398 



AN INTRODUCTION TO ENTOMOLOGY 



CO " 



published accounts of the head of homopterous insects the clypeus 

 has been incorrectly identified as the front. 



The labrum (Figs. 462 and 463, /) is joined to the lower end of the 

 clypeus; at its distal end it forms a sheath covering the base of the 

 labium and the enclosed seise. This part is described as the clypeus 

 by those who have incorrectly identified the clypeus as the front. 

 The epipharynx (Figs. 462 and 463, ^) arises at its normal position 

 on the ental surface of the labrum; but it is greatly developed and 

 projects beyond the end of the labrum. The projecting part has been 



mistaken for the labrum by 

 some writers, those who 

 have failed to recognize the 

 front and have termed the 

 clypeus the front and the 

 labrum the clypeus. 



The mandibular sderites 

 are easily recognized in the 

 cicada. On each lateral as- 

 pect of the head there are 

 two quite distinct sclerites; 

 the one that is next to the 

 clypeus and the base of the 

 labium is the mandibular 

 sclerite(Figs.462and 463,:?;). 

 This sclerite is termed the 

 lora by some writers on the 

 Homoptera. 



The mandibular sclerites 

 are believed to be in each 

 case the basal part of a man- 

 dible. They were first rec- 

 ognized as such by Profes- 

 sor J. B. Smith ('92); and 

 this conclusion has been 

 adopted by Marlatt ('95), 

 Heymons ('99), Meek ('03), 

 Berlese ('09), and Bugnion 

 and Popoff ('11). On the 

 other hand, Muir and Ker- 



Fig. 465. — Caudal view of the head of a cicada, 

 with part of the head-capsule and muscles re- 

 moved so as to show the left mandible and 

 the right maxilla. (Prom Meek.) 



shaw ('12) regard the loree as "lateral developments of the clypeal 

 region" and not parts of mandibles. 



The structure of the mandible as a whole has been worked out by 

 Meek ('03) and is shown in the left half of Figure 465. Within the 

 cavity of the head the maxillary seta is enlarged, and to it are attached 

 a retractor muscle (mdr) and a protractor muscle (mdp). The seta is 

 attached to the dorsal end of the mandibular sclerite (Fig. 465, mds) 

 by a quadrangular sclerite (Fig. 465, co). 



The maxillary sderites (Figs. 462 and 463, y) are closely parallel 

 with the mandibular sclerites, but extend farther down, joining the 



