OPHIOGOMPHUS 67 
The nymphs frequent trashy shores, preferably in running water. 
Several different sizes of nymphs are usually found together, indicating 
that a number of years are probably required for development. The 
grotesque cast skins left behind at transformation, sticking to logs 
and trash, are usually within a foot of the water’s edge. 
8. OPHIOGOMPHUs Selys 
These are stream-haunting dragonflies of moderate size and of green- 
ish or gray-green coloration. The inferior appendage of the male is 
large and four-lobed, and the occiput of the female usually bears 
sharp thorn-like horns.* The triangles are all free from cross veins. 
The anal loop is semicircular and well defined posteriorly by conver- 
gence of veins A; and A, and a connecting cross vein. Usually it is 
divided into three cells. 
This is a holartic genus with a score or more of species, most of which 
are North American. The adults are often locally abundant, but they 
are of elusive habits and are not commonly collected. They are singu- 
larly difficult to see as they flit about the rapids that are their breeding 
places. 
Kennedy carefully studied this genus in the mountains of the Pacific 
slope. He says of it (17, p. 529): 
The imagoes of the various species spend the greater part of their time seated 
on gravel bars from which they fly up at intervals to catch insects or to intercept 
individuals of their own kind. They are rarely found far from running water. 
Copulation is a lengthy affair. The male usually captures the female as she 
flies along the water’s edge on her business of oviposition, when he grasps her 
head with his feet and then, bending his abdomen forward, grasps her occiput 
with his claspers while freeing his feet. She in the meantime bends her abdomen 
forward and copulates. After a short nuptial flight the pair settles on some bush 
and remains in copulation many minutes. In ovipositing the female deposits 
the eggs in swift water, usually on rapids, where she flies back and forth dipping 
the tip of her abdomen in the stream. Though the 
eggs are laid on the shallow rapids, the nymphs 
during the latter part of their life live in the mud- 
dier bottom of the quieter water, for the exuviae 
are usually found along the edges of the deeper 
pools. 
The nymphs of Ophiogomphus are shallow 
burrowers in the sandy or gravelly beds of 
clear flowing streams and lakes. They are 
Fic. 28. Tip of labium of always silt covered and inconspicuous. They 
Ophiogomphus, with its gree in having a rather short stocky body 
laterallobe moreenlarged. with divergent wing cases, and abruptly 


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* Whence such specific names as O. bison and O. spinicorne. 
