An unusual type of corneal nipple in the earwig, forficula sp., with a possible anti-reflection role

Abstract

An unusual type of corneal nipple pattern, with features different from the usual lower height (Group I) and greater height (Group II and III) nipples, has been detected in the corneal surface of the earwig, Forficula sp. However, the nipples show some similarities with each of the two above types possessing certain characters. The height of the nipples, their shape and arrangement in the facet suggest that the nipples may act as an anti-reflection device, and thus increase the intensity of transmitted light, thereby aiding scotopic vision of the insect.