132 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 89 



arise on posterior dorsal angle of quadrate plate of ninth tergum, and 

 cover both surfaces of dorsal apodemal part of the plate; insertion 

 anteriorly on upper extremity of ramus of second valvifer {r2vl). 

 Fibers of ventral group {i/h) arise posteriorly on inner face of quad- 

 rate plate, and lie parallel to those of dorsal group ; insertion anteriorly 

 on anterior arm of second valvifer (oblong plate). 



Much confusion has existed as to the insertion points of these 

 muscles. Sollmann (1863) correctly gave the insertion of the upper 

 muscle on the extremity of the ramus of the second valvula, but the 

 lower muscle he wrongly described as attached on the first valvifer 

 (Winkel) ; Kraepelin (1873), on the other hand, erroneously ascribed 

 the dorsal muscle to the first valvifer, but correctly described the at- 

 tachment of the lower one on the second valvifer. Kraepelin's error 

 has been followed by Zander (1911), Betts (1923), and Morison 

 (1927). The two groups of fibers in the bee very clearly correspond 

 with the usually single anterior tergal muscle of the second valvifer 

 (figs. 29, 34, 6). In some Hymenoptera, as in Megarhyssa (fig. 45 C), 

 they form two quite distinct muscles (i/a, lyh). These muscles are 

 the protractors of the lancets. 



18. Posterior tergal muscle of the second valvifer. — A broad, flat, 

 tergopleural muscle covering most of the inner face of quadrate 

 plate of ninth tergum, on which it arises dorsally and anteriorly (fig. 

 45 A) ; insertion ventrally on posterior part of dorsal ridge of 

 second valvifer (2Vlf). This muscle is the retractor of the lancet. 



In the queen a slender muscle arises dorsally on the posterior dorsal 

 angle of the quadrate plate, and is inserted ventrally on the second 

 valvula mesad of 18. This muscle is described by Morison (1927) 

 as a distinct muscle, but it is here regarded as a branch of 18, since 

 the two have the same insertion, and together would represent the 

 usual posterior tergal muscle of the second valvifer (figs. 29, 34, 7). 



ip. Muscle of the furcula. — ^A highly developed muscle in the bee 

 (fig. 45 A) , consisting of a wide layer of strong fibers arising ventrally 

 on most of length of inner surface of second valvifer (oblong plate) ; 

 fibers curve anteriorly, dorsally, and mesally over ninth ventral mem- 

 brane (I XV) to insertion on stem and upper part of arm of furcula 

 (Frc). This muscle is much smaller in lower Hymenoptera; in the 

 braconid Atanycolus it is inserted directly on a small basal swelling 

 of the united second valvulae (B, ig) ; in the ichneumonid Mega- 

 rhyssa (C, Ip) it is attached on a short ligamentous process arising 

 from a hooked dorsal extension of the base of the united second val- 

 vulae ; in the tenthredinid Pteronidea, a corresponding muscle arising 

 on the second valvifer is inserted on a long basal process of the 



