DESCRIPTION OF THE RETROCEREBRAL COMPLEX IN THE ADULT MIDGE, CHIRONOMUS-RIPARIUS (DIPTERA-CHIRONOMIDAE), AND A COMPARISON WITH THAT OF THE LARVA

The retrocerebral complex of Chironomus riparius Meigen consists of both nervous and endocrine structures. The hypocerebral ganglion of the adult is composed of about 20 cells and its anterior part is intimately associated with the aorta. In the larva the ganglion consists of about 6 cells. The nervi corporis cardiaci (NCC) of which there are two pairs in the adult and one pair in the larva run through or around the ganglion before entering the region of the corpora cardiaca. Some of the cardiacal cells contain PAF-positive material in adults but not larvae. The corpora allata are spherical or ovoid and of the pseudolymphoid type. Peritracheal tissue is associated with the nervi corporis allati in both larvae and neoimaginal adults. Postcerebral glands, structures apparently unique to chironomids, are annucleate in adults but granular material accumulates within them during adult life. It is suggested that the retrocerebral complex of C. riparius is unusually simple, that the difference between larvae and adults can be attributed to the absence of feeding in the adults, and that the postcerebral glands may be homologous with the pericardial cells associated with the retrocerebral complex in mosquitoes. Furthermore, the nature of the chironomid system suggests that the X-cells of the gland complex in mosquitoes may represent the intrinsic glandular cells of the corpora cardiaca of other insects. © 1979 Springer-Verlag.