Packard.] INSECTS OE THE POND AND STREAM. 133 
on the struggling worm, which is nailed to the leg by a spine 
opposite the end of the claw. Why its body is so long and 
linear in shape, w r c cannot imagine, unless for the purpose 
of concealment and protection, as its movements are labored 
and slow, as are those of Belostoma, its near ally, which, as 
Fig. 93. 
has been remarked by others, closely resembles a dead leaf, 
as it lies at the bottom of the pond in wait for its prey. 
So small a proportion of insects are aquatic that the 
question arises whether those that do live in our ponds and 
streams may not be the descendants of terrestrial forms. 
The ocean is the parent of all life ultimately, but only a 
5 
