478 N. E. McINDOO 
Structure of pores in other species 
Since the structure of the pores in the house fly has been de- 
seribed in detail, only the more important variations concerning 
the structure of the pores in other Diptera will be mentioned 
and attention will be called to the various figures. 
a. External structure. On the legs of one or two specimens the 
pore walls are diamond-shaped instead of being round and oblong, 
Fig. 32 Portion of base of right halter of Musca domestica, cut across in direc- 
tion of line BB in figure 3, showing halter, scalpel pores (nos. 14 and 18), and@& 
basal pores (no. 15) in perspective and in section. The chordotonal organ (ChO) 
and muscle (7) were copied from Weinland (’90) and were drawn in only their 
approximate positions. 
and the pore apertures in several instances are long, more or less 
slit-shaped, and resemble the slits in the lyriform organs of 
spiders (MecIndoo, ’11); such is particularly true on the tro- 
chanters of Tipula (fig. 33). The pores on the tibiae of Sarco- 
phaga (fig. 34) are very large and striking. The pore wall is 
surrounded by three areas of differently colored chitin; the inner 
one is real light in color; the middle one is a little darker, and 
the outer one, having a soft appearance, is still darker. 
