Variation in Habrobracon juglandis ovariole number. I. Ovariole number increase induced by extended cold shock of fourth-instar larvae.

Variation from zero to five ovarioles in the braconid wasp, Habrobracon juglandis, is reported for dissections of females from laboratory stocks. Four ovarioles (two per ovary) is the standard phenotype for the species. Storage of fourth-instar larvar in a refrigerator resulted in a large proportion of females with an increased number of ovarioles (5-11). A 1- to 2-week cold exposure during the period of ovarian differentiation is required for the maximum effect.