Packard.] 
INSECTS AS MIMICS. 
277 
to the ground among the leaves of the oak are covered with 
dead leaves, and the color of the cocoon when bare harmo¬ 
nizes with that of the soil or leaves. 
Aquatic insects are often nearly colorless, like the water 
they inhabit. Many water larvae are pale green, like the 
plants in which they hide. What excellent mimics the cad¬ 
dis worms and Ranatra and Belostoma are, we have previ¬ 
ously adverted to in the chapter on Insects of the Pond and 
Stream. To the cases there given might be added certain 
sluggish larvae like Psephenus (Fig. 215) and others, which 
Fig. 214. Fig. 215. 
Cocoon of the American Silk Worm. Psephenus. 
adhere to the under side of pebbles, and are thoroughly as¬ 
similated in color to the mud of streams and the shores of 
the sea. 
Much light may be thrown upon this subject by a study of 
cave animals. Here the harmony in color and often in form 
to surrounding objects is most striking and the causes are 
quite apparent. The cave insects becoming blind from the 
darkness of their subterranean abode, lose their colors and 
are assimilated to the colors of the stalactites on which they 
walk or the walls of the cave to which they cling. The 
ground beetles, instead of being dark like their out-of-door 
relations, here fade out to the color of the limestone sands 
over which they run. The harmony in form and color with 
the environments of their subterranean abode is as apparent 
as the. cause. 
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