336 KANSAS UNIVERSITY SCIENCE BULLETIN. 



S. pictipes is described as follows: "In spinning, the thread 

 issues from the mouth and is placed in the different positions 

 by the thoracic proleg. The head is bent down, and with the 

 proleg- the thread is drawn around the body, except the head. 

 The skin of the head is then cast off, and the insect then pulls 

 itself out of the .skin of the body, leaving it whole. The cast 

 skin may often be found in the cocoon with the pupae. The 

 cocoons are commenced at the upper margin and spun con- 

 tinuously down to the caudal end, where several threads are 

 drawn from the cocoon and attached to the last one or two 

 of the body segments of the pupse. The threads hold the pupa 

 very firmly and are always found when the pupa is pulled out 

 of its case." 



I found it very difficult to watch vittatum spin their cocoons, 

 because the adult larvaj almost invariably go to the under side 

 of the rocks and debris or seek a protected place in the ripples 

 for pupating. Vittatum pupae are, when first formed, drawn 

 back into their cases so that only the pupal gills show from a 

 dorsal view. Inside of a day or two they begin to push out a 

 little, showing the head bent down and the origin of the gills. 

 On the fifth day after pupating I observed some pupse that had 

 swung free from their cases and faced in the opposite direc- 

 tion alongside of them. 



They were still attached by two threads that ran into the 

 pupse cases. A description of the same habit of slipping from 

 their cases is given in the United States Department of Agri- 

 culture Year Book, 1886, p. 508. We observed a pupa in a 

 vessel of water turn over in its case. It was seen to do thi;; 

 several times, always turning on its ventral side. 



When the pupa is drawn from its case, upon close examina- 

 tion one can see two small black blunt hooks on the dorso- 

 caudal end of the pupa, and eight similar hooks on the dorsal 

 front marginal side of the abdominal segments, four in a row 

 on each side, parallel to the margin of the segments ; they are 

 a part of a membranous covering as shown in plate XXXIX, 

 figure 9. By means of them it attaches itself to the silky 

 threads of the pupa case. 



A general external view of the individual pupa on a rock is 

 shown in plate XXXIX, figure 7. One can see the origin of 

 the pupal gills, and the head tucked beneath, also the prom- 



3. N. Y. St. Mus. Bui. 68. 



