238 

 BELVOSIA— A STUDY. 



By S. W. WiLLiST<jN, M. D., Lawrence, Kans. 



In Brauer and Bergenstamm's recent work on the " Muscaria scliizo- 

 metopa" there is given a list of over four hundred genera of TachiuicLne 

 accepted by the authors, one hundred and eighty of which have been 

 recently proposed by themselves. To these must be added forty-three 

 proposed by Townsend within the past two years, making altogether 

 about four hundred and fifty current genera in this one family. 



It may be interesting to note that the entire number of species stud- 

 ied by Brauer and Bergenstamni is given at fifteen hundred. Presuma- 

 bly a large proportion of these were from Europe, Avhere the family has 

 been most studied, especially by Desvoidy, Kondani, Schiner, and Ko- 

 warz. In the United States there are, I am confident, at least six 

 hundred species in collections at the present time, and probably more 

 than twice as many in reality.* At present the North American species 

 are distributed among about one hundred and thirty genera, about one- 

 half of which are unknown to occur outside of these limits — a remark- 

 ably high proportion. 



' It will be a long time before the family is as well known as are many 

 ♦other families of American Diptera, and the reasons therefor are not 

 hard to find. Species, geuera, and even families show such slight plas- 

 tic or coloratioiial differences that only the most patient study will de- 

 fine their limits. At the present time there is a decided tendency to 

 base the classification of even the higher groups upon apparently triv- 

 ial characters. Most naturalists have' long since abandoned the idea 

 that genera, or even families, represent anything but the conveniences 

 of classification, and the recent writers on this family are probably right 

 in seizing upon any characters that will satisfactorily group the vast 

 number of species irrespective of their relative values. But it is very 

 probable that, in the proposal of so many genera in such rapid succes- 

 sion, many characters have been employed which future research will 

 show to be entirely inadequate. We yet know very little about indi- 

 vidual variations in this family, or the real value of many of the char- 

 acters now used. The absence or presence of a bristle may be found to 

 represent a group of species, but we should first learn how constant the 

 character is in species. 



What I would here ofier are the results of a study of considerable 

 material, which has until recently been considered to belong to a single , 

 species, but which is now thought to appertain to distinct genera. I 

 have selected and figured, almost at haphazard, nine specimens, every 

 one of which presents so-called specific or generic characters. I could 



" My own collection of South American Tachinidse includes over foiir hundred 

 species. 



