MECHANISM OF FEEDING IN HEMIPTERA — QADRI 24I 



by two muscles — namely, protractors — which arise from the loral 

 plate near their junction with the mandibular plate. They are at- 

 tached to the outer arm of the stylet. The other muscles are retractors 

 and are inserted on the inner arm of the base of the stylet. 



The labium of Homoptera is comparatively less well known. The 

 works of special importance are those of Weber and Butt. In 

 Idiocerns, the labium is 3-jointed with a basal gular plate. It is 

 deeply grooved in order to lodge the stylets. At its base the labium 

 is provided with a sclerotized plate which is produced posteriorly as 

 an apodeme. It is bifurcated anteriorly. This plate provides the 

 basis of attachment of the muscles of the labium and plays an im- 

 portant part in its movement. The apical segment of the labium in 

 Idiocerus, as well as in Pyrilla, provides the clasping mechanism. In 

 Idiocerus there is a pair of processes which form a sclerotized arch 

 over the lateral groove. In Pyrilla (fig. 6) there are well-developed 

 clasps in the form of hard pieces supported at their bases by the proc- 

 esses of the apical segment. The internal muscles of the labium con- 

 sist of transverse or oblique fibers arising from the ventral wall in 

 the region of the second segment and are helpful in deepening the 

 groove of the labium and bringing about the clasping of the stylet. 

 The external muscles of the labium consist of two sets. One of them 

 arises from the head capsule and is inserted on the lateral plate. The 

 other muscle arises from the apodeme of the labium and is inserted 

 between the junction of first and second labial segments. The former 

 works as the elevator of the labium and the latter as its depressor. 



HETEROPTERA 



Some salient features of the anatomy of the head capsule and mouth 

 parts in Heteroptera are as follows : 



The dorsal wall of the head capsule in Heteroptera is neither frons 

 (Becker, 1929) nor clypeus (Rawat, 1939, and Weber, 1954) but 

 frons-postclypeus (Butt, 1943). In Coridae, however, frons and 

 clypeus are separate. 



The hypopharynx in Notonectidae and Corixidae is provided with 

 rail-like ridges fitting in the maxillary stylets in order to give addi- 

 tional strength to their movements. Also there is a longitudinal groove 

 to fit on a mandibular stylet ridge. These supports are extremely 

 helpful in feeding. 



Mandible (figs. 7, 8, and 9. — The mandibular stylet and lever are 

 articulated with the head capsule. The mandibular stylets are shorter 

 than the maxillary stylets and are provided with recurved spines at 



