NO. lO TROPISMS OF LEPIDOPTER^V McINDOO 49 



partially lined with scent hairs at the hases of which lie unicellular 

 glands. In a certain female hutterfly the same organ is present, but 

 there is also a circle of scalelike scent hairs around the anus. In 

 another female butterfly there is a single invaginated sac, similarly 

 located. In the females of the maracuja butterflies, a pair of styled 

 knobs at the posterior end of the abdomen serves as a scent-producing 

 organ. 



The most common type of scent organ in male moths is a tuft of 

 scent hairs on the tibiae of the third pair of legs. Occasionally there 

 are also tufts of hair on the tibiae of the first and second pairs of legs. 

 Another common type in certain male moths is a pair of tufts of 

 scalelike scent hairs at the base of the abdomen. In the males of other 

 moths a pair of invaginated sacs, lined with scent hairs, lies in the 

 ventro-posterior end of the abdomen. In the females of certain moths 

 a paired tuft of scent hairs lies near the anus. The scent-producing 

 organ of the female silkworm moth {Bombyx mori) is the most highly 

 developed of any found in a female lepidopteron. This organ is a 

 pair of invaginated and greatly folded sacs in the posterior end of 

 the abdomen. The female attracts the male by evaginating and turning 

 these sacs inside out, thus fully exposing the inside which is moist 

 with an aromatic substance. In all cases where scent hairs are present, 

 each hair is connected with a unicellular gland. 



The only scent-producing organ found by the writer in codling 

 moths is a pair of invaginated sacs (fig. i6, A) in the ventro-posterior 

 end of the abdomens of males. The mouth of the sac seems to be a 

 long slit along the ventral median line. Muscles (Mii), which nearly 

 surround the sac, apparently change the slit into a wide opening, 

 forcing the 90 scent hairs (//) to the exterior between two abdominal 

 segments. Each hair (fig. 16, B) is long and its base is connected with 

 a single gland cell (Gc) at the anterior end of the sac. In cross section 

 (fig. 16, C) the hairs are round or oblong, are transparent, and have 

 a spongy texture. The outer wall is rough and a pore (/>) can 

 occasionally be seen in it. When greatly magnified the gland cells 

 (fig. 16, D) are large and typical for scent-producing organs. Judg- 

 ing from this structure alone male codling moths attract the females 

 by means of emitting odors from an aromatic substance which passes 

 through pores in the scent hairs to the exterior. 



No one seems to have described a scent-producing organ like the 

 one in the codling moth, but Freiling (23) has described a similar 

 one in a male butterfly (Daiiais scptcntrionalis). In this case the 

 mouths of the paired sacs lie on either side of the anus. Most of the 



