22 HOMOPTERA 



The thoracic structures described in the preceding paiagraphs are shown in the accompanying 

 diagram. 



The Wings. — Thestructure of the wings, their position, and the sclerites concerned in their 

 attachments have been discussed in a previous report by the writer (igiya) and the homologies of the 

 wing veins have also been made the subject of a special paper (igiS) so that these matters need not be 

 discussed in further detail except to call attention to a few particular points which have to do with 

 phylogeny and taxoriomy. 



It should be remembered that in the Homoptera the wings are folded against the body with the 

 costal margin downward. This makes an apparent, but not a real, reverse of the normal position 

 in insects. Theoretically the wing of an insect may be considered as in a plane projecting horizontally 

 from the pleural wall of the body, with the costal region extending directly cephalad. Supported in 

 such a position, the anterior part of the articulating surface of the wing is attached to the anterior 

 wing process of the notum and the upper wing process of the episternum, while the posterior surface 

 is attached to the posterior process of the notum and the postparapterum of the epimeron. Actually, 

 however, in most orders of insects the plane of the wing is more likely to be tilted upward, the costal 

 margin pointing slightly dorso-cephalad and articulating chiefly with the anterior notal process, while 

 the anal region extends ventro-caudad and finds its chief connection at tiie pleural wing process 

 between the episternum and the epimeron. 



In the Membractda, on the other hand, the costal margin of the wing appears on superficial exami- 

 nation to be attached to the upper extremity of the episternum — in fact it actually hes in a groove in 

 this sclerite when at rest — whiie the anal area is clearly folded against the lower margin of the notum. 

 This position, which is not pecuhar to the wings of the Membracida but is found in most famihes of the 

 Homoptera, causes a twisting and shifting of the parts of the wing base which requires special attention. 

 If the theoretical position as above described is considered the normal, the position of the membracid 

 wing may be conceived by imagining that the normal wing is first folded directly downward and then 

 bent backward until its long axis is parallel with the longitudinal axis of the body. This shifting of 

 position has resulted in a migration of basal structures which renders difficult the homologizing of parts. 

 In spite of the twisting, however, it is possible to reconcile to a large extent the shifted attachments as 

 shown in this family with the commoner interpretation of the wing base in other insects. It has been 

 noted, in the discussion of the pleural and tergal sclerites, that in the Membracida no anterior wing pro- 

 cess could be determined on the notum, while the posterior process was prominent. This is probably 

 explained by the fact that the anterior angle of the wing base has migrated away from its normal posi- 

 tion, making the anterior process unnecessary ; while the posterior angle has moved upward, increasing 

 the musculature of the posterior region. The principal point of attachment of the fore wing is a long, 

 curved, partly chitinized cord, fused along the costal and middle part of the wing base (the cephalo- 

 ventral margin when in normal position) and extending between the notum and the episternum into the 

 body cavity, where it is connected with the wing muscles. This cord supports and probably directs the 

 movement of that part of the wing which accommodates the bases of the costal, subcostal, radial, median 

 and cubiial veins. It is rather sharply set ofif, however. from the tissue of the wing proper by a deep 

 constriction. When the wing is separated from the bodj- it usually breaks along this line. The extreme 

 cephalic costal angle is supported by the dorsal margin of the mesothoracic episternum. When at rest 

 and folded against the body, the basal fifth or sixth of the costal margin is supported by the meta- 

 thoracic episternum, which is hollowed out to receive it. This deep groove is indeed very charac- 

 teristic of the family. 



The chitinized portions of the vving base seem to show three weakly developed axillary sclerites 



