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 [p1.35, 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. pictipes, 
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 
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 60 in one of our own. For a description of their 
structure see a paper by Dr Volger, Die Tracheen Kiemen der 
Simulien Puppen. 
On the segments are a number of small, regularly arranged 
black hooks, by which the pupa is attaehed 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 
ree 
1 See Riley’s figure of pupal case in U. S. Dep’t Agric. An. Rep’t 1886, of 
S. m eridionale, or U. S. Dep’t Agric. Div. Ent. Bul. 5, n. s. 1896. 
p.53. 
