Studies of winds and weather during migrations of Simulium damnosum Theobald (Diptera: Simuliidae) , the vector of onchocerciasis in west Africa
Magor, JI.; Rosenberg, LJ.
Bulletin of Entomological Research 704: 693-716
ISSN/ISBN: 0007-4853 DOI: 10.1017/s0007485300007987
Reports of the presence and absence of biting by S. damnosum Theo. in the Volta River Basin in 1962, 1966 and 1975 were used to identify occasions when sites were invaded by parous and nulliparous females. Circumstantial evidence suggests that this insect is a wind-borne migrant, and the weather before and during some of these invasions was examined. Although most invasions studied took place south of the Inter-tropical Convergence Zone, evidence is presented for the first time suggesting that migration also takes place to the north of this zone. Immigrants were captured at the invaded sites only when light winds or calms were present. This cannot be used as proof that S. damnosum migrates and lands only where winds are light or it is calm because host-seeking is inhibited by high winds and the time of arrival, as opposed to capture on a host, is unknown. Until the factors initiating emigration, as well as the height, duration and number of flights in each gonotrophic cycle and the time of immigration are known, the present findings cannot be tested rigorously nor can wind records be used to trace the source of immigrants.