342 Annals Entomological Society of America [Vol. X, 



In some Diptera (Fig. 14) the contour of the upper portion 

 of the 'head is more Hke that of certain Neuroptera (Fig. 4), 

 while in other Diptera (Figs. 6 and 8) it is more like that of 

 certain Mecoptera (Figs. 5 and 9). On the whole, the basal 

 segments of the antennae of the Diptera (Figs. 6 and 14, "a") 

 are more like those of the Mecoptera (Fig. 5), and the 

 resemblance between the antennal segments of the Mecopteron 

 Merope and those of certain Mycetophilids and other Diptera is 

 very striking, as I am hoping to show in a subsequent paper. 

 In these respects, the Trichopteron shown in Fig. 11 is more like 

 the Neuroptera than it is like the Diptera and in general the 

 statement would hold true, that the Mecoptera approach the 

 Dipteron type far more closely than the Trichoptera do, and are 

 therefore in all probability much more closely related to the 

 Diptera than the Trichoptera are, although the Trichoptera also 

 have carried over certain "ancestral" features from the common 

 ancestral group which gave rise both to them and to the 

 Mecoptera and Diptera, so that they cannot be entirely dis- 

 regarded in a phylogenetic study of the insects in question. 



Although the labial palpi '7^" are much larger than the 

 maxillary palpi "m^" in the "long-headed" Neuropteron shown 

 in Fig. 4, the maxillary palpi "w^" are much longer than the 

 labial palpi "/^" in the Neuropteron shown in Fig. 1, and in 

 most Mecoptera (Figs. 2, 5 and 9) and Diptera (Figs. 3 and 14) 

 this is likewise the case, as is also true, to a lesser degree, in the 

 Trichopteron shown in Fig. 11. There is thus apparent in 

 the Mecopteron and Dipteron stocks a marked tendency toward 

 the reduction of the labial palpi, and the glossas and paraglossae 

 tend to disappear, although I am not certain that neither 

 paraglossse nor glossas are well developed in the Diptera, since 

 Peterson, 1916, who has examined a wide range of Diptera, 

 thinks that glossae and well developed paraglossae are to be 

 found in this group. On the other hand, if one examines a 

 specimen of Bittaciis and Panorpa, it is quite evident that the 

 maxillse (excepting the palpi) are reduced, or have begun to 

 unite with the labium, and that the glossas and paraglossse 

 of the labium have almost disappeared, while the labial palpi 

 have become approximated in the median line, thus assuming 

 a condition suspiciously like that exhibited by the Dipteron 

 shown in Fig. 6. A study of the embryological development 



