462 N. E. McINDOO 
hence, the pores in nos. 14 and 18 have been called scalpel organs 
because each group lies on a plate shaped like a scalpel. No. 15 
lies on the basal plate, consequently its pores have been called 
basal organs. No. 16 lies on the anterior end of the basal plate, 
while no. 17 on the opposite side of the halter lies on the proximal 
end of the scalpel plate; the pores in these two groups are like 
in structure, and since their structure is like that of those on the 
wings they have been called Hicks’ organs. In the following 
pages it is shown that the scalpel and basal organs are unlike in 
structure and also neither one of these two types is exactly like 
the Hicks’ organs. The isolated pore at f is found on only about 
Fig.2 Portion of left wing of Musca domestica o’, showing location of groups 
nos. 8 to 13 of olfactory pores on propterygium (Pr) and on subcostal vein (Sc) and 
the scattered pores at points marked a toe. The drawing at the left represents 
the dorsal surface and the one at the right the ventral surface. X 20. 
one-half of the halteres of the house fly, and it has been called 
an undetermined type by Weinland. 
Considering the twenty halteres belonging to five males and 
five females, the numbers of pores in the groups are as follows: 
In no. 14 they vary from 74 to 110 with 92 as an average; In no. 
15, from 70 to 96 with 88 as an average; in no. 16, from 10 to 11 
with almost 11 as an average; in no. 17, from 3 to 8 with 7 as an 
average, and in no. 18, from 74 to 110 with 93 as an average. 
