202 Wisconsin Academy of Sciences, Arts , and Letters. 
each other and thus become permanently attached; this attach¬ 
ment, noticeable at first at the free ends only, soon extends to 
the base of the bristles, which thus become united throughout 
their entire length, forming the large compound frenulum of the 
male moth. As far as can be noticed, the secretion which forms 
the bristles is also used to cement them together. 
An examination of the frenulum of a mature moth under the 
microscope will at once disclose its compound structure, the 
wall and lumen of each bristle being clearly seen. The number 
of these bristles is not easily determined. Sections were made 
both of the frenulum of the mature moth and of that of the moth 
just before leaving the pupal case and before the cuticular cov¬ 
ering had hardened. Even with these sections it was difficult 
to determine the exact number of bristles, but we are led to 
believe that the frenulum of the male wax moth contains from 
twelve to sixteen separate bristles. 
Female moth. The frenulum of the female begins its develop¬ 
ment at a corresponding stage to that at which it appears in the 
male moth. Instead of several enlarged hypodermal cells there 
are only three present; they and their nuclei soon become much 
larger than the trichogens of the male. One can thus readily 
determine the sex of a pupal moth by an examination of the 
frenular area of the hind wing. The frenulum-forming tricho¬ 
gens in the female have each to produce a much greater amount 
of secretion, and they and their nuclei are correspondingly 
larger. 
Here, as in the male, the trichogens sink below the surface of 
the wing but become separated from each other (fig. 5). The 
bristles are at first at right angles to the margin, but soon bend 
towards the apex of the wing and at all times remain entirely 
distinct from each other. The bristles are borne on the outer 
margin of the frenular lobe, and the base of each becomes envel¬ 
oped by a layer of hypodermal cells (fig. 6). 
It was earlier stated that the number of the bristles forming 
the frenulum in the female wax moth varies but that three to 
each hind wing is the commonest number. Having found many 
mature moths with but two bristles on one of the wings, it was 
decided to examine a number of mature female moths to ascer¬ 
tain the relative number of those bearing three or some other 
number of bristles. The following table shows that there is a 
