NO. 2 HONEY BEE — SNODGRASS 63 



third axillary sclerite and its muscles, but in the fore wing of the bee 

 the action of the third axillary appears to be assisted by the fourth 

 axillary and its lever. 



The basal region of the fore wing of the bee in the natural position 

 of extension (fig. 19 A) is rolled on itself in such a way that most 

 of the axillary area is deflected. There is hence an oblique fold in 

 the wing base extending from the head of the first axillary (lAx), 

 behind the second axillary and the median plate, to the upwardly 

 directed distal end of the third axillary (^Ax). The pull of the third 

 axillary muscles (H), therefore, simply revolves the sclerite mesally 

 and somewhat forward on its base and thus accentuates the fold al- 

 ready present, with the result that the distal part of the wing turns 

 backward. If the wing base were flat (D), as it is in most insects, 

 the action would not be essentially different, as can be demonstrated 

 by revolving the third axillary in the wing of a dead specimen. 



The part that the fourth axillary plays in the flexing of the fore 

 wing of the bees can be shown by depressing its lever (fig. 19 D, 

 axlv). The fourth axillary {4 Ax) is movably articulated on the 

 margin of the mesonotum and its distal end is pressed against the 

 axillary cord {AxC). The head of the lever lies in the wing mem- 

 brane immediately behind the fourth axillary. A downward pull on 

 the lever muscle (fig. 20 A, y8) depresses the lever on its fulcral con- 

 nection (o) with the end of the postphragma, and causes the head {s) 

 to pull backward on the fourth axillary (4AX). The axillary turns 

 on its notal articulation and its outer end pulls on the axillary cord. 

 The wing gives a quick response with a slight backward movement. 

 Slight though this movement of the wing is, the elaborateness of the 

 mechanism that produces it suggests that the movement is one of 

 considerable importance. It may be seen, in fact, that the backward 

 jerk on the extended wing brings the third axillary into a more 

 nearly vertical position in which it becomes quickly responsive to the 

 action of its own muscles. The fourth axillary and its lever in the 

 fore wing of the bee, therefore, appear to be a starting apparatus for 

 the flexor mechanism. 



The flexing of the hind wing is produced entirely by the large third 

 axillary sclerite and its muscle (fig. 21 A, B, ^Ax), since there is 

 no fourth axillary or lever accessory. The axillary region of the 

 hind wing, however, unlike that of the fore wing, is approximately 

 flat when the wing is extended (A). It is probable, therefore, that 

 on relaxation of the extensor muscle the wing automatically turns 

 backward sufficiently to raise the third axillary into a position in 

 which its muscle can become effective. 



