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 modifled, the heel being less prominent, and the 

 instep disappearing, i. e. shaped like a flattened C3'linder, 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 

 projecting.^ 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 

 impal 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 brauches, which 

 again subdivide into twigs. The number of twigs is constant 

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

 to upward of 60 in one of our own. For a description of their 

 structure see a paper by Dr Volger, Die Tracheen Kienioi der 

 H i mil 1 ien Puppen. 



On the segTuents are a number of email, regularly arranged 

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

 case. The arrangement of these hooks ajtpears to be uniform 

 for a given s[)ecie.«. The pui)al stage lasts about a week, some- 

 times a little longer. The adult luakes its escape froui the 

 pupal skin through a longitudinal rent on the dorsum of the 



iSee Riley's fif,'nre of pupal case in U. S. Dep't Agrie. An. Rep't 1886, of 

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

 p.53. 



