XXxii/21] KNTOMOLOr.JCAL NF.\VS 231 



long as the others combined including the large basal segment, 

 or twice the length of segments 2 to 7 combined; dorsal keel 

 not produced as far as the tip of the inner process of the basal 

 segment of the clasper ; eyes densely short haired, all claws of 

 the male somewhat broadened at the tip. flat and brush like ; 

 fore basitarsus nearly 0.7 as long as the corresponding tibia. 



walttii. 



Mr. Muttkowski (p. 118, 1915) calls attention to the notice 

 able difference in the form of the larval lahitim of D. mcndotac 

 and D. ivaltlii and ventures the opinion that I may have con- 

 fused my material of D. i^alllii and Cardiocladius (Tlialas- 

 somyia] obscura when writing my papers (1903, 1905). 



There is however no error in my rearing records of these 

 species. In the first place, the arrangement of the teeth in the 

 labium is subject to considerable variation within a genus as 

 may be seen in Chironomus, and there seems to be no reason 

 why this should not also be so in Diamcsa. Secondly, I find 

 in my notes the following: "Six reared specimens of Dianicsc. 

 and their six cast larval and pupal skins. Reared Nov. 24. 

 Material collected from swift water, Cascadilla Creek, Nov. 

 14." The figures in my 1905 paper were based in part on this 

 material. The figures in 1903 paper were made from speci- 

 mens taken at an earlier date. 



In the third place, the larva of Tlialassoniyia obscura is not 

 full grown until spring, the adults appearing from May to Sep- 

 tember, while the larva of Diamcsa waltlii in this locality is full 

 grown only in the fall and winter, the adults appearing from 

 November to April. Specimens collected in late fall and early 

 winter therefore cannot be confused. 



Concerning the early stages of D. fnlra all that can be said 

 is that the larvae must live in flowing water, since the adults 

 were captured under a tent trap placed over a riffle. The 

 larvae of the other two species found in this country and that 

 of T. (Cardiocladius} obscura may be distinguished as follows: 



1. Middle tooth of labium at least as wide as three lateral teeth, 1>r<>:id1\ 



truncate and with convex margin T. obscura 



2. Middle tooth of labium broad. iu.-iri.Mii concave />. men: 



3. Middle tooth of labium narrow, not twice as wide as tin- first 



tooth. . . /'. U ;.'//(; 



