THE OLFACTORY ORGANS OF DIPTERA 473 
pseudohairs arises between each two rows of pores. Each basal 
group consists of about eight rows of pores which are usually 
smaller than the scalpel pores; the pseudohairs in this group 
are also smaller than those in the scalpel group. The Hicks’ 
pores are never protected by pseudohairs. 
ND SDSS EE 
ISSN WOOL SS ~ 
SSS SOS SSS 
ST ee aN aN eas ee 
SO ad 
yh, 44 
I 
Ns YG 
Figs. 16 and 17 External view of scalpel pores (nos. 14 and 18), basal pores 
(no. 15), Hicks’ pores (nos. 16 and 17), and the undetermined type (f) on base of 
right halter of Musca domestica o (fig. 3). All of the pseudohairs (Hr!) in group 
no. 15 are represented, but only a few of those in groups nos. 14 and 18 are shown, 
the bases of the remainder being represented by black dots. X 500. 
b. Internal structure. As in Lepidoptera, the olfactory pores 
of Diptera may be called dome-shaped structures. All of the 
pores on the legs (fig. 18) and most of those on the wings (fig. 
19) are typical dome-shaped structures, while the remainder on 
the wings (figs. 20 and 21) and all of those on the halteres (figs. 
23 to 27) are modifications of the typical structure. It will be 
noted that the internal structure of each type of pore is identical 
to that of any other type and it is also similar to that of the 
THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 29, NO. 5 
