128 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 89 



merely a movable apodeme contained in a membranous fold at the 

 base of the bulb. The homologues of the muscles inserted upon it in 

 the bee are attached in the braconid (fig. 45 B, ip) directly to a 

 bulbous enlargement of the base of the ovipositor, while in the 

 ichneumonid (C) they are inserted on a ligamentous stalk containing 

 a small U-shaped sclerotization. The depressor mechanism of the 

 shaft of the sting in the bee, therefore, is clearly a development from 

 a much simpler mechanism of the ovipositor in the lower Hymenop- 

 tera, but it appears to have no counterpart in other orders of insects. 



Muscles of the seventh segment and the sting. — Since the muscles 

 of the seventh and genital segments cannot all be certainly identified 

 with specific muscles of the preceding segments, they will be given 

 descriptive names by which they may be recognized ; they are desig- 

 nated on the figures with arable numerals. The numbered series of 

 muscles applies in full to the queen only, certain muscles being absent 

 in the worker. The Hst of muscles here recorded for the terminal 

 segments of the bee, 22 in all, is somewhat greater than that given 

 by Betts (1923) and Morison (1927). Certain other discrepancies 

 in the accounts will be noted at the appropriate points, as will also 

 a few additions and corrections that must be made in the descrip- 

 tion of the muscles of the sting as given by SoUmann (1863), 

 Kraepelin (1873), and Zander (1911). 



The following nine muscles belong to the seventh segment: 



J. First internal dorsal muscle. — A rather wide muscle in the 

 worker arising anteriorly on seventh tergum (fig. 43 B) ; extending 

 posteriorly and ventrally to dorsal lobe of spiracular plate. Smaller 

 in the queen (fig. 44 C), where its insertion on spiracular plate is 

 on dorsal margin of anterior lobe. 



2. Second inter)tal dorsal muscle. — Found only in the queen. A 

 slender muscle arising dorsally on lateral part of seventh tergum; 

 insertion ventrally on dorsal margin of spiracular plate above the 

 spiracle (fig. 44 C). Not described by Betts or Morison. 



J. External dorsal muscle (not shown in the figures). — A wide 

 muscle against outer face of spiracular plate, present in both worker 

 and queen. Origin ventrally near lower lateral margin of seventh 

 tergum ; insertion dorsally on upper margin of dorsal lobe of spira- 

 cular plate, as indicated in the figures (figs. 43 B, 44 C, 5). This 

 muscle is a protractor between the tergal plates of segments VII 

 and VIII. 



4. First lateral tergosternal muscle. — Origin posteriorly on lateral 

 part of seventh tergum external to spiracular plate (fig. 43 B) ; in- 

 sertion anteriorly on lateral apodeme of seventh sternum (A, B). 



