62 Psyche [June 



of the Trichoptera and Lepidoptera appear to merge in a single line 

 as we trace them back to this common point of origin. 



The mesothoracic terga and wing bases of tipulid Diptera and 

 the Biiiacns-Whe^ Mecoptera are strikingly similar (Figs. 3 and 6). 

 In both of these types of insects, the mesothoracic terga become 

 very elongate, and the wing bases become shifted backward by 

 the elongation of the prescutal region "psc" (Figs. 3 and 6). The 

 wing bases are also rather narrow or constricted in these insects, 

 as is indicated by the extent of the broad black line bordering the 

 cut off wings in Figs. 3 and 6. A similar tendency is shown in the 

 Neuropteron depicted in Fig. 5,. and it is quite possible that the 

 nemopterid Neuroptera resemble the common ancestors of Mecop- 

 tera and Diptera in some respects, especially in the evident tend- 

 ency toward the elongation of the head region and the reduction 

 of the hind wings to narrow ribbon-like structures, which is carried 

 still further in the Diptera. The outline of the scutellum "si" is 

 very similar in the Dipteron and Mecopteron shown in Figs. 3 

 and 6, and the bulging region bearing the label "psl" in Fig, 3 

 apparently corresponds to the median region labeled "mt" in 

 Fig. 6. The sclerites designated as "prt" in Fig. 3 probably cor- 

 respond to those bearing the same label in Fig. 6. The prescutal 

 region "psc" tends to assume a similar outline in both insects, the 

 tegula "t" is small in both, and the alar ossicle "n" is not greatly 

 developed in either of these insects. The outline of the tergum, 

 and the nature of the wing bases as well as the features mentioned 

 above would indicate a close relationship between the tipulid Dip- 

 tera and the Bittacus-\\\ie Mecoptera, and this is borne out by 

 the nature of the head, antennte, mouthparts, legs genitalia and 

 character of the abdomen in the two groups, so that the marked 

 similarity in appearance between Bittacus and the lower Diptera 

 is not merely a superficial resemblance, but extends to the more 

 minute details as well. I would therefore maintain that the lines 

 of development of the Mecoptera and Diptera merge as we trace 

 them back to their common origin, and the Neuroptera appear to 

 be as much like the common stock "as any other insects, from which 

 the lines of development of the Trichoptera and Lepidoptera, and 

 the Mecoptera and Diptera, have sprung. 



The tergum of the Hymenoptera (Fig. 1) is as much like that of 

 the Neuroptera (Fig. 5) as any, and in general, the Hymenoptera 



