98 ENTOMOLOGICAL SOCIETY 



THE LOG-CABIN BUILDER. 



(Limnepkilus indivisus Walker.) 



By C. B. SIMPSON. 



During the spring of 1900, while at Ithaca, N. Y., the writer 

 incidentally made some observations upon the larvae of this cad 

 dis fly. The larvae were found in abundance in a series of still 

 ponds near Fall Creek during April and part of May. They 

 were found as early as April 9 in 1900 and March 31 in 1901. 

 At these times the larvae were from one-fourth to half grown. 

 In March, 1901, the winter ice was out, but a thin sheet of ice 

 was present. The upper ponds of the series contain water 

 throughout the season, while the lower ponds are dry about mid 

 summer. 



About April 20 the larvae were nearly all full grown. By plac 

 ing the cases containing larvae in a dry box it was found that the 

 larvae would leave the cases and thus obviate injury or killing the 

 larvae in removing them forcibly. 



When full grown the larvae are about three-fourths of an inch 

 in length. The head, prothoracic and mesothoracic shields and 

 legs are dark brown or black in color, while the remaining parts 

 are clouded white. The legs are well developed and bear well 

 developed claws. The first abdominal segment bears one dorsal 

 and two lateral tubercles. There are four principal rows of fila 

 ments which are nearly white by reason of the trachae and air 

 contained in them. On each lateral margin of the abdomen 

 there is a row of fine stiff hairs placed closely together. The 

 caudal segment of the abdomen bears two prolegs which are 

 armed with strong hooks. The use of these structures is evident 

 upon examining the habits of the insect. The tubercles and the 

 prolegs are used to hold to the inside of the case. The filaments 

 are respiratory, and the rows of fine hairs are for inducing cur 

 rents of water. 



The cases of the younger larvae consist of small sticks, grass 

 stems, leaves and moss arranged in a more or less irregular 

 manner. The material of which the cases of the older larvae are 

 built depend in a great measure upon the material in hand : 

 when an abundance of leaves is present in the bottom of the 

 pond these are for the most part used, and, in many, leaves alone 

 constitute the case. These bits of leaves are placed one upon 

 the other at right angles to the axis of the case, and silk is used 

 to fasten them in place. These are placed around the entrance 

 to the case in an irregular manner, and are always eaten so as to 

 make a smooth interior although the exterior is irregular. When 

 larvae are placed in an aquarium they feed from each other's 

 cases and break off pieces and incorporate them in their own 



