32 DRAGONFLIES OF NORTH AMERICA 
invite seizure. They have more or less wedgeshaped heads, short 
thick close-laid antennae, and flattened scraper-like front tibiae. These 
are all adaptations for getting through the bottom silt. 

Fig. 14. Sprawlers and burrowers. a, Libellula; b, Cordulegaster; c, Gom- 
phus; d, an unknown Gomphine. Drawn by Olive Tuttle (Mrs. J. T. Lloyd). 
Some habits intermediate between those of sprawlers and burrowers 
will be discussed under the subfamilies Petalurinae and Cordule- 
gasterinae. 

Fig. 15. Labium of Cordule- 
gaster diastatops. 
STRUCTURES 
Perhaps the most remarkable feature 
of nymphal anatomy is the labium or 
lower lip. It is very much elongated, 
folded upon itself like a hinge at the 
base of the mentum and then folded 
backward beneath the head and thorax, 
the middle hinge resting between the 
legs. At the front end of the mentum 
it bears a pair of strong grasping lateral 
lobes that are variously armed with teeth 
hooks and spines. It is a grasping organ 
of altogether unique design. When 
extended, its full length is almost that 
of the fore leg. It is thrown out and re- 
tracted again with such swiftness that 
the eye cannot follow it. With it the 
nymph reaches for a victim, clutches it 
between the armed lateral lobes, and 
draws it backward right into the jaws. 
The hooks and spines hold; the jaws 
devour; and if fragments are let fall, 
they are retained on the mentum as 
on a tray. The labium is finally thrust forward a little and even 
these fragments are gathered up. This combination of hands, carving 
tools and serving table is highly efficient. 
