Annals of Tropical Medicine & Parasitology, Vol. 92, No. 8, 869±876 (1998) Behaviour of Lutzomyia longipalpis in an area of southern Honduras endemic for visceral/atypical cutaneous leishmaniasis BY J. CARRASCO* Section of Immunology, Department of Microbiology, Universidad Nacional Autono Âma de Honduras (UNAH), Tegucigalpa, Honduras A. MORRISON Peace Corp, Tegucigalpa, Honduras AND C. PONCE Central Laboratory `Alonso Suazo’, Health Ministry, Tegucigalpa, Honduras Received 23 March 1998, Revised 20 July 1998, Accepted 22 July 1998 The predominant sand¯y in Las Maria de Pavana, Choluteca, Honduras, was found to be Lutzomyia longipalpis , most (69%) of the 791 specimens of this species caught being male. When local Lu. longipalpis were studied over 1 year (1986±1987) using CDC traps, peaks in the size of the adult population were observed in December and July, each after a period of rain. Most [51% (24/47)±67% (97/144)] of the ¯ies caught inside houses were female whereas most [55% (6/11)±56% (37/66)] of those caught outside were male. Far more Lu. longipalpis of both sexes were collected, per h of collection, from cattle and horses than from dogs or pigs, the vast majority (83%±93%) of the ¯ies caught on each type of animal being male. The males may bene®t from resting on the mammals because the females with which they mate come to the same animals for blood. The females may bene®t by the presence of the males, not only by the increased chance of ®nding a mate but also because pheremones from the males may attract the females both to the males and to a bloodmeal source. The adult Lu. longipalpis only appeared to be active during the hours of darkness, none alighting in the twilight of dawn (04.00±06.00 hours) or dusk (18.00±20.00 hours) on the large mammals investigated. Southern Honduras is endemic for Leishmania chagasi, the causal agent of visceral and atypi- cal cutaneous leishmaniasis, and the parasite is transmitted in the area by the sand¯y Lut- zomyia longipalpis (Ponce et al., 1991). Overall, 210 cases of visceral leishmaniasis (VL) were recorded in the area between 1974±1990 and 500 cases of atypical cutaneous leishmaniasis (ACL) between 1990±1991 (Ponce and Ponce, 1993). Apart from a complete epidemiological study (including collections of Lu. longipalpis) carried out between 1975±1983 (Navin et al., 1985), there has been very little investigation of the behaviour of Lu. longipalpis in Hon- duras. Studies in the neighbouring countries of El Salvador (Rosabal and Trejos, 1965) and Costa Rica (Zeledo Ân et al., 1984) indicate that Lu. longipalpis feeds readily on domestic ani- mals such as cows, horses, pigs, dogs and chickens, and that the majority of Lu. longi- palpis collected are males ( . 90% in each case). Although the area of Costa Rica investi- gated by Zeledo Ân et al. (1984) is ecologically similar to southern Honduras, no cases of VL have been reported from Costa Rica. The absence of VL in Costa Rica may perhaps be related to relatively low vasodilatory activity in * E-mail: jcarr@ns.unah.hondunet.net. 0003-4983/98/080869-08 $9.00 Ó 1998 Liverpool School of Tropical Medicine Carfax Publishing Ltd