Dialysis and Triptotricha. 



BY S. W. WILLISTON. 



In the Insecta Saundersiana, p. 4, Walker described a genus of 

 diptera under the name of Dialysis, referring it to the Xylophagidae. 

 He based the genus upon a specimen which he had previously referred 

 AowhXiwWy to Xylophagus aviericanus Wied.* From the description, 

 Loew was in doubtf as to the location in the Xylophagidse. In 1879, 

 Bigot recognized the genus and described a species (Z>. dispar) of 

 it from California. J Later Osten Sacken examined Walker's type 

 specimen and referred it to the genus Triptotricha,% but did not accept 

 Walker's name, contending that the genus had never been recogniz- 

 ably described. Rather reluctantly I accepted this rejection of the 

 name in my Synopsis of the genera of LeptidK,|| though the syno- 

 nymy was recognized. 



In 1889 Bergroth described** a new species of the genus from the 

 United States, under the name Dialysis disparilis, led thereto by his 

 well-known views regarding the rigidity of zoological nomenclature. 

 He urged that Bigot had been able to recognize the genus, though he 

 had erred in locating it among the Xylophagidae. 



Until recently all the species known to me have two spurs on the 

 front tibiae, and I have so defined Triptotricha in the generic synopses 

 given by me, overlooking the fact, to which my attention has recently 

 been called by Prof. Aldrich, that the genus Triptotricha Loew was 

 said by its author to have one tibial spurff ("Die von mir erichtete 

 Gattung Triptotricha gehort, wegen der Anwesenheit eines starken 

 Sporns an den Vorderschienen," etc.). In his original diagnosis of 

 the genus;};! he makes no mention of this character, and it so happens 

 that the type species of the genus has two anterior tibial spurs, as 

 has been shown by Townsend.§§ This last mentioned author also 

 shows that one of the species placed by Loew in the genus {T. rufi- 

 thorax Say) has but the one spur. 



*List, etc., I, lr.'8. 



tMenog., I, 16. 



tAn. Soc. Ent. Fr. 1879. 



§Berl. Ent. Zsit., XXVII. 295. 



llEntom. Amer., April, 1885. 



*-Wien. Ent. Zeit., p. 296. 



t+Berl. Ent. Zeit., XVIII, 380, 1874 



iJCentur., X, 15. 



^§Proc. WasU. Eut. Sou., II, 118. 



(.263) KAN. UNIV. QDAR., VOJ.,. UJ. NO 4, APKl|j, 1, }895, 



