The DV/D ratio was measured in about three and a half thousand males of pipiens and quinquefasciatus, mostly from North America. It was found that the average ratio in a collection of pipiens is usually 0.1 or less and in quinquefasciatus 0.6 or more. In individual specimens the ratio is usually less than 0.2 in the former and more than 0.4 in the latter. In North America north of 39°N. only pipiens is usually found; south of 36°N. only quinquefasciatus is generally present. Collections from between these latitudes may contain one or the other form, intermediates, or various mixtures of the three. There seems little doubt but that the forms do hybridize in nature. In some localities (Sacramento, Calif.) intermingling seems to be much freer than in others (East St. Louis, Ill.). At the present time it seems wisest to retain subspecific names for the two forms.