64 



THE ANATOMY OF THE HONEY BEE. 



anterior end of this great longitudinal muscle is a thick mass of 

 dorso- ventral fibers (VAIcl) extending from the lateral areas of the 

 mesoscutum (Set.,) to the lateral parts of the mesosternum {S.^). A 

 contraction of the vertical muscles must depress the tergal parts, 

 at the same time expanding the entire thorax in a longitudinal direc- 

 tion and stretching the longitudinal muscles. A contraction, then, 

 of the latter muscles (LMcl) restores the shape of the thorax and 

 elevates the tergal parts. Remembering, now, that the wings are 



supported from be- 

 low upon the 

 pleural wing proc- 

 esses and that each 

 is hinged to the 

 back by the notal 

 wing processes, it 

 is clear that a de- 

 pression of the 



LMcI, 



dorsum of 

 thorax must 



the 

 ele- 



vate the wings and 

 that an elevation 

 of the dorsum de- 

 presses them — the 

 pleural wing proc- 

 esses acting as the 

 fulcra. Hence, the 

 chief up-and-down 

 movements of the 

 wings are pro- 

 duced by these 

 great thoracic mus- 

 cles acting upon 

 the shape of the 

 thorax as a whole 

 and not directly 

 upon the wings 

 themselves. The vertical muscles are the elevators and the longi- 

 tudinal the depressors. 



But besides being moved up and down the wings can also, as before 

 stated, be extended and flexed, i. e., turned forward and backward in 

 a horizontal plane upon the pleural wing process. The muscles 

 which accomplish these movements lie against the inner face of the 

 pleurum (fig. 28), and each wing is provided with a separate set. 

 The extensor muscle {PMcl) is the most anterior and is inserted by 

 a long neck upon the preparapterum {^P). The latter is closely 



Fig. 27. — Median section through thorax of drone, showing 

 longitudinal muscles (LMch) of mesothorax going from 

 mesotergal scutum (Scfe) and small anterior phragma 

 (Aph) to posterior phragma (Pph^) of Internal postscutel- 

 lum (postnotum) of same segment, also showing vertical 

 mesothoracic muscles (FJfcO, and ventral longitudinal mus- 

 cles (Imcl), and longitudinal muscles of metathorax 

 (LMch) going from postphragma of mesothorax (Ppha) to 

 posterior edge of propodeum or first abdominal tergum (IT). 

 By alternate contraction of dorsal longitudinal muscles and 

 vertical muscles, roof of thorax is elevated and depressed, 

 causing wings to heat downward and upward respectively, 

 being supported on fulcra formed by pleural wing processes 

 (fig. 28, WPi) of side walls of thorax. 



