COMPARATIVE MORPHOLOGY OF THE ABDOMEN OF A MACHILID AND A RHAPHIDIID i

The present study deals with the external structure and the musculature of the abdomen of two morphologically important species of insects, Neomachilis halophilis Silvestri (Thysanura) and ?guila adnixa (Hagen) (Neuroptera). The musculature of pregenital segments in the order Thysanura and Neuroptera has been poorly understood. No comprehensive study of the musculature of pregenital segments of the Thy sanura has ever been undertaken, in spite of the fact that many workers studied the ventral appendages of the abdomen of this order. In Neuroptera there have been only two works treating the musculature of pregenital segments (Miller 1933, Maki 1936). Thus, our concept of the generalized musculature of pre genital abdominal segments in insects is based on insufficient knowledge of these two important orders, as was deplored by Snodgrass (1931). As to the morphology of genital segments of pterygote insects, the genitalia of orthopteroid insects has been extensively studied by many workers. Relatively little morphological work, how ever, has been done on genital segments of neuropteroid insects. It was Michener (1944) who first tried to homologize the male genitalia of a neuropteran insect, ?guila, directly with that of Thysanura on the basis of external structures. Gustaf son (1950) interpreted the genital structure of Thysanura quite differently from other workers. It seems, therefore, worthwhile to compare the genital structures of these two morphologically important species on the basis of musculature.