Formation of Salivary Secretion in Rhynchosciara Americana

INTRODUCTION Since the genus Rhynchosciara belongs, like Chironomus, to the suborder Nematocera it will be very interesting to see if the formation of its salivary secretion proteins is similar to that of Chironomus secretion or to Bombyx silk biosynthesis . Moreover, this work will be of importance for a better understanding of the hemolymph protein function and will provide a basis for improving the physiological study of Rhynchosciara salivary glands which are used in gene action studies . The salivary glands of Diptera are organs homologous to the silk glands of Lepidoptera, in that both are labial glands (1) . Larvae of several Chironomus species produce a salivary secretion which, according to its properties (2), fits the silk definition given by Rudall and Kenchington (3) . Formation of Diptera salivary secretion has been investigated in some species of Chironomus (4, 5, 6) . The results obtained indicate that the proteins present in the salivary secretion are in part synthesized by the salivary gland and in part sequestered from the hemolymph. However, this conclusion is not fully accepted (7) . We have studied the origin of the salivary secretion proteins of Rhynchosciara americana' larvae . These larvae produce a salivary secretion that is used in spinning a communal cocoon, inside of which the fourth instar larvae undergoes pupation and where development goes on until the emergence of the imago . The R. americana communal cocoon is made of threads and plaques of a highly insoluble material which shows characteristics of a true silk . METHODS