This paper presents a key to the larvae and pupae of 28 species of Culicoides found in Britain and to larvae and pupae of the genera Stilobezzia, Serromyia and Ceratopogon including the subgenera Ceratopogon and Isohelea. The keys are supplemented by descriptions of the larvae and pupae, including photographs of the fourth instars and figures of the so-called “hypopharynx” —the true epipharynx—of most of the larvae and by figures of specific characters of the pupae. Twenty-eight species of Culicoides larvae are described:—C. albicans, C. chiopterus, C. circumscriptus, C. cubitalis, C. cunctans, C. delta, C. fascipennis, C. grisescens, C. halophilus, C. heliophilus, C. impunctatus, C. lupicaris, C. maritimus, C. nubeculosus, C. obsoletus, C. odibilis, C. pcdlidicornis, C. pictipennis, C. pseudochiopterus, C. pulicaris, C. punctatus, C. riethi, C. salinarius, C. scoticus, C. simulator, C. stigma, C. truncorum, and C. vexans. The descriptions of the pupae include all the above, with the addition of C. parroti.

An analysis has been made of the breeding preferences of Culicoides and it was found that species could be placed in one of six groups depending on the larval habitat. The six categories were:— (i) Bog, (ii) Fresh Water Marsh, (iii) Swamp, (iv) Mud, (v) Salt Water Marsh and (vi) Dung.

The vertical distributions of seven species of Culicoides larvae are given. There are marked differences between the species in this respect.

The course of embryonic development of S. gregaria under controlled conditions of temperature and humidity is described, with special attention to the water requirements of the developing egg. The development of the egg is interrupted if contact water is lacking and is resumed when the egg is moistened. This occurs at the stage of late anatrepsis, which is the stage at which the embryo of some other locusts and grasshoppers undergoes diapause.

During a study of the natural enemies of mealybugs that transmit a virus causing swollen shoot disease of cacao, R. G. Donald submitted specimens representing a new species of the gall midge genus Coccomyza. This species is here described to provide a name for use in connection with the biological work.

The damage caused by the Cotton Jassid to the Egyptian-type cottons in the Gezira and White Nile areas of the Sudan is very considerable. Realisation of this fact has been greatly aided by chemical control of the pest in small-scale experiments, followed by large-scale work with tractor-drawn sprayers and with helicopters fitted with spraying equipment. This paper deals primarily with examination of available records pertaining to the cotton crops in the four seasons from 1946/47 to 1949/50, preceded firstly by an introduction which emphasises the importance of yield records in the appraisal and interpretation of losses from pests, and secondly by an account of certain aspects of the pest in the Gezira Scheme.

Large-scale spraying to control the pest started in the Gezira in the crop season 1945/46; yield increases from about 1,250 feddans (acres) sprayed with 0·1 per cent. DDT emulsion were very satisfactory. In succeeding seasons increasing areas were sprayed; in 1947/48 spraying was extended to the cotton farms along the White Nile between Khartoum and Kosti; in 1949/50 the total area sprayed in the Sudan was over 150,000 feddans. Material and also methods and dates of application varied considerably.

An account is given of an investigation made of the life-histories of Oscinella frit and its parasites in Ontario, Canada, with a view to the possible introduction of suitable parasites into England. The various Chloropid species associated with O. frit in North America are discussed.

The life-history of the frit-fly in Ontario is similar to that in England except wheat, not oats, is attacked, and that there appears to be no regular grain-infesting generation, but the insect is never a major pest in Canada.

The life-histories of the following six species of parasites are described : Hexacola sp. n., Polyscelis sp. n., Loxotropa sp., Cyrtogaster sp., Callitula bicolor and Spalangia drosophilae. Other hosts from which these parasites have been reared include Chloropids associated with O. frit in wheat, namely O. carbonaria, O. soror, O. minor and Meromyza americana.

A brief account is given of the control exerted by these parasites on the population of frit-fly in Ontario and a comparison is made between the Canadian and English parasite complexes. From this it is concluded that S. drosophilae might exert some control of frit-fly if introduced into England.

All the leaf-feeding sawflies on Larix in Britain belong to the Nematine Tenthredinidae. Up till a few years ago, the most notorious recorded in this country was Pristiphora erichsonii (Hartig), though local attack of P. wesmaeli (Tischbein) and P. laricis (Hartig) have also occured. These are also the chief Tenthredinid enemies of larch on the European continent, where the genus Anoplonyx has apparently never occured in sufficiently large numbers to cause economic damage. In Britain, where larch is not a native tree, the sawflies attacking its leaves are all restricted to it and so must have been introduced into the country.