Seasonal changes in larval populations of Leptoconops becquaerti (Kieff.) (Dipt., Ceratopogonidae) in Jamaica, with observations on the ecology

Seasonal changes in two natural larval populations of Leptoconops becquaerti (Kieff.), a biting sandfly of economic importance in the Caribbean area, are described from studies in 1963–64 near Montego Bay. Aspects of the ecology arising from these observations are included. An attempt is made to relate the seasonal changes in the larval populations to the seasonal distribution of adults, and in addition, a separation is made between the autogenous and anautogenous forms of the insect.Larvae of both autogenous and anautogenous forms lived together in the same breeding sites and did not appear to differ in their spatial distribution. The two populations studied consisted mainly of larvae associated with the small, autogenous form. Drastic reduction in both populations occurred following events such as wave action and heavy rain that had a mechanical action on the sand in which the larvae lived. The distribution of both forms of larvae was dependent upon the surface elevation with respect to the level of free soil water, since this to a large extent, owing to the upward capillary movement of water, governs moisture content of the surface sand. Elevations between about 9 and 17 in. appeared to be the most favourable. Permanent breeding probably does not occur in sand at elevations greater than about 21 in., though temporary breeding may occur at higher elevations if some other source of moisture (e.g., frequent rain) is available.In the autogenous form, a prolonged period was spent in the third larval instar. This was probably induced by some factor associated with lack of moisture in the sand, and appears to be broken (causing completion of development) by an effect of increased moisture content after heavy rain. This phenomenon probably does not occur in the anautogenous form.