THE GENERAL FEATURES OF WINGS 



61 



margin of the front wings (Fig. 45). These hooks are named the hamuli, 

 and ser^'e to hold the two wings of the same side toegther, thus insuring 

 their action as a unit. 



The frenulum and the frenulum hook. — In most moths there is a strong 

 spinc-hke organ or a bimch of bristk'S borne by the hind wing at the humeral 



2d A+Cu, 



Fig. 44. — Wing of Conops; a e, axillary excision; /, y)osterior 

 lobe of the wing. 



angle (Fig. 46,/) ; this is the frenulum or little bridle. As a mle the frenu- 

 lum of the female consists of several bristles; that of the male, of a single, 

 strong, spine-like organ. In the males of certain moths, where the frenu- 

 lum is highly de\-eloped, there is a membranous fold on the fore wing for 

 receiving the end of the frenulum, and thus more securely fastening the two 

 wings together: this is tha frenulum hook (Fig. 46, / h). 



The jiigttm. — In one family of moths, the Hepialid^e, the posterior lobe 

 of the fore wing is a slender, finger-like organ, which is stiffened by a branch 

 of the third anal vein, and which projects beneath the costal margin of the 

 hind wing. As the greater part of the inner margin of the fore wing over- 

 laps the hind wing, the hind wing is held between the two. This type of 

 posterior lobe of the fore wing is termed the jugum or yoke. Figure 47 

 represents the wings of a hepialid seen 

 from below and shows the manner in 

 which the two wings of one side are 

 yoked together. 



The jugum is behind one of the 

 two principal branches of the third 

 anal vein, which may be designated 

 as vein sdAi, and is supported by the 

 other of these two branches, which may 

 be designated as vein sd^lo (Fig. 48). 



The fibula. — In several groups of insects an organ has been developed 

 that serves to unite the fore and hind wings, but which functions in a way 

 quite different from that of the jugum. Like the jugum it is found at the 



Fig. 45. — Wings of a honey-bee; 

 /;, hamuli. 



