ODONA TA. 



91 



Fig. ioo. — 

 Tracheal 

 gill of 

 Agrion, 



their rapidly moving wings throwing out gleams of metaUic 

 color as they go. Still more beautiful are they when at rest, 

 their wings wide-spread or folded together above the ab- 

 domen, and as rigid and motionless as if made of iridescent 

 glass; and their great compound eyes shining like gold or 

 precious stones. But for all their terrible names Dragon- 

 flies are entirely innocent of any harm to mankind. 

 They neither sew up people's ears, as northern chil- 

 dren think ; nor bring dead snakes to life, as colored 

 people in the South believe ; but they are very 

 fierce enemies to their insect kindred. Their long, 

 narrow, closely netted wings are strong, carrying 

 them swiftly ; and their jaws are powerful, and their 

 appetites good ; so it is an unfortunate insect that 

 falls in their way. 



The mother Dragon-fly lays her eggs in water or 

 fastens them to aquatic plants. The young as soon 

 as hatched swim off and hunt for some smaller creatures to 

 eat. They have strong legs and big jaws, and are real in- 

 sect ogres. The lower lip when extended reaches far out, 



and is armed with powerful hooks with 

 which to grab their prey ; but when fold- 

 ed up it is so large that it is called a mask 

 and gives the insect's face a comical re- 

 semblance to that of a bull-dog. These 

 nymphs have a peculiar method of breath- 

 ing. The caudal end of the alimentary 

 canal is lined with tracheae. The insect 

 alternately draws water into this cavity 

 and expels it ; and thus the air in these 

 trachese is purified, this part of the alimen- 

 tary canal acting as a tracheal gill. This 

 process also helps the insect in swimming, 

 . , for the water may be expelled with such 



Fig. ioi. — Exuviae of ^ *■ 



nymph of Dragon-fly. force that the wholc body is sent forward. 

 In some species the nymphs have also two or three large 



