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. Anax is especially 

 unprincipled in this respect, and Gonijj/iHs 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 Njpnpli. — The most important recognition characters in 

 the head of the nymph are derived from the labium, the an- 

 tennae, 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 ^uhmenfniti and mcntKtu, the end of 

 the latter broad, bearing a pair of broad flattened appendages, 

 the lateral lobes of the labium. The mentum itself is called the 

 median lobe. Each of the lateral lobes bears outwardly, near its 

 tip, a strong movable hook. In the Fetalur'ida', ^iJsehttiihe, and 

 GompJi'nhe 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 

 Petaluridie, and on the inner edge in the other two families 



