Biology of the IMembracidae of the Cayuga Lake Basin 307 



of each sclerite is projected laterad in a broad disk which ahiiost entLrely 

 covers the hinder part of the eye. The inner edge bounds the occipital 

 foramen and the lower end fuses with the lateral margin of the labrimi. 

 The extreme ventral projection follows the line of the labrum on the 

 inner margin and the genae on the outer cephahc, and ends in an attenuated 

 point. t 



The occipital foramen, as will be noted from the foregoing, is an almost 

 circular opening, its edges lined with a thin connective-tissue membrane 

 which is continuous with a like membrane from the inner body wall of the 

 prothorax. This conjunctival membrane is of greater extent in the 

 nymph than in the adult. 



The rostrum, or beak, consists of a two-jointed labium containing the 

 bristle-like maxillae and mandibles. It is stout and heavy, and is better 

 developed in the nymph than in the adult. In the former it is rather 

 flesh}^ and swollen, in the latter it is harder and more slender. The length 

 of the rostrum has been used as a systematic character; but this character 

 not only is of very doubtful value, but is hard to determine owing to the 

 fact that the rostrum is carried flat against the ventral surface of the body. 

 It may be hardly longer than the labrum or it may extend caudad beyond 

 the hind coxae. This variation in length is, to be sure, great, but is not 

 constant. Neither within the genus nor within the species has this 

 character been found useful in systematic work. 



The labium in the JMembracidae does not differ essentially from that 

 organ in other Homoptera. It consists of two segments, the btisal segment 

 being two or three times as long as the distal. The labium is grooved and 

 bears within the groove the mandibular and the maxillary setae. The 

 entire organ is movable, and when the insect is feeding it projects downward 

 at right angles to the body. When not in use it is folded back between the 

 coxae on the median ventral line of the body. In every form studied, 

 the labimn has been found to be straight, and no cases have been dis- 

 covered in which the distal segment was bent forward as has been shown 

 to be the case in certain other Hemiptera. 



The maxillae are modified to form long, bristle-like setae. They originate 

 from the interior surface of the vertex above the ocelli, at a point about 

 midway between the ocelli and the margin of the occiput and slightly 

 nearer than the ocelli to the epicranial suture (Plate xxxii, 3, 15). The 



