The spectral sensitivities of the dorsal ocelli of cockroaches (Periplaneta americana, Blaberus craniifer) and worker honeybees (Apis mellifera) have been measured by electrophysiological methods. The relative numbers of quanta necessary to produce a constant size electrical response in the ocellus were measured at various wave lengths between 302 and 623 mµ.
The wave form of the electrical response (ERG) of the dark-adapted roach ocellus depends on the intensity but not the wave length of the stimulating light. The roach ocellus appears to possess a single photoreceptor type, maximally sensitive about 500 mµ.
The ERG's of bee ocelli are qualitatively different in the ultraviolet and visible regions of the spectrum. The bee ocellus has two types of photoreceptor, maximally sensitive at 490 mµ and at about 335 to 340 mµ.
The spectral absorption of the ocellar cornea of Blaberus craniifer was measured. There is no significant absorption between 350 and 700 mµ.