166 C. R. Osten Sacken: 



paper, the head of which is represented in his Tab. VIT, fig. 14. 

 Dr. Willis ton apparently had no copy of Dr. F. M.'s at hand, 

 otherwise he would probably have coine to the same conclusion. 

 Williston's wording: „proboscis directed downwards, a little longer 

 than the vertical diameter of the head, palpi slender, about as long 

 as the proboscis, apparently composed of four joints," and especially 

 the words: „ungues large, simple," as well as other data, agree with 

 the above mentioned feniale. Dr. F. M. describes two females: a 

 bloodsucking one, provided with mandibles, with large eyes and long 

 claws (fig. 14 head, fig. 9 tip of leg); and a flowersucking one, with 

 small eyes, short claws and no mandibles (fig. 13 head, fig. 8 tip of 

 leg). Dr. Williston's description says nothing about the mandibles, 

 nor about the comparative size of the eyes, but the words „ungues 

 large, simple" are decidedly in favour of the bloodsucking female. 



The specific identity of Dr. F. M.'s bloodsucking female with 

 Williston's Snowia rufescens is rendered probable by the vicinity 

 of the locality (S. Catherine and Rio). If my supposition be correct, 

 S. rufescens would be the first species described in the mature State 

 among the group of larvae studied by Dr. F. M. The question of 

 the other forms must remain open, until we likewise obtain mature 

 specimens of them. 



The holoptic male (fig. 7 and 15, head) was taken by Dr. M. 

 for the male of the dimorphic females. He says (p. 81): „The eyes 

 of the males, as in many other Diptera, occupy nearly the whole sur- 

 face of the head, being more or less contiguous up to the Vertex." 

 But he was not aware that, in this respect, the Liponeuridae form 

 an exception among Diptera. As far as our experience goes, the 

 eyes of the two sexes in this family have nearly the same structure, 

 they are, in both sexes, either holoptic, or dichoptic, either bisected 

 or not. Therefore, according to our present notions, the holoptic 

 male fig. 7 and 15, cannot belong to dichoptic the female fig. 14. I 

 have expressed the same opinion in my notice in the Ent. M. M. 

 XVII, p. 130. At that time I formed my opinion upon Dr. F. M. 

 article in „Kosmos" only. Now, that I can compare the principal 

 work, my doubts have even gained strength, because I perceive that 

 the eyes of the male are not only contiguous, but at the same time 

 bisected. The eyes of the females, in the figures, are neither con- 

 tiguous nor bisected, and in this they agree with the statemcnt of 

 Willis ton about Snoivia: „eye-facets uniform" (p. 1-20, line 7 from 

 top). The mexican Paltostoma which I saw in Turin (0. S. 1878, 

 p. 411) also has uniform eye-facets. The letterpress of Dr. F. M. 

 p. 81, on the contrary, says distinctly of the eyes of the male: „the 



