NO. 7 MUSCULATURE OF COLEOPTERA — DORSEY IS 



chroidae, larvae were studied. In Scotohates (figs. 44, 45, 46) the 

 muscles are well developed. The compressor muscle of the labrmn, 

 I, the dorsal dilator muscle of the pharynx, 11, and the compressor 

 muscle group of the cibariuin, 12, are absent. The dorsal dilator 

 muscles of the ciharium, 5, 6, and 7 (figs. 44, 46), have become 

 grouped together and are indicated only by 7. The muscle of hypo- 

 pharyngeal bar Y , 10 (fig. 44), has numerous subdivisions. There 

 is a large, heavily sclerotized median cuspidate sclerite (CPS) on 

 the dorsal surface of the hypopharynx (fig. 46). An arm extends 

 posteriorly and ventrally from each side of the posterior region of 

 this sclerite to become joined to a heavily sclerotized intralabial brace 

 the lateral limits of which are the sides of the posterior hypo- 

 pharyngeal region. The ventral muscle of the labium, 21 (figs. 45, 

 46), arises and is inserted in the usual manner; the dorsal muscle of 

 the labium, 20 (fig. 46), arises in the posterior lateral region of the 

 submentum just anterior to the posterior end of the anterior tentorial 

 arm. The muscle of the prementum, 22 (fig. 45), is a broad, powerful 

 muscle. 



In Hippodamia only the ventral muscle of the labium, 21, is present. 

 The ventral muscle of the labrum, 3, is absent ; the tormae are slender 

 and rodlike and extend posteriorly to become united with hypopharyn- 

 geal bar Y. The dorsal dilator muscles of the pharynx, p and 11, are 

 especially powerful. 



In Synchroa the musculature is similar to that of Scotobates though 

 the compressor muscle group of the cibarium, 12, is present and the 

 muscle of hypopharyngeal bar Y , 10, is not so profusely branched. 



VIII. BYRRHOIDEA 



Only larval forms were available for study in the family Byrrhidae. 

 In Byrrhus (figs. 47, 48, 49) the labral muscles are absent. The dor- 

 sal dilator muscles of the cibarium, 5, 6, and 7 (figs. 47, 48), are re- 

 duced in size and are grouped together. The dorsal dilator muscle of 

 the anterior region of the pharynx, p (figs. 47, 48), is small; the 

 muscle of hypopharyngeal bar Y, 10 (figs, 47, 48), consists of two 

 large branches, 10 and 10 A. The labial muscles are somewhat con- 

 fusing because of an additional labial muscle, 22A (figs. 48, 49). 

 The regular labial muscles, 20 and 21, occur as usual and the muscle 

 of the prementum, 22 (figs. 48, 49), is consistent. The additional 

 labial muscle, 22 A, may be a second muscle of the prementum inserted 

 at the base of prementum i (figs. 48, 49). 



