Sept., 1904.1 Knab : Appendages of Mosquito Larv.^. 175 



THE EPISTOMAL APPENDAGES OF MOSQUITO 



LARViE. 



By Frederick Knab, 



Ureana, III. 



(Plate X.) 



In sorting mixed captures of mosquito larvae some trouble was ex- 

 perienced, partly on account of the close resemblance of some of the 

 species, but more particularly on account of the considerable varia- 

 tion, not only in color, but also in such characters as the length and 

 form of the antennce, the breathing-tube, gills, etc. To add to the 

 difficulty, there is more or less of a change with each moult. 



The head of the larva bears upon its dorsal surface a number of 

 conspicuous hairs or tufts of hairs. Upon comparison of the differ- 

 ent species and their stages, it was found that these hairs existed in 

 all of them. They differed not only in each species examined but 

 also in each of the stages. Three pairs of these hairs or hair tufts are 

 conspicuous appendages of the head and readily available as specific 

 characters. They may consist of single hairs, of two or three hairs 

 with a common base, or of fan-shaped tufts of hairs — each species pre- 

 senting specific distinctions in the number of hairs in the tufts, as also 

 in their length, coarseness and the relative position. Their bases are 

 inserted into sockets so that they sway about with the motions of the 

 larva. Doubtless they are sensory in function and help to keep the 

 larva in touch with its surroundings. These appendages are all situ- 

 ated upon the epistoma — using that term in the sense of Schioedte 

 and other European writers for the part included within the epicranial 

 sutures. The appendages are arranged upon the area between the 

 antennae and usually somewhat farther back. However their relative 

 position differs considerably, not only in different species, but also in 

 the different stages. The accompanying diagrams will show these 

 differences in a few forms. In the mature larva of Culex restuans 

 the six appendages are in a transverse series, nearly in a line. The 

 innermost pair of these appendages I have called the median pair ; the 

 two on the outer sides of these the intermediate pair ; the third pair, 

 close to the margin and near the base of antennse, the outer pair. 



In many species the median pair is inserted farther back and 

 sometimes come almost longitudinally into line with the intermediate 



