The thermal constant of the onchocerciasis vector Simulium damnosum s.l. in West Africa.

The minimum water temperature for development (t(0)) and the thermal constant (K) for the development of immature stages of Simulium damnosum s.l. (Diptera: Simuliidae) in West Africa were estimated as 20.1 °C and 93 day-degrees, respectively, based on analyses of published data on development rates of eggs, larvae and pupae at different water temperatures (24.0 °C and 31.5 °C). Thus, at a constant water temperature of 30.0 °C (approximately 10 °C above t(0)), adult flies would emerge about 9 days after oviposition. Analysis of a dataset probably restricted to S. damnosum s.s., but for which the temperature for the egg stage varied, revealed a much lower t(0) (16.3 °C) and a much higher K (181 day-degrees), suggesting that the insects' thermal relations may be cytoform-specific. The results will aid control decisions and predictions of possible effects of climate change on sizes and geographic distributions of populations of onchocerciasis vectors in West Africa.