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 (Cw), first and third anal 
veins (1A and 3A), 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 
(1X, 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 (Sc), head of the radius (R), 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 (14a). Instead of three groups, there are four groups 
of them; the fourth group, now numbered /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, R), 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. 
