TI. SEXUAL SPOTS OF MALE DANAIS 
619 
In doubtful cases one must not pass over any circumstance, however 
unimportant it may appear, and I therefore mention the fact that in some 
males of D . erippus, otherwise perfect, a very small portion of the wing, 
close to the orifice of the sexual cavity, was entirely denuded of scales, as 
if they had been repeatedly rubbed away by introducing something into 
the slit. Is it not possible that some odoriferous substance may be 
produced in the interior of the sexual spot, and that the hairs of the 
abdominal organs introduced into its cavity may become impregnated with 
this substance ? 
The position and shape of these sexual cavities is such that the extremity 
of the abdomen might easily be applied to them, and as the hairs of the 
abdominal organs unite in the form of a brush, it would not be impossible, 
or even difficult, to introduce them into the depths of the cavity. 
I confess, frankly, that this idea appears to me to be well founded, but 
it is only by a comparative study of the numerous species of Danais that 
we can arrive at a definite solution of this interesting problem. 
