THE EMBRYOLOGY OF THE HONEY BEE 191 



The muscles included in the head comprise the gnathal muscles, 

 moving the mouth parts, the muscles attached to the tentorium 

 (already described under the section relating to that structure) 

 and certain muscles which although having their origin on the 

 endoskeleton of the head belong properly to the alimentary canal. 



The muscles of the newly hatched larva are by no means so 

 easily identified as in older larvae, being less well differentiated. 

 Moreover in so small an object the study of sections is the only 

 method available. In older larvae both mandibles and maxillae 

 are provided with flexor and extensor muscles, those of the mandi- 

 bles being much the larger. In newly hatched larvae, however, 

 the only gnathal muscles clearly evident are the flexor muscles 

 of the mandibles. These are relatively large muscles, each of 

 which is inserted on the mandibular apodeme, whence it passes 

 dorsad, caudad and ectad, spreading out fanwise meanwhile, to a 

 broad origin on the inner surface of the dorso-lateral face of the 

 head capsule behind the optic lobes and near the junction of the 

 head and trunk (Fig. 42, RMcl). 



The principal muscles of the trunk comprise dorsal and ventral 

 longitudinal muscles and oblique muscles. The dorsal longitu- 

 dinal muscles (Fig. 75, DLMcl) are broad flat sheets compris- 

 ing one layer of fibres, and lie on either side of the heart, 

 beneath the dorso-lateral hypodermis extending far down on the 

 side. A pair of these are situated in every segment, their ends 

 being attached to the intersegmental hypodermis, as shown in 

 figure 73A. 



The ventral longitudinal muscles (Fig. 75, VLMcl) correspond 

 in their arrangement and function to the dorsal longitudinal mus- 

 cles, but are only about half as wide. They extend laterally from 

 the ventral nerve cord about half way up to the level of the 

 longitudinal tracheal trunk. 



The oblique muscles (Fig. 75, OMcl) comprise a pair of mus- 

 cles spanning the lateral wall of each segment and arranged in 

 such a way that if seen in side view they would together form a 

 figure resembling the letter X. The smaller of these lies close to 

 the hypodermis, and runs dorsad and cephalad, while the larger is 

 situated a short distance within and runs ventrad and cephalad. 

 In addition to the oblique muscles there are delicate muscles, 



X 



