92 
INTRODUCTION TO 
presents tlie appearance delineated in the adjoining 
Wood-cut. 
The pupa having made so much nearer an ap- 
proach to the perfect form than the larva, exhibits 
some indication of the principal divisions of the body 
which afterwards become so strongly marked. A 
slight constriction frequently points out the bound- 
aries of the head, thorax, and abdomen. Regarding 
the exterior sheath as the case {theca) of the pupa, 
Kirby and Spence have assigned a nomenclature to 
its principal parts : the anterior division enclosing the 
head, is called the Head-case ( cepkalo-theca ) ; next 
to this is the Trunk -case {cyto-theca) ; and lastly the 
Abdomen-case ( gastro-theca )♦ The coverings of all 
the other parts receive names from the Greek words 
for these parts compounded with theca ; thus the 
