88 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IO3 



and thus expands the abdomen dorsoventrally. The other lateral 

 muscles pull the tergal and sternal plates together and are therefore 

 compressors of the abdomen. The entire musculature of the pre- 

 genital segments is operative in respiration, since the abdominal 

 breathing movements of the bee are both dor so ventral and longi- 

 tudinal. The same muscles, however, produce various other move- 

 ments of the abdomen, and it would appear that the dorsal and ventral 

 muscles, or the lateral muscles of opposite sides may act either in 

 unison or as antagonists. Finally, it should be noted that the external 

 dorsal and ventral muscles in the more anterior segments of the 

 abdomen (fig. 28 A, 126, 1^2, 755) run obliquely or transversely 

 between the adjoining segmental plates, and thus evidently produce 

 a partial rotary or torsion movement of the anterior segments on 

 each other. 



The musculature of the petiole segment (fig. 28 A, //) is simplified 

 by the absence of the first and second lateral muscles and, in the 

 worker, of the lateral internal ventral, though this muscle is present 

 in the drone (fig. 29 B, 131). 



In segments VII, VIII, and IX the musculature is progressively 

 reduced and altered as these segments become involved in modifications 

 adaptive to the reproductive functions. In the drone (fig. 29 B) seg- 

 ment VII retains the typical dorsal musculature, but the second pair 

 of lateral muscles is absent, and the sternum has on each side only a 

 small lateral internal muscle (B, D, 186) attached posteriorly on the 

 long anterior apodemal arm (&) of sternum VIII. In segment VIII 

 of the drone there is on each side a single, short dorsal muscle (B, 

 i8y) attached posteriorly on the apodeme of the ninth tergal sclerite 

 (IXT), one lateral muscle {191), and a short lateral internal ventral 

 (B, D, 7p5) between the eighth sternum and the small parameral 

 plate {Ip) of the genital apparatus. Segment IX has only one pair 

 of short dorsal muscles (B, 202) from the apodemes of the ninth 

 tergal plates to the base of the proctiger at the sides of the subanal 

 plate, but there are two small phallic muscles on each side (D, 203, 

 204) arising ventrally on the parameral plate (Ip) and attached 

 dorsally on the arm of the penis valve (pv), while finally a long, 

 slender muscle (20 j) goes from the arm of the penis valve to the 

 mucus gland, to which it is attached just laterad of the termination 

 of the vas deferens. 



In the female the musculature as well as the structure of the pos- 

 terior abdominal segments is very different from that of the male. 

 The tergal musculature of segment VII in the worker includes on 

 each side an internal dorsal (fig. 28 C, lyS) attached on the upper 



