The ovarian cycle and egg stage in Leptoconops (Holoconops) becquaerti (Kieff.) (Diptera, Ceratopogonidae)

Abstract

Leptoconops becquaerti (Kieff.) is one of the most troublesome species of biting midge in Jamaica. The gonotrophic cycle in this insect was studied and is described. In this species a single blood-meal is sufficient for the development of the ovaries and the maturation of eggs.The stages in follicle development and digestion of the blood-meal adopted for other blood-sucking Diptera have been applied to L. becquaerti with slight modifications. A high degree of gonotrophic harmony is present in this insect.Fully fed females were kept at five temperatures, 68, 77, 85, 91 and 98°F., to determine the time taken for the ovarian follicles to reach Stage V of development (egg mature, chorion present). The times were approximately 98, 64, 36, 30 and 27 hours, respectively.It was demonstrated that the number of ovarioles in L. becquaerti was proportional to the size of the individual (as measured by wing length). The average number of ovarioles in an insect of wing length 0.83 mm. (the mean wing length of the population sampled) was about 103.The number of eggs matured was also proportional to wing length, and was also dependent upon the temperature at which the flies were kept. Thus at the standard wing length of 0·83 mm., the average numbers of eggs matured at the five chosen temperatures (68 to 98°F.) were 78, 85, 65, 61 and 60, respectively. Females that had matured eggs were induced to oviposit by the decapitation technique.Females provided with a source of carbohydrate (honey) during egg maturation produced slightly more eggs on the average than those fed on blood alone. The comparable figures at 91°F. in the standard individual were 65 and 61, respectively. The probable rôle of supplementary carbohydrate feeding in nature is discussed.At the five experimental temperatures the greatest number of eggs hatched on days 11, 7, 5, 4 and 4, respectively, after laying. Egg-batches used in these experiments were deposited by decapitated females, and may therefore have been laid somewhat before the usual time in nature. The percentage fertility varied between individual batches at all temperatures, but the over-all fertility was consistently high (70–75%) at the lower four temperatures, and very low (4%) at 98°F. This difference almost certainly resulted from high temperature in the latter instance. Fertility in egg-batches deposited naturally (without decapitation) was of the same order as that in batches deposited by headless females.