132 



frontal tuft often multiple, or with four or five hairs, upper generally with four 

 hairs; between them two single feeble hairs. Eyes large. 



Thorax rounded, much wider than long. Hair formula of frontal border 

 221123321122. All hairs especially 33 very long, reaching beyond the brushes when 

 extended; lateral hairs single and in tufts. 



Anterior abdominal segments very short, posterior ones elongated. Lateral tufts 

 of first two segments with four to five hairs; two or three hairs on third to sixth 

 segment. Subdorsal hairs on third to seventh segment in tufts of four to five, often 

 in stellate arrangement with angles of 90. Eighth segment with hairs in ordinary 

 arrangement. Air-tube extremely long, six or seven times longer than broad; pecten 

 short, restricted to basal fifth, consisting of about ten teeth; single tooth short, not so 

 broad as in pipiens and only furnished with two, rarely three, branches. Hair-tuft of air 

 tube double or triple. Between hair-tuft and apex four tufts double, often two out 

 of line. Lateral comb of eighth segment consisting of numerous scales in a triangu- 

 lar patch ; single scale extremely long more than four times longer than broad with 

 feathered tip; restricted after the spatulated part. Anal segment much longer than 

 broad, ringed by a plate. Dorsal hair-tuft with a few short and two very long brist- 

 les; ventral brush well developed, confined to the barred area without free tufts 

 before. It consists of about 10 12 rays, every ray carrying from five to seven hairs. 



Gills extremely long, narrow, acute often twice as long as anal segment. 



Mouth brushes very large, distinctly divided into two parts, the inner part without 

 comb-bristles; palatum coated with rather short hairs. Mandibles quadrangular, 

 three spines before the collar; a row of long cilia from a collar; outer margin with 

 about ten scales; bearing short hair-tufts; dentition: from three to four teeth on a 

 process, the first of them very long; a long serrated tooth before; process below 

 undivided with a few hairs; angle below sharp, a group of hairs within and a row 

 at base. Maxilla conical, divided by a suture. At the apex a tuft of very long, fea- 

 thered hairs. Along the suture a series of shortening hairs. Inner half between su- 

 ture and inner margin with sharply defined series of long bristles; the outer half 

 with a spot, covered with soft hairs and a short spine near apex. Palpe moderate, 

 terminal digits long. Mental plate extremely high, straight sides and triangular apex 

 with a large central tooth and from nine to eleven teeth on each side; the first 

 three small and densely crowded. - - Colour milky white. 



As will be seen from the description of the larva of C. pipiens and C. nigri- 

 tulus there are great and conspicuous differences! 



The larva of C. nigritulus is always about two millim. smaller than that of 

 C. pipiens; the number of subdorsal hairs in C. nigritulus is from four to five, in 

 that of pipiens only two ; the scales in the comb are much longer in C. nigritulus 

 than in C. pipiens and the sipho is about one third longer than that of this species ; 

 further the teeth in the pecten are narrower. Also the arrangement of the frontal 

 tufts differ a little in the arrangement. 



