The Postembryonic Development of the Compound Eye and Optic Ganglia in Dragonflies

After a histological examination of the compound eye and optic ganglia of several dragonfly nymphal instars (with particular attention given to the last nymphal instar), several observations relative to the postembryonic development of these structures are noted. The nymphal dragonfly compound eye increases in size from instar to instar by the development of new ommatidia from a permanent primitive portion of eye tissue located on the median edge of the original nymphal eye as well as from individual ommatidial growth. Internally adjacent to this zone of developing ommatidial tissue, a portion of the first optic ganglion is also in a constant state of development. The adult dragonfly eye is largely a new structure which develops during the last nymphal instar from primitive anlagen located outside, but connected to the functional nymphal eye. The adult optic ganglia also develop in the last nymphal instar. Development proceeds in two distinct regions, one region giving rise to that portion of the adult ganglion which is found adjacent to the dorsal ommatidia, and the other region giving rise to that portion of the adult ganglion which lies adjacent to the ventral ommatidia