G. C. CRAMPTON 219 



Only the more important parts of the genitaHa have been 

 described and homologized in the present paper, since I am 

 hoping to make a more detailed studj^ of the genitalia of the 

 Diptera later, and it has seemed preferal)le to present the essen- 

 tial facts in a preliminary paper, to serve as the basis of the more 

 detailed study of the parts, and to call attention to the misin- 

 terpretation of the parts by recent investigators, since errors 

 once established, are extremely difficult to eradicate. If such 

 errors go unchallenged, they may be accepted as correct by 

 those who have not the time or the inclination to investigate 

 the matter for themselves. It is a very hopeful sign, however, 

 that even in systematic entomology, those who describe mor- 

 phological parts are l^eginning to be critical as to the correctness 

 of the homologies indicated by the terms used, and it is to be 

 hoped that the modern spirit of scientific exactness manifested 

 in verteljrate osteology and kindred subjects, will eventually 

 assert itself in entomological terminology, as it has long since 

 done in the realm of vertebrate anatomy. However, until the 

 students of insect morphology have worked out the homologies 

 of the various structures throughout the orders of insects (as 

 has ])een done by Comstock and his associates for the wing 

 veins of insects) the systematists can hardly be blamed for using 

 the mostconvenient terms (regardless of their correctness) in 

 the particular groups in which they are working! 



The parts of male Mecoptera have not been discussed in 

 detail in the present paper, since the labelling of the figures will 

 serve to indicate the homologies of the structures in question. 

 I would call attention, however, to the fact that the genitalia 

 of the Bittacus-gYoup are very different from those of the Panorpa- 

 group, and the genitalia of Merope are quite different from either, 

 although Merope approaches more closely to the Panorpn-gvo\\\) 

 than to the Bittacus group, as was shown in previous papers 

 dealing with these insects. Such of the parts of the genitalia 

 of the male Diptera (with the Mecoptera) as were not discussed 

 in this paper, ma}' be determined by referring to the labels of 

 the figures, and tracing the same labels through the series, to 

 the fundamental i)lan of the genitalia of insects in general given 

 in figure 4. 



TRANS. AM. KNT. SOC, XLVIII. 



