i6 



HOMOPTERA 



and slightly nearer than the ocelH to the epicranial suture. The base of each maxilla is swollen to 

 form a cylindrical club, which represents in length about one-third of that part of the maxilla inclosed 

 in the head proper. The entire seta is uniformly cylindrical and smooth. It often extends for some 

 length beyond the tip of the labium when extruded. The tip shows some variation, but in most forms 

 it is gradually acuminate to a very sharp extremity. In one species of the genus Thelia the tips of the 

 maxillse show a bifurcate condition, and in the genus Gargara they appear to be curled but it is doubtful 

 if this has any anatomical significance. 



The mandibles originate hkewise from the vertex, but from a point latero-ventrad of the ocelli. 

 The base is broadly swoUen and bicipital at its junction with the skeleton of the head. Like the 

 maxilla, the mandible is extended in the form of a long, bristle-hke seta ; but, unlike the maxiila, this seta 

 is not cylindrical but is flat and lance-like. The extremity is produced into a blade, which is smooth on 

 the outer and sinuate on the inner edge. In length the mandibles and maxillas are about equal. 



It will be noted that the attachment of the mandibular and maxillary setae to the vertex does not 

 agree with the conclusions reached in regard to other insects, in which these organs originate from the 

 postgenae. In a large number of dissections of the membracids, however, this structure seems to remain 

 constant. Whether this condition represents a more or less specialized arrangement, or whether it is 

 a result of a migration of organs, can be determined only by further investigations. The position of 

 the base of the mandibles as here described has been found to vary only in a few of the species of one 

 subfamily — the Membracinie In this group it apparently arises from the upper part of the clypeus. 

 This may represent a still further migration or a migration in a different direction from the generalized 

 condition. 



The head structures described in the preceding paragraphs are diagrammatically shown in the 

 following ligure : 



'Verfex 



C/ypeus 



^Gena 

 \ '"LaJbrum 

 .^ ^€piphonfnx 



^Labiam 



Occ/put 



^Pojfejena 

 "^Labium 



— Occipuf 



-Vertex 



~ £ife 

 " ~Gena 

 "fbsfoena 

 'Cf^peuj 

 ~L abrum 



'£pipiTari^nx 



— Labium 



FiG. 2. — The membpacld head 



The Thorax. — Superficially the thorax presents the most striking and interesting part of the 

 exoskeleton. This is of course due to the remarkable development of the pronotum, which is character- 

 istic of the family. The promise of peculiar scleritic structure thus suggested is not fulfilled, however. 

 when the anatomy is studied. Aside from the unusual and oftentimes grotesque enlargement of the 

 prothoracic tergum, the general arrangement of the skeletal parts is comparatively simple and rather 

 easily determined. The prothorax is very weakly attached to the mesothorax and separates from this 

 segment easily. The mesothorax and the metathorax are firmly joined and the sclerites occasionally 

 overlap in such a fashion as to strongly unite these last two segments. On the whole the tergum of 



