Abstract
Colonizing order of the blackfly species and voltinism of Mayacnephia aguirrei were studied in seasonal streams in an onchocerciasis-endemic area of Guatemala. Mayacnephia aguirrei colonized first, then Simulium metallicum, S. horacioi and S. ochraceum appeared, followed by S. callidum and S. (Hemicnetha) spp. The colonizing order of these species coincided with the order of a preference for stream discharge from small to large. Mayacnephia aguirrei had at least three generations in a year.