CORDULEGASTER 153 
triangular, concave, and bear a row of short raptorial setae just within 
the external margin, a stouter, but not longer movable hook at the end 
of this row, and a series of coarse, irregular interlocking teeth on the 
distal margin. 
Prothorax with a transverse dorsal flattened area, which is fringed 
with stiff hairs; legs slender and not very long, adapted for raking the 
sand aside; femora and tibiae with dorsal and ventral rows of long 
hairs, the ventral row on the tibiae graduating into spines at the tip, 
these becoming arranged in a double row on the ventral side of the 
tarsal segments; tarsi three-jointed; wings a little divergent on the two 
sides, when grown, reaching the fourth abdominal segment. 
Abdomen, subcylindric, arcuately upcurved toward the tip; no dorsal 
hooks; lateral appendages less than one fourth as long as superior and 
inferiors; the transverse apical rings on the abdominal segments are 
somewhat remote from the apices of the segments and bear rows of very 
stiff hairs, which are incurved at the tip and serve to hold a layer of 
sand, dirt, etc. about the body. 
The nymphs live on the bottom in shallow water, buried in clean 
sand or in silt. Though buried they do not burrow, but descend by 
raking the sand from beneath them by sweeping, lateral movements of 
the legs. When deep enough, they kick the sand up over the back till 
only the elevated tips of the eyes and the respiratory aperture at the 
tip of the abdomen are exposed. By placing a live nymph in a dish of 
sand and water and watching, its method may be observed in a very few 
minutes. The whole comical performance reminds one strongly of the 
descent of an old hen in a dustbath (whence the common name sug- 
gested for this group). 
Once adjusted in the sand, a nymph (unless food tempts) remains 
motionless a very long time, even for weeks. Let any little insect walk 
or swim near the nymph’s head, and a hidden labium springs from the 
sand with a mightly sweep and clutches it. The nymphs will capture 
and eat young brook trout as long as themselves, when placed in their 
cage. So eager are they, they will rise partly from the sand on approach 
of a trout. Like the nymphs of the Aeschninae, they seem to have a 
decided preference for big game, if one may judge by the strenuous 
efforts they put forth when something at the limit of their capacity for 
capturing approaches. 
KEY TO THE SPECIES* 
Adults 
1 Abdomen with transverse yellow bands on the segments...... 2. 
Abdomen with yellow spots... . 00... 20.0.2 ese ie Pee ss 4, 
