178 N. E. McINDOO 



While observing a squealing bee, the saddle-shaped subcosta 

 (fig. 1, Sc) rotated quickly on the head of the radius (R) which 

 also vibrated; the bases of the cubitus (Cu), first and third anal 

 veins (lA and SA), and the membranes (Me) between them 

 likewise vibrated, and the median plate {MP) and tegula were 

 observed to move slightly. When the tegula which covers the 

 axillaries was pulled off, the first, second, and third axillaries 

 (IX, 2X, and 3X) and the membranes (Me) between them were 

 seen to vibrate. 



It was not possible to observe the ventral surface (fig. 2) of 

 the base of the wing on the living bee, but a study of its anatomy 

 shows that this surface is better adapted to produce sounds than 

 is the dorsal surface (fig. 1). Reference to figure 2 shows that 

 there is twice as much membrane capable of being vibrated on 

 this surface as on the other surface, due to the fact that the sub- 

 costa (aSc), head of the radius (E), and median plate {MP) are 

 considerably smaller than they are on the other side. In fact, 

 all the membranes, represented by dots in figure 1, were observed 

 to vibrate, and all of those in figure 2, likewise represented, 

 also probably vibrate. Thus it is evident that the extreme bases 

 on these wings make a good sound-producing organ. 



Figure 1 is partly copied from Snodgrass ('10), but the present 

 writer carefully verified all the sclerites here represented, and 

 then made a careful study of the ventral surface (fig. 2), which 

 the former writer did not illustrate. Relative to the muscles, 

 attached to the axillaries, and to the mechanism producing the 

 wing motion, the reader is referred to Snodgrass' bulletin, page 65. 



In this study the group of olfactory pores on the front wings 

 have been more carefully observed than they were formerly by 

 the writer ('14 a). Instead of three groups, there are four groups 

 of them; the fourth group, now numbered J a in figure 2, was 

 formerly overlooked in superficial observations, but was called 

 no. 2 in figures 19 and 20, page 328. Groups 1, la, and 2 are 

 really located on the head of the radius (fig. 2, fl), and not on the 

 subcosta, and group 3 lies on the other side of the same sclerite 

 (fig. 1), and not on the median plate. 



