CHAPTER XIII 

 THE ODONATA 



The Odonata are such large and noticeable insects that they have 

 received many common names, such as dragon-flies, snake-doctors, 

 devil's darning needles, snake-feeders, etc. They are most plentiful 

 near water, as in this they spend their early lives, though the larger 

 and more powerful members of the group are frequently seen flying high 

 in the air and at some distance from their more usual habitat. 



The dragon-flies have rather long, slender bodies, the abdomen being 

 less shortened by the fusion and telescoping of its segments than in 

 most insects. The head is large, generally rather spherical, though con- 

 cave behind, and a great part of its surface is occupied by two very large 

 compound eyes, each of which in some species, contains more than 

 30,000 facets. As these insects are carnivorous and capture their prey 

 as it is flying, the advantage of large eyes which are also because of the 

 curvature of the surface of the head, capable of seeing in almost every 

 direction, is evident. There are also three ocelli. The antennae are 

 short and not very noticeable. 



The mouth parts, which are of the chewing type, are large and well 

 developed. The food appears to be captured by the legs and held by 

 them while it is being eaten. 



Four wings are present, all of about equal size, though the hinder 

 pair are somewhat larger except in the section known as the Damsel- 

 flies. The main veins are stout and are connected by many cross-veins. 

 Near the middle of the costa of each wing is a slight notch called the 

 nodus, at which point there is a particularly stout cross-vein. When at 

 rest the wings are held either nearly vertical over the body (damsel-flies) 

 or extended laterally, much as in flight. The metamorphosis is by pro- 

 gressive changes at times of molting, and though the nymph can hardly 

 be said to ever greatly resemble the adult, development may be con- 

 sidered as being by an incomplete metamorphosis. 



The Odonata may then be characterized as: 



Insects which as adults usually have long, slender bodies, large heads and 

 large eyes: wings four, membranous, the hinder pair as large or larger than 

 the front pair, and each has near the middle of its front margin a notch, 

 somewhat resembling a joint, called the nodus: mouth parts for chewing and 

 well developed. Metamorphosis incomplete. 



There are two groups of dragon-flies. In one the insect is slender, 

 the two pairs of wings are of about equal size, and when not in use are 



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