308 : THE DRAGON-FLY. 
of the Dragon-fly. It is the labium, or under lip greatly 
enlarged, and armed at the broad spoon-shaped extremity 
(Fig. 1, x) with two sharp hooks, adapted for seizing 
and retaining its prey. At rest, the terminal half is so 
bent up as to conceal the face, and thus the creature 
crawls about, to all appearance, the most innocent and 
lamb-like of insects. 
Not only does the immature Dragon-fly walk over the 
bottom of the pool or stream it inhabits, but it can also 
leap for a considerable distance, and 
by a most curious contrivance. 
j a syringe-like apparatus lodged in 
the end of the body, it discharges a 
stream of water for a distance of two 
or three inches behind it, thus pro- 
pelling the insect forwards. This 
apparatus combines the functions of 
locomotion and respiration. There 
J are, as usual, two breathing pores 
(stigmata) on each side of the tho- 
rax. But the process of breathing 
seems to be mostly carried on in 
the tail. The tracheæ are here collected in a large 
mass, sending their branches into folds of membrane 
lining the end of the alimentary canal, and which act like © 
a piston to force out the water. The entrance to the 
canal is protected by three to five triangular horny valves 
(Fig. 2, 9,10, 2 a, side view, 2), which open and shut 
at will. When open, the water flows in, bathing the 
internal gill-like organs, which extract the air from the 
water. This is then suddenly expelled by a strong mus- 
cular effort. 
In the smaller genera, Agrion (A. saucium, Plate 9, fig- 
Fig. 2 b. 
