INSECTA. 353 



eludes the most voracious and destructive insects, as the Locust, 

 Cockroach, &c. 



Those insects which have both pairs of wings membranous, trans- 

 parent, strengthened by numerous nervures, and finely reticulated, 

 form the order Neuroptera^ which includes the highest organised 

 insects, as the predatory dragon-flies. 



The insects which have four membranous wings simply veined, and 

 crossing each other horizontally when at rest, form the order Hyme- 

 iioptera : they undergo a complete metamorphosis, and include the 

 most useful of insects, e. g.^ the bee. 



The insects with four wings, more or less clothed with minute 

 scales, are called Lepidoptera : they 1^3 



undergo complete metamorphosis, 

 and include the most beautiful spe- 

 cies of the class, as the butterflies : 

 in one family of this order the wings 



are divided lengthwise intoanum- ^'^^9iWi§^^'^ 



ber of feathered pieces, which ra- 

 diate from the body like the stems pterophora. 

 of a fan {fig, 143). 



The insects which have the anterior pair of wings in the condition 

 of the hemelytra, form the order Hemiptera ; but certain genera 

 have the dense part of the anterior wings reduced to so small a strip, 

 that they are scarcely distinguishable, except by size, from the pos- 

 terior pair, and these insects constitute a section of the order termed 

 Homoptera. 



A few remarkable genera of insects have the anterior pair of 

 wings reduced to small or rudimental elytra, and the posterior pair 

 unusually large, and folded longitudinally, like a fan when at rest. 

 The anterior wings being reduced to minute appendages twisted 

 spirally, the Order has been hence termed Strepsiptera. The spe- 

 cies, in their larval state, are parasitic on the bee tribe. 



The order Diptera is characterised by the development of the an- 

 terior pair of wings into organs of flight, and the retention of the 

 hinder pair in the condition of minute clavate appendages, usually 

 called the " balancers." The prothorax and metathorax are rudi- 

 mental whilst the mesothorax is disproportionately large to form the 

 required space for the powerful muscles, which execute, through the 

 two anterior wnngs, the function of flight. 



In almost every Order of Insects there are species, or there are 

 individuals, as the females of particular species, w^hich are apterous ; 

 but since the time of Aristotle, who divided insects primarily into the 

 " winged," Ptilota, and the " wingless," Aptera, most of the hexapod 



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