Extraocular photoreceptors in the brain of Epilachna varivestis (Coleoptera, Coccinellidae).

Within the optic lobe of adult Mexican bean beetles, Epilachna varivestis, three complex areas were detected that display elements with the morphological appearance of photoreceptors. Each of these complexes contains about eight cells that show fully differentiated rhabdomeres, screening pigments and other features typical of photoreceptors. It was shown that these areas originate from larval stemmata, which move into the depth of the head capsule during metamorphosis and are finally embraced by the outgrowing optic lobes. Although the function of these formations is not yet known, there are some indications that they may play a role in the entrainment of circadian clocks.