420 N. E. MCINDOO. 



of the same species from 66i to 785 with 720 as an average. It 

 is thus seen that the females of Harpalus have a few more pores 

 than the males, while the males and females of Leptinotarsa 

 have the same number of pores. 



Structure. 

 In the preceding pages it has been shown that most of the 

 variations in regard to the disposition of the olfactory pores are 

 slight. In the following pages it will be shown whether or not 

 this is true for the structure of these pores. 



(a) External Structure. 



When examined under a low-power lens, the olfactory pores 

 may be easily mistaken for hair sockets from which the hairs 

 have been removed. When more carefully observed under a 

 high-power lens, a striking difference in external form is usually 

 seen, but sometimes it is difficult to distinguish the pores from 

 hair sockets. The pores appear as small bright spots when a 

 strong transmitted light is used. Each bright spot has a dark 

 boundary or pore wall (Plate I., Fig. i, PorW)} Near the 

 center of this boundary is a transparent spot, the pore aperture, 

 which may be round, oblong, slit-shaped, or club-shaped. On 

 the legs the pore apertures may be round (Fig. 2, PorAp), 

 oblong (Fig. 3, PorAp), slit-shaped or club-shaped (Fig. i, 

 PorAp). On the elytra and wings they may be round or oblong 

 (Figs. 4 to 8). The hair sockets (Figs, i and 2, PorWHr) are 

 generally smaller than the olfactory pores and the pores of the 

 hypodermal glands (Figs, i and 2, PorWGl) are easily dis- 

 tinguished from the hair sockets and olfactory pores by their 

 small size. 



{h) Internal Structure. 



All the olfactory pores studied are more or less flask-shaped 

 structures. They are of three general types. In the most 

 common type, as found in Uloma, the mouth of the pore (Figs. 

 9-12, Mo) is flaring and the sense cell (Fig. 12, CS) lies in the 

 lumen of the appendage outside the pore cavity. The chitinous 



1 All figures, except Text-figs, i, 2, and 3 are numbered consecutively on Plates 

 I. and II. 



