Abstract
The observations were made on the bionomics of larvae and on the blood-sucking behaviour of adults of the deerfly, Chrysops suavis Loew, in Kozu pasture in Gunma Prefecture. Most of the larvae of Chrysops suavis were found in 5cm depth from the sandy soil surface in an artifitial pond and usually 40cm apart from the edge of the waterbody. No larva found in swamps or streams in the pasture. Its pupal period on an average, was 10.13±2.76 days. It took roughly 1 to 2 minutes for the molting of pupae. The emargence took place during 9 to 11 a.m. and 3 to 5 p.m. in many cases. The diurnal rhythm of blood-sucking activity of Chrysops suavis apparently had two distinct peaks, one in the morning and the other in late afternoon, as shown by the number of flies on cattle hosts. The adults of Chrysops suavis attack mainly on the scrota of the ox and the horse. The adults attack neither on the back nor the side of the animals.
