NO. 2 HONEY BEE SNODGRASS 57 



axillary (ydb, /'6c). The contraction of this muscle turns the basalare 

 inward on the supporting pleural lobe, and the movement is trans- 

 mitted to the wing because of the close connection of the basalare 

 with the humeral angle of the wing base. 



The subalare of the mesothorax is a small triangular sclerite (fig. 

 19 I, Sa) but little visible in lateral view (B) beneath the posterior 

 part of the wing. Its broad base is supported on a longer sclerite (I, 

 h), which in turn rests on the inner margin of the inflected dorsal 

 plate of the epimeron (Epm'), and is linked posteriorly with the 

 anterior extremity of the stalk of the postphragma {2Ph). On the 

 upper angle of the subalare is attached the tendon of a long muscle 

 {82), which arises ventrally on the mesothoracic coxa (figs. 17 G, 

 22 C, 82). The subalare is closely associated with the posterior basal 

 process of the second axillary sclerite (fig. 19 B), so that the pull 

 of its muscle is indirectly transmitted to the pivotal sclerite of the 

 wing base. 



The epipleural sclerites of the metathorax have the same relations 

 to the hind wing as do those of the mesothorax to the fore wing. The 

 triangular basalare (fig. 21 B, Ba) sits on a marginal elevation of 

 the metapleuron before the second axillary (C, Ba), and the small 

 subalare (B, Sa) is attached to the concave pleural margin behind 

 the second axillary (C, Sa). A single large basalar muscle (H, loi) 

 arises on a lobe (r) of the ridge in the metapleural area behind the 

 middle leg (fig. 16 H, r), and tapers upward to a strong tendon at- 

 tached mesally on the basalar sclerite (fig. 21 B, H, Ba). The small, 

 inconspicuous subalare (B, Sa) has an elongate apodemal process 

 on which are inserted two muscles, one a long fusiform muscle {10^), 

 corresponding with the subalar muscle of the mesothorax, which 

 arises ventrally on the hind coxa (fig. 24 A, 10^), the other a broad 

 thick muscle (fig. 21 B, C, H, 102) arising on the upper plate of the 

 metapleuron, and apparently represented in the mesothorax by a 

 similar pleural muscle (fig. 17 E, yf,) attached dorsally on the margin 

 of the posterior scutal plate of the mesonotum (fig. 19 F, /^). The 

 subalare is intimately associated with the second axillary of the wing 

 base (fig. 21 B, 2Ax) by a close membranous connection {h) with 

 the posterior basal arm of the latter. 



The mechanism of flight. — To understand the movements of an 

 insect's wings it is necessary to observe first that the wings are sup- 

 ported from below on the second axillary sclerites of their bases, and 

 that these sclerites rest on the upper edges of the pleura, while the 

 flexible attachments of the wings to the notal plates lie a little mesad 

 of the pleural supports. As a consequence a slight depression of the 



