Quarterly Journal of Microscopical Science, Vol s3-100, 65-71, Copyright © 1959 by Company of Biologists

The Function of Chromatocytes in the Simuliidae, with Notes on their Behaviour at the Pupal-adult Moult

¹ Department of Zoology, University of Bristol

In the larvae and pupae of the Simuliidae the cuticle and epidermis of the thorax and abdomen are more or less transparent, and the colour pattern is formed by cells (chromatocytes) that contain pigment granules., These cells always lie below the basement membrane. It is possible to photograph the chromatocytes without damage to the animal and thus to make photographic records of the behaviour of particular chromatocytes over a period of many days when the animal is moving about and feeding in the normal way.

The chromatocytes accumulate lipids. The accumulation of lipids during larval growth and their depletion during adult development has been photographed in normal undamaged animals.

Conspicuous changes in the colour pattern, especially of the thorax, occur at metamorphosis. Such changes are due to mass migrations and the formation of new aggregation patterns by the chromatocytes. While such movements of the chromatocytes are taking place in some parts of the body, the aggregation patterns of chromatocytes in other parts of the body remain unchanged and appear to be unaffected by the events that initiate and accompany moults and ecdyses.