The ovarian cycle in Culicoides barbosai Wirth & Blanton and C. furens (Poey), two biting midges of considerable importance in Jamaica, was studied in the laboratory. In C. furens, a single blood-meal was sufficient for development of a substantial number of eggs; in C. barbosai, which took a relatively smaller blood-meal, very few eggs were matured (usually between 10 and 20 but sometimes fewer than 10), and some females failed to produce any eggs at all.

A high degree of gonotrophic harmony was observed in C. furens, but in C. barbosai the degree of harmony was low and a large proportion of the ovarian follicles degenerated; these differences may be associated with the relative size of the blood-meals of the two species.

The duration of the gonotrophic cycle (from feeding to the appearance of mature eggs in the ovaries) at 68, 77, 85 and 91°F. was 156, 104, 82 and 72 hr., respectively, in C. barbosai and 102, 59, 42 and 36 hr. in C. furens.

In experiments on the effect of temperature and carbohydrate feeding on egg production, temperature did not influence egg production in C. barbosai, and greater numbers of eggs were not matured by females given access to honey during the period of egg development. However, access to honey did increse the proportion of individuals surviving the period of egg maturation and also the numbers that mastured any eggs at all. Females of C. furens kept at 77°F. matured more eggs than those kept at 91 or 85°F.; access to honey improved survival, but its effects on egg production were inconclusive in these experiments.

Observations indicated that adults of both species are probably in the habit of taking carbohydrate food in nature.

Females of both species may be autogenous, though the proportion of such individuals varied considerably between populations from different breeding sites. Autogenous females of both species emerged from the pupa with ovaries already relatively well developed; in C. barbosai the ovarian follicles were in Stage IIB or III, in C. furens they were in late Stage IIA or IIB. Large numbers of eggs were matured by autogenous females of the former, and the same is probably true of the latter.

The egg stage is apparently of longer duration C. barbosai than in C. furens. At 68, 77, 85 and 91°F., most eggs of C. barbosai hatched on days 12, 6–7, 5–6 and 5, respectively, whereas at the three higher temperatures most eggs of C. furens hatched on days 4, 3 and 2. Percentage fertility varied between individual egg batches of both species.