Vertebrate host specificity of wild-caught blackflies revealed by mitochondrial DNA in blood.

Blood-feeding blackflies (Diptera: Simuliidae) transmit pathogens, harass vertebrate hosts and may cause lethal injuries in attacked victims, but with traditional methods it has proved difficult to identify their hosts. By matching mitochondrial DNA (mtDNA) sequences in blood collected from engorged blackflies with stored sequences in the GenBank database, relationships between 17 blackfly species and 25 species of vertebrate hosts were revealed. Our results demonstrate a predominance of large hosts and marked discrimination between blackflies using either avian or mammalian hosts. Such information is of vital interest in studies of disease transmission, coevolutionary relationships, population ecology and wildlife management.

Testing hypotheses on egg number and size in black flies (Diptera: Simuliidae).

Field-collected gravid females were used to test a series of inter- and intraspecific hypotheses on egg size and number in 23 species of black flies. Qualitative differences between bird and mammal blood did not result in significant differences with respect to fecundity properties. The five species with overwintering larvae produced more eggs than did the 18 species with overwintering eggs. Contrary to prediction, egg size was correlated significantly with body size in only two of 17 examined species; indeed, in three species this relationship was negative. However, the association between female size and egg number within species was positive. Strong support was found for a tradeoff between egg size and number across species but not within species. The present study shows similarities with other dipterans but also substantial variability, probably reflecting a high degree of flexibility. The results are primarily discussed in an evolutionary context, but they also provide useful information for black fly management.