NO. 7 MUSCULATURE OF COLEOPTERA DORSEV 1 7 



as also is the anterior dorsal dilator muscle of the pharynx, <j, and ihe 

 dorsal dilator muscle of the cibarium, 5. Hypopharyngeal bar Y 

 (fig- 57) is very weakly sclerotized. The labial muscles consist of 

 two pairs, the dorsal and ventral muscles of the labium, jo and Ji 

 (figs. 57, 58). 



The larvae considered from the family Ptilodactylidae are Ptilo- 

 dactyla serricollis (Say) (figs. 59, 60, 61). The ventral muscle of 

 the lahrum, ?, two dorsal dilator muscles of the cibarium, 6 and 7, 

 and the muscle of hypopharyngeal bar Y , 10 (figs. 59. 61). are present 

 and well developed. The dorsal and ventral muscles of the labium, 

 20 and 21 (figs. 60, 61), are present. Muscle 20 originates medially 

 at the inner base of the anterior tentorial arms; muscle 21 arises on 

 the base of the submentum between the posterior ends of the anterior 

 tentorial arms. 



XL CANTHAROIDEA 



Adults from two families in this group were studied. Chauliogna- 

 thus pennsylvanicus Deg., Cantharidae, and Plateros timidns Lee, 

 Lycidae. 



In Chauliognathus (figs. 62, 63, 64) the muscles are very well de- 

 veloped; those of the labrum, cibarium, pharynx, and hypopharynx 

 are massive (figs. 62, 63). The transverse compressor muscle group 

 of tJie cibarium, 12, is absent. Hypopharyngeal bar }' (fig. 62) is 

 continuous with the greatly modified tentorial structure that forms 

 a strong support to withstand the action of the powerful muscles of 

 this region ; it unites the dorsal and ventral head walls rigidly. One 

 side of the structure is joined with the other by means of a sub- 

 pharyngeal sclerotized area. The posterior (ventral) ends are con- 

 tinuous with the ventral head wall. The epipharyngeal region of the 

 labrum and the posterior dorsal labial region are equipped with a 

 lobe and a grooved receptacle respectively, similar to that already 

 described in the adult Silpha americana L., but in Chauliognathus it 

 is more definitely associated with the epipharyngeal area. The labial 

 muscles are much the same as those of the generalized form and are 

 not nearly so powerful proportionately as are those of the dorsal 

 head regions. Each lateral posterior margin of the labium is fur- 

 nished with a slender, sclerotized resilient bar, RB (fig. 62), which 

 abuts against the anterior external face of the rigid tentorial structure. 

 This resilient bar probably assists the labium in returning to its nor- 

 mal resting position after contractions of the labial muscles have 

 disturbed its position. 



