Evolution and Specializations of Insect Eyes: Twisted‐Wing Insects and Larval Diving Beetles.

Abstract

Although most insects have compound eyes, considerable variation has evolved among their visual systems. Here I present two examples of insect eyes for which anatomical characteristics provided important clues to their functional organization. In adult male Strepsiptera large lenses and cup shaped retinae suggested the presence of small image‐forming eyes in place of ommatidia that otherwise are observed in compound eyes. Behavioral tests of the spatial resolution confirmed increased image resolution of these “eyelets”. The bizarre tubular eyes of diving beetle larvae serve as another example: here, multiple linear retinae pointed to the possibility that these eyes may be used to scan the environment. Behavioral tests showed that this indeed is the case. Moreover the ultrastructural organization of microvilli within its UV‐sensitive distal retina implied that these cells could be polarization sensitive, a functional characteristic that we have confirmed physiologically. Although most insect eyes fall into a few well‐characterized categories, anatomical studies of highly unusual eyes continue to point towards interesting novel functional organizations of visual systems. This research is supported by the National Science Foundation.