21 
has reared Gomphus nymphs, which do not feed so readily as 
others, on earthworms. As they are more or less ready to eat 
each other, they must not be crowded. Anar is especially 
unprincipled in this respect, and Gomphus is fond of libellulids. 
Recently emerged living imagos should be transferred, each 
with its cast skin (exuvia), to dry boxes for a short time, till 
their surfaces and wings gain firmness and their colors are 
matured. The imago and its exuvia should always be kept 
together. 
If the observer is able to keep a close watch on waters 
where nymphs occur, about the time of their emergence, and 
does not mind an early morning visit before breakfast for some 
larger species, he will be amply rewarded for his enterprise 
some day by discovering a large number in the midst of the 
processes of transformation, often of some species rarely taken 
on the wing and very desirable for exchange purposes. 
In all cases and by all means full notes of habits, food, 
flight, manner of oviposition, and the like, should be carefully 
recorded. 
CHARACTERS USED IN CLASSIFICATION. 
The Nymph.—The most important recognition characters in 
the head of the nymph are derived from the labium, the an- 
tenn, and the form and sculpture of the upper surface. The 
latter is useful in the separation of species and genera. If the 
tip of the labium, or mask, which covers the mouth like a hand, 
be grasped and drawn forward, the labium will straighten out, 
and may be kept from springing back again. Like the arm, it 
consists of two joints, the submentum and mentum, the end of 
the latter broad, bearing a pair of broad flattened appendages, 
the lateral lobes of the labium. ‘he mentum itself is called the 
median lobe. Kach of the lateral lobes bears outwardly, near its 
tip, a strong movable hook. In the Petaluride, Avschnide, and 
Gomphide the labium is flat, and applied to the lower surface 
of the head; the lateral lobes are somewhat mandible-like, 
bearing a row of fine short teeth on the terminal edge in the 
Petaluride, and on the inner edge in the other two families 
