52 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IO3 



The first axillary (fig. 19 E, lAx) is an elongate sclerite with a 

 large anterior head (b) turned laterally on a curved neck, posterior 

 to v^hich is a wide lateral projection (/) and a smaller articular lobe 

 (c) on the mesal margin. The sclerite is attached to the side of the 

 mesonotum in such a manner (J) that its neck rests on the anterior 

 lobe {p) of the notal wing process (F), and its articular lobe is closely 

 hinged to the posterior lobe (q) of the wing process, while the 

 tapering posterior end rests and turns in a concave surface on the 

 lateral margin (r) of the scutal area of the mesonotum (J. set), where 

 normally (D) it is concealed in a pocket of the wing membrane be- 

 neath the fourth axillary (4 Ax). In the natural position of the 

 extended wing (A) the first axillary (lAx) stands almost vertical; 

 in the flattened wing base (D) it is seen that its head abuts against 

 the humeral complex, and the lateral projection underlaps the median 

 plate (in). The first axillary is the anterior hinge plate of the wing. 



The second axillary (fig. 19 E, 2Ax) is a thick sclerite standing 

 vertically in the wing base. Its exposed upper surface (i) appears 

 as a small oval plate (D) lying in the notch between the head and 

 the body of the first axillary. Ventrally the second axillary articulates 

 by an anterior knob (E, B, /) with the wing process of the pleuron, 

 and by a posterior arm (k) is associated with the subalar sclerite (B, 

 Sa) on the upper edge of the pleuron. The second axillary is the 

 pivotal sclerite of the wing base, since it is the only axillary sclerite 

 that articulates with the pleuron and gives the wing a solid support 

 from below. In the bee the second axillary has no direct connection 

 with any of the wing veins, though in most insects it is connected 

 with the base of the radius. 



The third axillary (fig. 19 E, jAx) is an elongate sclerite lying 

 close along the axillary cord (D), with its tapering distal end as- 

 sociated with the enlarged base of the single anal vein of the wing. 

 Proximally the third axillary bears a large lobe (E, /) projecting 

 anterior to its axis, on which are inserted three muscles arising on 

 the mesopleuron (H). The small, flat uppermost muscle (H, /6a) 

 arises in the pocket of the inner wall of the pleuron (fig. 17 B) be- 

 neath the reflected plate (g) ; the other two larger muscles (fig. 19 H, 

 /6b, /6c) arise ventrally on the episternum. The third axillary is 

 the only axillary sclerite of the wing base provided with muscles; it 

 is the effective skeletal element of the wing-flexing mechanism, and 

 may be termed the flexor sclerite. 



The fourth axillary (fig. 19 E, 4AX) is a small, irregularly tri- 

 angular sclerite lying transversely in the posterior angle of the wing 

 base (D), articulated mesally on the lateral margin of the scutal area 



