. The work was initiated by Professor P. A. Buxton, F.R.S., with whom the writer was privileged to collaborate, and financed by grants by the Medical Research Council. The results proved for the first time the possibility of continuous protection against body lice over a period of several weeks after treatment. To some extent, the materials and methods of achieving this have now been improved or superseded; but it has seemed worth putting on record some details of technique and the results for their scientific interest.

1. The work was carried out in Bwamba County, Uganda, a district where human yellow fever has recently occurred. It consisted mainly of 24-hour catches in banana plantations and rain forest combined with climate observations.

2. It was found that forest was cooler and moister by day than a banana plantation while the plantation was cooler and moister than the open air. By night, however, the climate of all three environments was strikingly similar.

3. Methods used in making 24-hour catches and large scale routine catches are described. Trials with trap nets showed these to be less efficient than hand catching.

4. Experimental catches showed that Aëdes simpsoni, the only species known to be a vector of yellow fever in Bwamba, bites mainly in coffee gardens, maize fields and the thinner parts and edges of banana plantations. It is scarce in fully exposed situations. It occurs within the edges of primeval rain forest. It prefers human blood to that of goats, fowls, and monkeys, and attacks the head and shoulders selectively.

In 1925, the writer (2) described some experiments that demonstrated the rôle of Helopeltis as a pest of cotton at Ibadan, Nigeria. Evidence was obtained that attack was greater on the improved indigenous Ishan (Gossypium barbadense, formerly described as G. vitifolium) than on either American Allen (G. hirsutum) or the ordinary native cotton (G. peruvianum).

A cage colony of Anopheles pharoensis, Theo., was established in September, 1943. The methods used were mainly those described by Hackett in his paper on the Malaria Station in Tirana, read at the Amsterdam Malaria Congress in 1938.

In the subgenus Mochthogenes, only the pupa of Culex (M.) inconspicuosus, Theo., has been described. Since one of us (M.P) has obtained the immature stages of all the known species, including C.(M.) castor, De M., we take advantage of this opportunity to give a key to the pupae. The pelts were all obtained from specimens bred in isolation at Yangambi, Belgian Congo, and the resulting adults identified by means of the male terminalia.

(1) The methods of breeding larvae of Capnodis are described.

(2) A description of the larva and of its methods of locomotion is given.

(3) A study of the reaction of the larva to external stimuli is presented. It is pointed out that phototropic or geotropic reactions have no influence on the activity of the larva and that it is guided to its food through stereotactic and chemotropic reactions.

(4) The larva can detect roots or twigs from a distance of about 40 cm., and it can distinguish between the odour of various plants.

(5) Of various fruit trees, the odour of stone fruit was most attractive, and of these, almond comes first and apricots second.

(6) After the larva has located the root, and moulted, the sense of smell weakens gradually until it disappears. A comparative morphological examination of the antennae of neonate and mature larvae shows the olfactory organs are not present in the latter, while distinctly developed in the former.

(7) The larva feeds on the bark, tearing off minute particles, which it chews and finally discards.

(8) The tearing off of the fibres is facilitated by a fluid secreted from the mouth of the larva which softens the wood.

(9) Physiological tests show this fluid to contain a cellulose, a pectinase and an amylase.

(10) Development from hatching to pupation at 33° C. lasts about 60 days, at 27° C. about 100 days.

(11) From empiric data it is apparent that the threshold of development is about 18° C.

(12) From measurements and calculations according to the law of Dyar, the larva must moult at least nine times before pupating.

(13) The larvae resist temperatures above 42° C. for eight hours, but die after a few days in such temperatures.

(14) Practical considerations for the fruit grower based upon this study are presented.