AQUATIC MIDGES AND SOME RELATED INSECTS. 35 



That the larvae prefer bacteria to the more solid tissues can be observed by their 

 behavior in a petri dish, where they move about in a very characteristic manner. The 

 head is carried at an angle of about 45 to the bottom, and the anterior prolegs are the 

 chief organs of locomotion. They alternate with the head in supporting the body and 

 are provided with about three rows of strong coarse spines. The larva moves along by 

 a rapid alternate depression of the head and backward stroke of the anterior prolegs. 

 The posterior prolegs are little used, and the larva curves its body up first on one side 

 and then on the other, thus aiding the head and anterior prolegs in their forward move- 

 ment. The larvae always move forward, and the spines on the inner border of the max- 

 illae and hypopharynx are doubtless of prime importance in collecting the fine organisms, 

 in correlation with this progressive method of feeding. 



The pitcher plant seems to be the chief natural environment where such food sub- 

 stances are available. While its inner surface is covered with closely placed spines which 

 all point inward, it nevertheless offers a favorable environment to such small larvae, 

 for they are able to move about among these spines and collect the bacteria and mold 

 spores which accumulate there. That these larvae may find conditions at least imper- 

 fectly suited to their method of feeding in other environments would seem to simplify 

 the explanation of their distribution. The swamps are widely separated, and the 

 pitcher plants are not numerous, and if a few larvae could live in other environments the 

 distribution would be more readily accounted for. 



Group VI : Subgroup B. — Orthocladius sp. (?) 



These larvae have not been bred, but are abundant and will doubtless be found to be 

 one of the common species. They are found in flowing streams about Ithaca and were 

 collected the first part of June among the debris resulting from the disintegration of 

 Cladophora. They were at that time very numerous, but the writer has been unable 

 to find them on several occasions during the last of July and the first part of August. 

 As forms found in flowing water are hard to rear, none of those taken early in the season 

 were reared. 



LARVAL CHARACTERS. 



• 



The larvae are bluish green in color and have several rows of coarse black claws both 

 on the anterior and posterior prolegs. The caudal filaments are placed on very small 

 short papillae, and the filaments themselves are very short, scarcely extending beyond 

 the anal gills. The head parts are rather stout (figs. 29 and 30), and the fan-shape mem- 

 branes are entirely absent. 



The larvae apparently do not make use of their well-developed silk glands for the 

 purpose of building tubes. It seems probable that they would not be so well developed 

 unless they had some important function. The author has concluded therefore that 

 their development is correlated with the nature of the food eaten. 



FEEDING HABITS. 



The larvae creep about on the surface of submerged stones and even out of the water 

 where the rocks are only moist. A very noticeable feature in the behavior of these 

 larvae is the frequency with which they turn over. This habit of rolling over every few 



