The Ocelli in Insects

Abstract

AT vol. xiii, p. 168, H. Müller calls the attention of entomologists to a subject which has interested other entomologists before—the function of the ocelli in insects. With due deference to a suggestion made by such an authority, it seems to me that the size of the ocelli in hymenopterous insects is not dependent on their nocturnal habits. Why in hymenoptera more than in other orders? Indeed, it may be doubted whether in some insects the ocelli are organs of vision at all, or at least whether they are of any practical use as such in the imago. Their number, as well as size, differs in different species of the same, order, seemingly without regard to their habits, whether diurnal or nocturnal, and in many moths they are so completely concealed by the scales that it is necessary to divide the head to ascertain whether they are present or absent, so that it is difficult to understand how they can be of any service as organs of vision. May they not in the imago, in such cases, be merely functional remnants of larval organisations.