174 NI:W YOKK STATI: :\irsi;iM 



KEY TO SPECIES OF DIAMESA 



Larvae 



<i Mimtli parts as shown on pl.2o, figr.9 1. \v a 1 t 1 i i 



(/ Mouth parts as shown on pl.:;;. li-s. is to 17, ; the dorsal surface of the 

 ahdoniinal segments marked with transverse I'aseine (European 



-peries I .",. < U 1 i < o i d e S 



Pupae 



a Anal end with six slender filaments 1. w a 1 I 1 i i 



an Anal end with ek'lit lilanieiits :5. e u 1 i e o ides 



Imagines 



it I la'teres pale yellow ; t horaeii- -t ri| >es Mark ; len^t h 1.5 to 5 mill. (United 



Stales. Knro|te. ( Jivenlaiid i 1. w a 1 t 1 i i 



ad llaltores white ; thoracic stripes cinereous black ; length JJ.". to i/jr> mm. 

 i < iivenlaiid i I', chorea 



I cannot separate a b e r r a t :i Lundheck (1898) from 

 w a 1 t 1 i i . 



1. Diamesa waltlii .Mei^en 



1838 Diamesa Meigen. Syst. Besehr. 7:13,1 



1856 Chironoinus Ilalid. in Walk. Ins. lirit. Dipt. 3:194 



1864 Diamesa Schiner. Fauna Austr. L':r,1.~> 



1S9S Diamesa a her rat a I.undbeek. Videiisk. .Meddel. L's'.i, 77 



Larva, i 1'l.L'O. Jig.!h Tlir larvae \\<-rc taken in company with 

 the larvae of T h a 1 a s s o in y i a f u s c a amoiio llie alpie ou 

 the surface of rocks over \vhirh llie water ilows i-apidly. In color 

 it is pale liTeen. in .u' ( 'ii'i'al appearam-e and even in many/- details 

 of structure it Breath i-esemliles T li a 1 a s s o m y i a fusca. 

 The dorsal selerile of llie head is elon.ua led. shield-shape, with 

 two pairs of marginal setae; on the lateral selerite there is one 

 seta near the base of the mandible just above the lateral line, 

 one pair belo\v this one and a little cephalad; another pair about 

 one quarter of the len^ih of the head caudad of these but lying 

 as far below the lateral line as the first is above. Directly caudad 

 of the first, but midway between the front and hind margin of the 

 head, is another; close to the dorsal suture, one quarter the length 

 of the head cephalad of the caudal margin is still another; and 

 finally there is a single one on each side at the base of the labium. 



The mouth parts are as shown in the figure. The epi pharynx 

 is shown with its parts extended. In the figure given by the 

 writer in Unl. GS. X. Y. State Museum (1903) these parts are 

 shown folded down. The lateral arms (la) are each expanded 

 apically into a handlike process with T or S fingers. The mandi- 

 bles each have 5 blunt teeth, a fringe of coarse-branched hairs 

 projecting mesad. and two stout setae on the dorsal surface near 



