36 HAWK-MOTHS. 
caterpillar enters the earth, where it forms a smooth cavity, 
inside of which it transforms to a light-brown pupa. The 
caterpillars vary very much indeed, so much so that ex- 
treme forms of it do not resemble each other in the least. 
The most common form is yellowish-green, with a promin- 
ent sub-dorsal row of elliptical spots, each spot consisting 
of two curved black lines inclosing a bright crimson space 
and a pale vellow line; all the spots are connected by a pale 
yellow stripe, edged above with black (Fig. 34). The other 
Fiy. 35.—Deilephila lineata Fab., caterpillar. 
common form is black, distinguished chiefly by a narrow 
yellow line along the back, and a series of paler and darker 
yellow spots (Fig. 35). Both forms are subject to great 
variation. 
These rather beautiful caterpillars are sometimes exceed- 
ingly numerous, and people are apt to become scared on 
their account. When army worms and migratory locusts 
have denuded fields of almost all plants, only the purslane 
is left in undisturbed possession of such fields, not having 
been eaten by either of the above insects, and having now an 
opportunity to spread, this weed is not slow to do so, and in 
this way a large amount of food ‘is offered to and accepted 
by this insect. But an increased number of caterpillars is 
