Diurnal nectar-feeding of salt marsh Tabanidae (Diptera).

In studies in Connecticut, adults of Chrysops fuliginosus Wied. visited Rosa palustris and Achillea millefolium flowers primarily during the morning (07.00-11.00 h), but following a mid-day lull in their attraction to these plants, a small number of males and females resumed feeding on flowers between 18.00 and 20.00 h. Adults of C. atlanticus Pechuman were sighted on these nectar sources sporadically throughout the day. Anthrone tests showed that females of C. fuliginosus, C. atlanticus and Tabanus nigrovittatus Macq. contained fructose throughout daylight hours. Thin-layer chromatography detected glucose alone or a combination of glucose and fructose in more than 90% of Chrysops spp. tested, whereas a mixture of glucose, fructose and sucrose was found in 51.6% of the females of T. nigrovittatus. Pollen grains of Compositae, Rosaceae, Gramineae, Acer, Quercus or Salix were recovered from digestive tracts in 28% of the 150 flies examined. The presence of common nectar sugars and pollen grains in tabanids suggests an important association between them and host-plants. In addition to carbohydrates, the proteins and amino acids (derived from pollen and nectar) may be important dietary components for adults.