GENERAL ZOOLOGY 



eyes of a dragonfly are unusually large, and this may be a factor in its 

 efficiency as a predator of other flying insects. The clumsy naiads of dragon- 

 flies are found crawling along the bottom in fresh water; in these immature 

 stages they are predators of small aquatic animals. Before the final molt 

 to adulthood, they climb along the stem of a plant into the air, and after the 

 adult emerges the cast skin of the naiad remains clinging to this support. 

 Damsel flies, members of a difTerent but related suborder, are smaller, more 

 delicate of body and wing, and less efficient in flight. The life cycle, way of 

 life, and general features are very similar to those of dragonflies. 



Order Orthoptera (straight wings) — locusts and their relatives, grass- 

 hoppers, katydids, crickets, cockroaches, walking sticks, and praying mantises. 

 In all of these, the mouth parts arc mandibulate, and the life cycle is 

 paurometabolous, with gradual metamorphosis. There are usually two pairs 

 of wings, the anterior pair being modified to form thick, tough covers for 

 the membranous posterior pair. 



Crickets and katydids resemble locusts sufficiently in their general external 

 features to be recognized at once as allied forms. The crickets that are most 

 familiar are the house and field crickets of the genus Gryl/us. The hind legs 

 are elongated for jumping, as in the locust. In many species the wings are 

 reduced in size, and some crickets are wingless. In connection with the 

 nocturnal activities of these animals, the antennae, which are long and 

 slender, are highly specialized as tactile organs. In males certain of the wing 

 veins are modified for the production of sounds. The mole cricket is a type 

 with strongly modified, shovel-like anterior legs which it uses in burrowing. 

 Katydids (Fig. 15.28) are like green grasshoppers with very long antennae; 

 the females bear conspicuous blade-like ovipositors. 



Walking sticks and mantids are interesting, the former because of their 

 striking mimicry of twigs, and the latter for their efficiency in destroying 

 other insects. The "praying mantis" possesses strongly modified anterior 

 legs which form a pair of deadly pincers; as it waits for its insect prey, the 

 mantis holds these appendages in an attitude suggestive of the folded hands of 

 a supplicant (Fig. 15.28). Like the dragonflies, these insects are wrongly 

 maligned as harmful; they are actually so beneficial in their capacity of insect 

 predators that mantises and their characteristic egg masses are protected by 

 law in many parts of this country. 



Order Hemiptera or Heteroptera (half-wings or different wings) — true 

 bugs, the only insects that may properly be called "bugs." Representative 

 examples are the cabbage bug, the squash bug, the assassin bug, and the 

 water boatman. The mouth parts of these insects are suctorial; the wings 

 overlap across the dorsal midline, and the anterior pair are thick at their 

 bases and membranous at their tips. The life cycle in all hemipterans is^ 

 paurometabolous. 



The squash bug, Anasa trislis, which is a pest upon squash and pumpkin 

 vines the country over, is perhaps best known by the disagreeable odor it emits 

 when handled. It is representative of the true bugs with their mouth parts 



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