ZooL.— Vol. III.] KELLOGG— NET-WINGED MIDGES. 203 



IV. Notes on the Structure of Larv^ and 

 Imagines. 



The published notes on the structure of the Blepha- 

 roceridae, in addition to the external details more or less 

 superficially described in the specific descriptions of various 

 authors, are included in the papers of Dewitz (1880), Miiller 

 (1881), and the writer (1898, 1899, 1900). 



The suckers of the larvae are described in more or less 

 detail by all of these writers (in each case for a different 

 species). For the sake of making this paper as nearly as 

 may be, in brief compass, an introduction to the study of 

 the North American Blepharocerid^, there is here quoted 

 part of the already published description, with the figures, 

 of the suckers of the larvae of Blepharocera cafitata (Kellogg, 

 1900). 



The body of the larva consists of six parts, separated by 

 distinct constrictions. By making sagittal longitudinal 

 sections through the body it can be seen that the anterior, 

 apparently single, segment is composed of the fused head 

 and three thoracic segments, while the most posterior part 

 is composed of the last two abdominal segments, the inter- 

 vening parts representing each a single abdominal segment. 

 That the anterior body part comprises the head and thoracic 

 segments is also proved by the fact that the imaginal discs 

 of the legs and wings are to be found here. The larva is 

 footless; but each body part (not body segment) bears a 

 pair of small, unsegmented, pointed projections (PI. XXI, 

 fig. 6, I. p.), situated on the ventral aspect of the lateral 

 margins. This projection may be of slight use to the larva 

 in locomotion, but, at best, only of slight use. The real 

 organs of locomotion and of attachment to the rock bed of 

 the stream are the six "suckers," one of which lies on the 

 median ventral aspect of each body part. There is but one 

 sucker for the combined head and thorax, and but one for 

 the last two abdominal segments. By means of these 

 suckers the larva clings to the rock bed of the stream, 

 despite the impact of the swiftly flowing water. The larva 



( 2 ) January 28, 1903. 



