TAXONOMICAL AND BIOLOGICAL STUDIES OF A NEW MAN-BITING SUBGENUS OF FORCIPOMYIA (DIPTERA, HELEIDAE)

Abstract

The taxonomy and biology of a new man-biting subgenus and species of Forcipomyia (Dacnoforcipomyia anabaenae) are studied. The systematic position of the fly is discussed and its confusion with many oriental man-biting species of Lasiohelea s. str. from which the female cannot be distinguished, is shown to be in vogue. The separation of the two subgenera will have to depend on the morphology of the immature stages and the male genitalia. The larva lives entirely on a bluegreen alga, Anabaena sp., with which it is constantly associated and from which it is partially or completely concealed by the latter covering its body and spines. Because of this inseparable relationship the duration of the life cycle (averaging about 3 weeks) is proportionally related to the availability of the alga and the size of the early stages and adults is also more or less proportionally related to the amount of food ingested. In its day-biting habit the female resembles Lasiohelea, Leptocenops, Austroconops and Styloconops, showing a biting peak at about 12 noon to 3 p.m. In its feeding habit and in the duration of its life cycle, it resembles Culicoides nubeculoses. In its ovarian cycle it essentially resembles Anopheles maculipennis. Egg development is studies in detail, three morphological phases of growth being distinguishable. The female shows high selective power for oviposition sites and will oviposit only when Anabaena sp. is present, in an undisturbed condition, in an original (native) medium. The flies are found throughout the year, fluctuating in density with the annual rainfall which presumably determines the abundance of the alga on which it is dependent. An attempt to assess the epidemiological significance has not be altogether successful due to the inability to maintain females beyond the two gonotrophic cycles. However, characters for separating nullipars from pars have successfully established. Control measures are suggested from a knowledge of the biology.