A simple method for culturing Culicoides nubeculosus (Mg.) in the laboratory is described, the medium used for rearing the larvae being a mixture of powdered mud from near a farm byre, dried autolyzed yeast and powdered charcoal, in the proportions 25:3:2. A layer of the mixture 4 mm. deep was spread over the bottom of unglazed earthenware pots, 6 in. diam. x 1 in. high, and just covered with water. After about three weeks in an insect-proof cage in the open, the pots were brought into the laboratory, the temperature of which was maintained at 20°C. except for brief periods in very hot or very cold weather. Each pot was stocked with from 70 to 220 newly hatched larvae, derived from a single batch of eggs laid on moist filter-paper discs in 3 x 1-inch glass mating tubes by adults that had been fed on human blood and provided with raisins. The surface of the medium became covered with a growth of bacteria, algae, fungi, and protozoa, which provided a source of food for the larvae. These made shallow burrows in the substratum from which they partially emerged to feed and in which they pupated. About 45 per cent, of those introduced emerged successfully as adults.

The incubation and pupal periods lasted 3–6 and about 4–7 days, respectively. The time taken for larval development varied greatly between individuals from the same batch of eggs, and also between batches started at different times of year. The complete life-cycle of examples started as larvae in January–September was thus 3–8½ weeks, the period over which emergence occurred amongst a single batch being 1–5 weeks; the corresponding figures for those started as larvae in October were 6–18 and 2 to nearly 12 weeks.

The behaviour in the various stages is briefly described.