f 



so. 3 INSECT llRAl) SNODGKASS I05 



The maxillary palpus consists of five segments (lig. 40 A, B, C. 

 Pip). The basal segment is provided with levator and depressor mus- 

 cles (B, E, I/, 18) arising within the stipes; each of the other seg- 

 ments has a single muscle arising in the first or second segment proxi- 

 mal to it. 



The muscles of a maxilla are as follows : 



10. — Promotor of the cardo (fig. 40 C). — A small fan of fibers 

 arising on lower posterior part of postgena, external and anterior to 

 the mandibular abductor ; inserted on slender apodeme of basal arm 

 of cardo. 



//. — Adductors of the cardo (fig. 40 B). — Two muscles arising on 

 posterior end of anterior arm of tentorium, extending ventrally, pos- 

 teriorly, and outward; one {iia) inserted on process {s) of inner 

 face of cardo, the other (iih) mesad to distal end of ridge (r) of 

 cardo. 



12. — Proximal adductor of the stipes (fig. 40 E). — Arising on ex- 

 treme posterior end of anterior arm of tentorium; inserted on ridge 

 of inner margin of stipes. 



7j. — Distal adductors of the stipes (fig. 40 E). — Two muscles 

 arising on tentorium, the first (13a) a slender muscle arising, along 

 with iia, lib, and 12, on posterior end of anterior arm of tentorium, 

 the second (isb) a large, thick, digastric muscle arising laterally on 

 concave ventral surface of body of tentorium ; both muscles inserted 

 on a slender apodeme attached to inner distal angle of stipes. 



Muscles II, 12, and 13 correspond with the adductors of the cardo 

 and stipes that in Apterygota arise on the hypopharyngeal apodemes 

 (fig. 30 B, KLcd, KLst), representing the sternal adductors, or ster- 

 nal promotor and remotor, of a primitive appendage (fig. 35 B, A', L). 



14. — Cranial flexor of the lacinia (fig. 40 B). — Arises on gena just 

 before upper end of promotor of cardo (C, 10) ; inserted on inner 

 angle of base of lacinia. This muscle is the homologue of the cranial 

 flexor of the maxillary lacinia in Apterygota (fig. 30 B, /?cc), and of 

 the corresponding flexor of the mandibular lacinia in Myriapoda (fig. 

 26 A, B, Cflcc). 



75. — Stipital flexor of the lacinia (fig. 40 B). — A large two- 

 branched muscle arising in base of stipes, one branch {13a) medially, 

 the other (ifib) in outer basal angle ; both inserted on anterior margin 

 of base of lacinia. These muscles flex the lacinia forward. Berlese 

 ( 1909) describes the posterior branch of this muscle in Acridium as 

 attached to the posterior wall of the lacinia, and as being an antagonist 

 to the anterior branch, but in no insect has the writer observed an 

 antagonist to the lacinial flexor. 



