The objective of this project is to gain a sufficient knowledge of the ecology of arboviruses to allow the development of effective disease control programs. A primary focus is to study the genetic and environmental factors that control the competence of mosquitoes to be viral vectors. Present research is on the genetics and physiology of Culex tarsalis with parallel preparations for future field pilot studies on genetic control of this vector. A second focus of concern is on alternative means by which arboviruses overwinter in a temperate area in their basic vertebrate host and vectors. BIBLIOGRAPHIC REFERENCES: Ferguson, J.A., Reeves, W.C. and Hardy, J.L. 1977. Antibody studies in ponies vaccinated with Venezuelan equine encephalomyelites (strain TC-83) and other Alphavirus vaccines. Amer. J. Vet. Res. 38:425-430. Nelson, R.L., Tempelis, C.H., Reeves, W.C. and Milby, M.M. 1976. Relation of mosquito density to bird-mammal feeding ratios of Culex tarsalis in stable traps. Amer. J. Trop. Med. Hyg. 25: 644-654.