ODONATA. 
127 
antennae and biting montliparts of a peculiar type. The lower 
side of the head is concealed by a development of the lower lip, in the 
form of a long jointed arm-like structure, which folds down over the 
mouth and which is armed at the tip with processes bearing strong 
spines. This jointed arm extends very rapidly to a considerable length 
seizes the prey and withdraws it to the mouth, where are the sharp max- 
ills and mandibles with which the prey is devoured. Like other aqua¬ 
tic larvae, these must obtain a supply of air and as they live below the 
surface, this air must be obtained from the water. This is effected in 
the Libellulinae and Aeschninae by taking water into the rectum, the 
Fig. 54.—= Alimentary^C-ANal AND TRACHE/E of aeschnid nymph. 
posterior portion of the alimentary canal, which is modified to act as a 
gill and to extract air from the water ; this part of the alimentary canal 
is penetrated by tracheae, into which the air is absorbed and which dis¬ 
tribute it as in other insects. (Fig. 54) The nymphs can be seen to 
take in and eject water from the hind end, 
the violent ejection of water also serving to 
propel the nymph forward and assist it 
to obtain its prey. In the Agrioninae , 
the nymph is provided with three flat lamel¬ 
lar appendages at the apex of the abdomen, 
which function as gills. (Fig. 55). 
Like the adult, the nymph is predaceous, 
the teeming fauna of fresh water 'supplying 
it with an ample supply of food. When 
fullgrown, the nymphs climb up out of 
the water, the skin breaks along the 
dorsum, and the perfect insect emerges ; 
the 
are gradually developed out- Fjg.-sR— Agrionid larva. 
