The potential contributions of B vitamins by a yeast associate to the nutrition of the carpenter ant Camponotus vicinus Mayr was examined as part of an effort to develop a chemically defined diet. This diet was used to test the effects of individual B vitamin and other nutrient deletions on larval development. The chemically defined diet contained amino acids, vitamins, minerals, and other growth factors in a liquid sucrose matrix. C. vicinus worker colonies with third- and fourth-instar larvae were fed a complete artificial diet or that diet with a component deleted for a 12-wk period. There was a significant effect of diet on larval growth and number of adult worker ants produced in the overall nutrient deletion test, but ant development was often better on incomplete diets with one B vitamin deleted compared with the complete holidic basal diet. Thiamine deletion resulted in significantly higher brood weights compared with the complete diet. Diets of sugar water plus all B vitamins, sugar water only, or a diet minus all B vitamins and cholesterol were associated with significantly lower brood weights. Significantly more adult worker ants were produced by worker colonies fed diets minus cholesterol, choline, thiamine, or riboflavin compared with the complete basal diet. The results suggest that the diet, while suitable for rearing, could benefit from further study to better define component levels. The potential relationship of C. vicinus with yeast associates is discussed in relation to further studies.