CHAPTER XXI 

 ORDER HOMOPTERA* 



Cicadas, Leaf-Hoppers, Aphids, Scale-Bugs, and others 



The winged members of this order have four wings, except in the 

 family Coccidce; the wings are of the same thickness throughout, and 

 usually are held sloping at the sides of the body when at rest. The 

 mouth-parts are formed for piercing and sucking; the beak arises from 

 the hind part of the lower side of the head. The metamorphosis is gradual 

 except in some highly specialized forms. 



Although the Homoptera is a well-defined order, the families of 

 which it is composed differ greatly in the appearance of their members. 

 For this reason there is no popular name that is applied to the order 

 as a whole. 



The Homoptera was formerly regarded as a suborder of the Hemip- 

 tera, that order being divided into two suborders, the Heteroptera 

 and the Homoptera. But these two groups of insects differ so mark- 

 edly in structure that it seems best to regard them as distinct orders. 

 The Hemiptera is, therefore, restricted to what was formerly known 

 as the suborder Heteroptera, and the suborder Homoptera is raised 

 to the rank of a separate order. 



The wings of the Homoptera are usually membranous, but in 

 some the front wings are subcoriaceous. In these cases, however, the}^ 

 are of quite uniform texture throughout, and not thickened at the 

 base as in the Hemiptera. 



Many wingless forms exist in this order; in the family Coccidas 

 the females are always wingless; and in the family Aphididas the 

 males may be either winged or wingless, while the sexually perfect 

 females and certain generations of the agamic females are wingless. 

 In the Coccidae the males have only a single pair of wings, the hind 

 wings being represented by a pair of club-like halteres. Each of 

 these is furnished with a bristle, which is hooked and fits in a pocket 

 on the hind margin of the fore wing of the same side. 



In several of the families of the Homoptera the wing-venation is 

 greatly reduced ; and even in the case of the more generalized forms, 

 if only the wings of adults be studied the venation of these wings 

 appears to depart widely from the hypothetical primitive type; 

 but by examining the tracheae that precede the wing-veins in the 

 wings of the nymphs, it is easy to determine the homologies of the 

 wing-veins. This has now been done in the case of representatives of 

 each of the families. The most generalized condition was found in 

 the wings of a cicada, which will serve as the type of homopterous 

 wing-venation. 



*Hom6ptera: homos (6fj.6s), same, pteron (irTepdv), a wing. 



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