225 



insects enter the water to oviposit has not been observed. The larvae 

 are sometimes found in very large numbers in deep water in the 

 Illinois River. When full-grown they average 15 mm. in length, 

 and at the thickest part do not exceed i mm. in diameter, being very 

 slender and slightly attenuated towards either extremity. The head 

 is subconical and slightly more than half as long as the first thoracic 

 segment. The antenUcT are almost indistinguishable, the upper part 

 of the mouth hangs over the front, forming a sort of flaplike covering 

 to the orifice, and as the mouth parts are easily retracted the whole 

 aperture may be tightly closed. The maxillary palpi are normally 

 extended and distinct; the mandibles are long and very slender, 

 generally very much retracted within the orifice. There are two 

 confluent black pigmented eye-spots on each side of the head. The 

 first three (thoracic) segments are slightly shorter than those of the 

 abdomen, the latter being but little lengthened as they recede from 

 the base, while the twelfth is very slender and slightly the longest. 

 There are no distinct respiratory organs, or blood gills on the anal 

 segment, the only appendages consisting of two pairs of hairs on either 

 side near to the apex. In transforming to the pupa the larval skin 

 is ruptured dorsally almost the entire length of the first two thoracic 

 segments and the skin is cast entire. The pupae are found floating 

 at the surface of the water, and being capable of a slight movement 

 are able to make their way either to the shore or to some unsubmerged 

 object upon which they may crawl to undergo their last transforma- 

 tion. The pupa appears strikingly different from the entirely smooth 

 larva, being distinctly warty abdominally, the function of the 

 protuberances being evidently that of assisting in the progress of 

 the pupa over the surface it may choose for its transformation. It 

 appears from notes made by Mr, C. A. Hart, that it is essential to 

 the emergence of the imago that the dorsal surface of the thorax of 

 the pupa be exposed to the air, evidently to facilitate the rupturing 

 of the skin, and when the pupa finally manages to crawl from the 

 water it lies with the dorsal surface uppermost and the thoracic end 

 slightly raised from the sand. The imago emerges very soon after 

 the pupa reaches a suitable surface for transformation. 



The pupae of Ccratopogonince are readily separated from those 

 of other Chironoinidce by the fact that the wing cases are closely 

 adherent to the surface of the body, whereas in the other group they 

 are always distinctly separated from the body and somewhat flaplike. 



The details here given arc equally applicable to Palponiyia 

 sclncarzi, JaluuinscnicUa albaria, and /. tlaz'idula. 



