Scent-Organs in some Bombycid Moths. 



By John B. S.mith. 

 At intervals during the past year or two, isolated observations have 

 been made of peculiar filamentary processes protruding from the abdomen 

 of the male of some of our common bombycids, Leucarctia acrcea and 

 Scepsis fidvicollis being the observed species. Not long since, I describ- 

 ed a peculiar abdommal character in the male of Cosmosoma omphale; 

 and the recent capture and examination of specimens ol Leucarctia acrcea 

 has enabled me to add something to the knowledge of the structure in 

 that species. Between the seventh and eighth ventral segments is a 

 narrow opening, entirely invisible in the dried insects, but readily discern- 

 ed on a slight pressure of the abdomen in the fresh specimen. This open- 

 ing extends back about an eighth of an inch, and, on being carefully 

 pried open, shows two closely folded tufts of fine blackish hair. Pressure 

 upon the abdomen will generally force out these tufts, and, if rightly 

 applied, will result in the extension of two orange tentacle like struct- 

 ures, fully half an inch in length, united at the base, and spreading 

 backward and outwardly in a gentle curve. The tufts of hair diminish 

 as the tentacles are extended, the individual hairs occupying small but 

 distinct papillae on the sides, until, when fully extended, they are evenly 

 distributed around them, and no trace of fhe brush-like tuft remains. 

 If the pressure be removed, the tentacles contract, the hairs again form- 

 ing a tuft. 



Specimens of Pyrrharciia 

 isabcUa. when closely examin- 

 ed, showed a similiar abdomi- 

 nal structure; but here there 

 were four tufts extended in- 

 stead uf two, and in color they 

 were snow-white. Properly ap- 

 plied pressure resulted in the 

 inflation, first, of two basal 

 sacs, which, when fully dila- 

 ted, could be compared to 

 y nothing better than the ends of 



I. Leucarctia acraea. 2. Pyrrhaitia Isabella. 4wo thumbs pointing in oppo- 

 site directions, .the hairs of two of the tufts arranged rather densely on 

 the convex outer surface. From the middle of the lower edge of these 

 sacs there extended two tentacles similar to those in acrcea, but not so 

 long; and instead of being evenly clothed with hair, in this species the 



