Deficiency in antennae, in external genitalia, or in digestive tract rarely occurs in normal stocks of the parasitic wasp, H. juglandis. In 1 abnormal stock deficient genitalia were associated with deficient digestive tract, and there were many immature deaths. Incidence of trait gradually increased and was maintained by selection, but rarely affected 50% of a fraternity. In another abnormal stock, deficient genitalia and deficient antennae occurred. There was much 9 sterility. Fraternities fell into 2 groups, one averaging 2.6% deficient, the other 45.8. Percentage of deficiency varies according to age of mother, increasing up to 10th or 14th day of adult life and then decreasing. This effect of age of mother may be due to change in yolk of eggs or in food of larvae (influenced by fluid injected at time of stinging caterpillars). Since the trait is genetically complex, linkage variation correlated with age is suggested. Comparable variation is shown in linkage of a lethal with orange eye locus.