1900] ENTOMOLOGICAL NEWS. 309 



while the most posterior part is composed of the 

 last two abdominal segments, the intervening parts repre- 

 senting each a single abdominal segment. That the anterior 

 body parts comprises the head and thoracic segments is also 

 proved by the fact that all 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, unseg- 

 mented, pointed projections (Fig. 1, 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 (Fig. 1, s). 

 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 

 can loosen its hold with the suckers voluntarily ; and, by 

 loosening those at one end of the body, swinging this end lat- 

 erally and refastening it, and then loosening the other end 

 of the body and swinging and refastening it, a slow but safe 

 locomotion, chiefly lateral, is possible. The larvse move about 

 not a little, especially from the necessity of continually moving 

 from the edge out farther into the stream as the water of the 

 little stream gradually lessens in quantity. 



The structure of these suckers and the manner of their 

 working are of interest. The ventral (external) aspect of a 

 sucker (Fig. 1, s.) shows a central opening, surrounded by a 

 strong, flexible, concave rim, marked with alternating concen- 

 tric bands of thicker and darker and thinner and lighter bands 

 of chitin. The rim projects considerably ventrad, so that a 

 considerable free or air space is enclosed by the rim when its 

 outer edge is applied to any surface. In dorso- ventrad sections 

 transversal to the body of the larva (see Fig. 1, &.) the whole 

 structure of the sucker is apparent. The cup- shaped sucker 

 is seen, after all, not to consist of a rim around a circular open- 

 ing, but to be simply a part of the outer body wall (true skin 

 and chitin cuticula) peculiarly folded and modified to act as a 

 sucker. The projecting cup-like part (Fig. 1, r.) of the sucker 



