350 NEW YORK STATE MUSEUM 



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

 pulled out of its case. Spinning is rarely seen excepting when 

 the insect is in a stream of running water." 



The pupal cases are usually composed of a rough, tough, 

 clothlike fabric, and vary in shape with the different species. 

 Three types of cases are known to me. One is shaped like a 

 shoe, entirely concealing the pupa [pl.35, fig.5]. This is some- 

 times slightly modified, the heel being less prominent, and the 

 instep disappearing, i. e. shaped like a flattened cylinder, the 

 planes of the bases being parallel, but oblique (S, p i c t i p e s , 

 and in a California species). Another, the most common type, 

 is like that of a wall pocket, the head and the thoracic filaments 

 I)rojecting.i The third type is structureless, composed of a 

 matted mass of thread on the rock, sometimes only partly 

 covering the pupa; as in S. hirtipes. Large numbers of 

 pupal cases are frequently found matted together, carpetlike; 

 The pupa are generally of a pale or golden brown color, the 

 abdomen being somewhat darker. The eyes of the adult soon 

 become visible, as also the legs and wing cases. Eight body 

 segments are visible from the dorsal surface, not counting the 

 anal. The respiratory filaments arise from a single stalk on 

 each side; this stalk has a variable number of branches, which 

 again subdivide into twigs. The number of twigs is constant 

 for a given species, ranging from four (in a European species) 

 to upward of GO in one of our own. For a description of their 

 structure see a paper by Dr Volger, Die TracJieen Kiemeii der 

 ^imnlieii Puppen. 



On the segments are a number of small, regularly arranged 

 black hooks, by which the pupa is attached to the fibers of its 

 case. The arrangement of these hooks appears to be uniform 

 for a given species. The pupal stage lasts about a week, some- 

 times a little longer. The adult makes its escape from the 

 pupal skin through a longitudinal rent on the dorsum of the 



iSee Riley's figure of pupal case in U. S. Dep't Agric. An. Rep't 1886. of 

 S. m e r i d i n a 1 e , or U. S. Dep't Agric. Div. Eut. Bui. 5, a. s. 1896. 

 p.53. 



