50 



Nymphs one third to one half grown are transversely banded 

 with brown across the head, across segments 4, 5, and 6 (some- 

 times 7), and across 9 and 10. These bands disappear with 

 subsequent molting, and the full-grown nymphs are of nearly 

 a greenish color variously mottled with brown. 



Family GOMPHID^. 



There is a marked "family resemblance" among the 

 nymphs of each dragon-fly family, and this is quite as true of 

 the present one as of any other. Its nymphs are all evident 

 gomphids, even Ha genius, broad and flat as it is. Their most 

 marked characteristic is the pair of thick, rough, four-jointed 

 antennae. The flat labium is built on the same plan as that of 

 the Agrionidw and uEschnido' — the mentum, nearly truncate in 

 front, bearing a powerful mandible-like pair of grasping arms, 

 carrying on the outer side beyond the middle a large movable 

 hook, the arms usually toothed within and ending in an 

 incurved point. The domain of these nymphs, except Hagenius, 

 is the muddy, sandy, or rocky bottom of various kinds of 

 bodies of water, according to species. They live amongst 

 fallen trash and sediment, burrowing shallowly along with the 

 tip of the abdomen turned up so as to reach the water, thus 

 enabling them to breathe while foraging in a stratum of great 

 biological richness. Their colors are similar to the mud and 

 sand in which they dwell, and are often obscured by a coating 

 of mud. The flattened body and stout legs are well adapted 

 for burrowing. The head is broad and more or less wedge- 

 shaped, the antenuEe, laid close upon the labrum, forming the 

 point of the wedge. The third antennal joint is much the 

 largest; the fourth, a mere rudiment. The legs are stout, the 

 two anterior pairs directed forward, their tibise armed at tip 

 externally with more or less well-developed burrowing hooks. 

 The hind legs are directed backward and used to push the body 

 forward. The anterior and middle tarsi are two-jointed, not 

 three-jointed as in other Odonata. The dorsal hooks and lat- 

 eral spines are rather feebly developed. 



