Phenology of Stomoxyinae in a Kenyan forest

The biology of nineteen taxa of African Stomoxyinae was studied during experiments with odour-baited Vavoua traps in Nairobi National Park, Kenya. Both male and female Stomoxys were captured in similar numbers with CO2 released at 2 l/min or octenol released at 2 mg/h. Some species of Haematobosca reacted synergistically to a combination of these attractants, producing large increases in catch. Stygeromyia and Rhinomusca responded only to CO2 and Prostomoxys did not respond to either bait. Many different activity patterns were documented in these genera, but most activity was concentrated just prior to sunset. For example, at peak densities nearly 1500 Stomoxyinae representing fourteen taxa were caught in a single trap between 18.00 and 19.00 hours. The Stomoxyinae community was exceptionally diverse when compared with other biting fly communities. Using data from traps set with different odour baits in the park forest, Shannon-Wiener diversity indices (H') varied from 2.5 to 2.8, and evenness (J') varied between 0.61 and 0.68. The Stomoxys population was extremely female-biased at the start of the rainy season, with species such as S. inornatus and S. boueti consisting of nearly 100% females. Sex ratios equalized when the first rainy-season generation emerged. population doubling times estimated from trap indices were approximately 12-16 days in two habitats (forest and riverine woodland).