280 
HALF HOURS WITH INSECTS. 
[Packard. 
means of the two long terminal spines terminating its up¬ 
turned extremity it holds the old cast skin over its body 
like an umbrella. The beetle itself in its resplendent golden 
hues has been compared, by Wallace, to “glittering dew- 
drops upon the leaves.” In another form, Chelymorpha crU 
braria (Fig. 217; a, pupa), which is considerably larger than 
Cassida, and feeds very much exposed on the silk weed, and 
sometimes on the raspberry, is also protected by its cast 
skin, though in a less degree. 
The larva of the common potato beetle of the eastern 
states (Fig. 218; a, larva; 6, c, pupa; d, eggs) covers its 
dull gray soft body with a black mass of its excrement, 
Fig. 217. Fig. 218. 
which is at once a protection from the heat of the sun and 
the attacks of birds, which probably regard them as any¬ 
thing but living and edible insects. 
It would seem, then, that while in the generality of cases 
insects harmonize in color and often in form with surround¬ 
ing objects, or even distinctly mimic natural objects, this is 
owing in all probability mainly to the physical environment 
of the animal; in a few cases, however, there is an appear¬ 
ance of design, and natural selection has been the means 
by which the mimicry has been effected and the species 
preserved. 
24 
