INTRODUCTION. 
A few caddis-worms that construct portable cases use no other 
material than silk in their structure. By far the greatest number 
of species, however, use stones or sticks cemented around a more 
or less heavy lining of silk. The cases, regardless of their external 
form, are circular in cross-section. Some are of uniform diameter, 
throughout their length, while others taper, cornucopia-like, from 
a broad mouth to a very narrow caudal end. In building their 
cases the larvee add new material to the cephalic end. Some species 
build rapidly and cut about as much from the caudal ends of their 
dwellings as they add to the front ends. These species make tubes 
of uniform diameter throughout their length. Other species add 
to the front ends of their cases as the larve grow in length and 
breadth, but never remove material from the caudal ends. The 
result of this form of construction is a case that is of minute size, 
but large enough to accommodate a newly hatched larva, at its 
caudal end, and gradually increases in breadth as the larva grows, 
thus forming a cornucopia-shaped tube. Figures of both types of 
cases will be found on following pages. 
Toward the close of the larval period there is a change in the 
habits of the caddis-worms. They stop eating entirely and fre- 
quently hunt some protected spot, such as crevices in bark or roots, 
or they burrow into wood or soil. Often the form and material 
of their cases is greatly altered, and there is almost always a mesh 
or grating spun across the two ends of the case to protect the help- 
less pupa against active enemies and the greater peril of silt. After 
the mesh is spun the larva becomes sluggish and entirely incapable 
of walking. This stage in the larva’s life is called the prepupal 
period. It usually lasts but two or three weeks, but in the genus 
Neophylax it extends over the greater part of the summer. 
During the active larval period, when the caddis-worms are free 
to move about and feed voraciously, they lay up a reserve supply of 
food to carry them through the transformation period and through 
their adult lives, when they feed little if at all. They then pass 
through a quiescent or pupal stage. During this period a great 
change takes place in the structure of the insect. From the worm- 
like larva, fitted for aquatic life and provided with greatly de- 
veloped mouth parts and alimentary tract, comes forth a moth- 
like, winged insect that is air-breathing and has vestigial mouth 
parts and feeble alimentary tract, and seems to have no other object 
than to mate and oviposit. So great is the change that no one 
4 
