Several areas of the bionomics of Culicoides in Virginia were given preliminary investigation. These included surveys for larval habitats, colonization attempts with Culicoides guttipennis (Coq.), host preference studies and adult activity studies. Breeding sites of 22 species of Culicoides were located and briefly described. Samples of mud, debris, etc. from suspected breeding sites were brought into the laboratory and maintained at 70°F in food containers with screened tops. Most species were found to prefer a specific type of habitat (i. e. tree-holes, polluted areas, etc.) but exceptions were occasionally observed. Colonization attempts with C. guttipennis have resulted in the successful establishment of this species in the laboratory. The colony has been maintained for 12-15 generations and is currently producing over 1,000 adults per day and an excess of eggs. Techniques developed for larval and adult maintenance have proved to be highly successful in recent months. Adults were held in a constant temperature cabinet at 80°F ± 2° and 85% relative humidity ± 10% in semi-darkness (less than 1 ft-c ). Eggs were collected on moist filter paper exposed in shell vials. Fly eggs hatched in 3 days and the young larvae were introduced into aquaria containing leaf mold from hardwood forests and distilled water. Larvae pupated in about 12 days and adults emerged about 3 days later. The adult diet consisted of rabbit blood, raisins, sugar cubes, honey water and a 6:6:1:13 mixture of powdered milk, sugar, egg solids and water administered in capillary tubes. In host preference studies 15 species of Culicoides were collected on 1 or more of 14 different hosts used in animal-baited traps. Animals were restrained and exposed on a small platform. After 15 min the animals were covered with a collecting cage. Flies were aspirated from the traps and killed in 70% ethanol. Even though some preferences possibly were shown by some species, more data will be needed before definite conclusions can be drawn. In adult activity studies, most species appeared to be more abundant from 9 PM to 3 AM as indicated by light traps. This was especially noted in C. stellifer, C. haematopotus and C. venustus. The activity of C. haematopotus was fairly constant up to 3 AM and then decreased. C. stellifer and C. venustus activity decreased as the night progressed. / Doctor of Philosophy

The larval and pupal biology of a unique population of gulicoides variipennis inhabiting the brine ponds of Saltville, VA was studied. Developmental threshold temperatures (OC) and thermal constants (Odays) for larvae and pupae were 9.6OC and 387Odays (larval stage) and 9.6OC and 3OOdays (pupal stage) respectively. Accumulated heat units recorded in the field ranged from 366—376Odays between successive generations in the summer. Heat accumulations required for completion of immature development of Q. variipennis were found to be much greater (83lOdays) for the overwintering generation. During the summer, larval/pupal distribution within the littoral zone of a brine pond was confined to the surface cm of mud at or near the shoreline. Insects overwintered farther offshore, mostly as 3rd instars. In ear1y' March, most larvae had xnolted to 4th instars and migrated above shoreline to pupate. Adult emergence occurred in April. Three summer generations were documented for 1983-1984 at Saltville._ Life tables and survivorship curves were calculated for the overwintering generation and the first summer generations for 1983 and 1984. For the overwintering generation, there was a relatively constant mortality rate between successive ageclasses (Type II survivorship curve). During the summer, there was relatively little mortality between successive larval age—classes but a dramatic increase in mortality was evident at the pupal stage (Type I survivorship curve). Late instar larvae were found to migrate from the shoreline onto the exposed mudflats to pupate, thus becoming vulnerable to predation by ants and carabid beetles. Excellent survival rates of the larvae during the summer was attributed to habitat stability, the paucity of predators and parasites and abundant microfloral content (i.e. food} of the pond water. Intra-specific competition for food resources appeared to be alleviated somewhat by partitioning of those resources on a diurnal cycle. / Ph. D.