266 W. WESCHE. 



insect shows that the pubescence of the legs approximated closely 

 in Gynoplistia bella, particularly in the region of the tarsi; in 

 Ptychoptera albimana, P. lacustris, P. scutellaris, and Rhyphus 

 fenestralis the structure of the tibial bristles is practically iden- 

 tical. This is certainly remarkable, as Woodworth on the evi- 

 dence of the venation 1 has suggested that this family is more 

 closely related to the diptera than any other, branching off after 

 the Neoptera had left the Metabola. 



I think that we may assume that the primitive type of pubes- 

 cence on the legs of diptera was somewhat similar to that which 

 yet exists in Rhyphus and the Tipulidae; and that when marked 

 bristle structure or armature is found the insects are specialized. 

 So we recognize, and this harmonizes well with other characters, 

 that the Bibioninae and the Culicinae are the most specialized 

 subfamilies among the Nemocera, such forms as Dilophus, or 

 Mucidus and Sabelhes making this clear. In the Myceto- 

 philidae, Sciara preserves the older type, while Mycetophila in 

 the strong spines on the tibiae and tarsi is more specialized, which 

 idea is quite confirmed by the ocelli, three in Sciara, two in 

 Mycetophila, and these remote from their usual position. The 

 other families (I am not certain of the Blepharoceridse) are all 

 of the simpler types as is the genus Scatopse and the subfamily 

 Corethrinae. 



Among the Brachycera, in the families with many genera, a 

 number of variations between simplicity and complexity will 

 be found, mostly as secondary sexual characters in the male, 

 while the predaceous insects will be found modified in both sexes. 

 The more striking examples of the latter will be found among the 

 Empidae, the Asilidae appearing to confine their armature mostly 

 to the tarsi. The Phoridae have a peculiar and characteristic 

 chaetotaxy, but do not vary markedly; while the Leptidae, 

 Stratiomyidae, Tabanidae and Cyrtidae are all of the simpler type, 

 the Leptidae most nearly like the Tipulidae, retaining the peculiar 

 bristle structure. The Platypezidae and Pipunculidae show 

 various modifications of rows of long bristles or hairs as well as 

 peculiarly modified bristles. In some Platypezidae these bristles 



1 "Wingveins of Insects." Univ. California Publications, Entomology, Vol. i, 

 p. 145, 1906. 



