THE OLFACTORY ORGANS OF DIPTERA 463 
Disposition of pores in other species 
In making a comparative study of the disposition of the ol- 
factory pores in Diptera, 47 species, belonging to 38 genera and 
representing 21 families, were used. In most cases only one 
specimen of each species was employed, and whenever a portion 
of an appendage or an entire appendage was missing or was 
badly mutilated in being prepared for study, the supposed number 
Fig. 3 Right halter of Musca domestica o’, showing location of scalpel pores 
(nos. 14 and 18), basal pores (no. 15), Hicks’ pores (nos. 16 and 17) and the unde- 
termined type (f). The upper drawing represents the dorsal surface and the 
lower one the ventral surface. The upper margin of each drawing represents 
the anterior surface and the lower margin the posterior surface. F, one of the 
folds caused during preparation of halter. > 100. 
of pores on this portion or entire appendage was regarded the 
same as the number found on the corresponding portion or entire 
appendage on the opposite side of the body. Since the pores on 
only one specimen for each species were counted, the total 
number of pores recorded cannot be a fair average. Besides 
this error, there is also another small probable error for each 
species, because a few of the pores were probably overlooked, 
and often, as on the tibiae, it was impossible to distinguish the 
