The Components of the Visual System of a Dragonfly.

In this study of the electroretinograms of dragonflies (adults and nymphs) the objectives were to determine the number of classes of photoreceptors present in the visual system and to allocate these to particular morphological regions. There are probably five classes of photoreceptors present with peak sensitivities near 550, 530, 518, 420, and < 380 mmicro. The dorsal ocelli contain two classes (518 mmicro and < 380 mmicro). The ventral (anterior) ommatidia of the adult compound eye contain at least two classes (near 518 mmicro and < 380 mmicro) and probably a third class (near 550 mmicro). The dorsal ommatidia of the adult compound eye contain one class (420 mmicro) and possibly another class (< 380 mmicro). The compound eye of the nymph contains one class (530 mmicro) and possibly another class (420 mmicro).