20 Annals Entomological Society of America [Vol. XIII, 



fibres, originating in the middle of the front immediately beneath 

 the median ocellus and inserted by a short tendon into the 

 base of the labrum, one on each side of the median line. 



The Adductors of the Labrum (Figs. 7 and 8, ad. Ibr.) Two 

 three-headed muscles inserted by means of a small tendon, 

 one in each of the basal angles of the labrum. The outermost 

 head is attached to the front near the inner side of the antenna, 

 the innermost near the median line adjacent to the origin of the 

 abductor, and the middle head midway between these two. 

 In some specimens only the outer and inner heads were present. 



The Mandibles are articulated with the epicranium by 

 means of a ginglymus joint permitting motion in one plane 

 only, consequently there are but two muscles, an adductor, 

 and an abductor. The Adductor of the Mandible (Figs. 4, 5 

 and 6, ad. md.) is a pyramidal complex muscle and, owing to 

 the fact that in the cricket the mandibles are strong crushing 

 jaws, is the largest and strongest muscle in the head. Its base 

 occupies the whole top of the head as far forward as the eyes 

 and upper edge of the brain. It is inserted into the inner angle 

 of the base of the mandible by means of a large tendon composed 

 of three flat transparent laminae (Fig. 4, t). 



The Abductor of the Mandible (Fig. 4, abd. md.) is smaller 

 and has its origin in the epicranium beneath and behind the 

 eye. It is inserted into the outer angle of the mandible by 

 means of a long flat tendon. 



The Maxillae. Owing to the segmented structure of the 

 maxilla, its muscles are more numerous and complicated than 

 those of the labrum and mandible. The Abductor of the Maxilla 

 (Figs. 12 and 14, abd. mx.) is a thick triangular muscle origin- 

 ating in the gena and postgena near the origin of the abductor of 

 the mandible. It is inserted by means of a long narrow three- 

 faced tendon into the inner angle of the second segment of the 

 cardo. The hinge on which the maxilla turns lies mesad of the 

 insertion of the tendon along the upper edge of the proximal 

 segment of the cardo (i. e., the edge near the letter Ci in Fig. 14). 

 The opening of the maxillae therefore causes a pushing upwards 

 of the outer portions of their bases (the outer edge of C2). 

 Conversely the upward pull given to this portion of the maxillae 

 by the contraction of the abductors causes them to open. 



There are two Adductors of the Maxilla which both take 

 their origin in the lower surface of the central plate of the 



