NO. 2 RECOGNITION AMONG INSECTS — McINDOO ' 55 



Stretch, Grote and Weed (1883) report having seen these append- 

 ages in the same species. Weed also saw them in Pyrrharctia isabella 

 and pronounces them scent-producing organs. 



Smith (1886) also describes these appendages of Lcucarctia acrccc. 

 They project from a narrow opening between the seventh and eighth 

 sterna, and when not protruded they form two invaginated sacs. 

 They are lined with hairs and are united at the base where they are 

 attached to the integument. When protruded the hairs are on the 

 outside of the evaginated sacs. In Pyrrharctia isabella these organs 

 are four snow-white tufts of hair and in both species an intense odor, 

 somewhat like that of laudanum, is emitted when the sacs are 

 evaginated. 



Freiling (1909) asserts that the abdominal scent-producing organ 

 in the female of Taumatopoca pinivora is a large paired tuft of hair 

 on both sides and above the anus. In the female of Stilpnotia salicis 

 this organ is also a paired scent tuft. In the female of Orgyia antiqua 

 it is a scent groove between the eighth and ninth segmfents just above 

 the anus ; here the articular chitin is very thin and it is probably 

 an elastic membrane. Under a high magnification he saw a small 

 quantity of secretion on this membrane. The gland cells are modified 

 hypodermal cells and they lie in groups like several bunches of grapes 

 with their stems attached to a common base. The interior of each 

 bunch is greatly vacuolated and a string of vacuoles extends into each 

 cell. He thinks that the secretion passes from the individual cells 

 through the center of the bunch to the thin membrane where it passes 

 to the outside by infiltration, although he saw no pores in this 

 chitinous membrane. This organ in the female of Bomhyx mori con- 

 sists of the " Sacculi laterales," so called by Techomirow, although 

 he did not understand their function. Freiling considers these the 

 most complete and most highly developed scent-producing organ 

 found in any female lepidopteron. This organ is a pair of invagi- 

 nated and greatly folded sacs ; each sac lies on either side of the abdo- 

 men, and both of them unite and open to the exterior by a long groove 

 between the eighth and ninth segments. The layer facing the lumen 

 of the invaginated sac is a thin and soft chitinous membrane, and it is 

 thickly studded with small prickles. The layer of the sac facing the 

 body cavity of the abdomen is composed of a one-celled layer of uni- 

 cellular glands which are greatly vacuolated. He thinks that the 

 secretion from the glands infiltrates through the thin chitin to the 

 exterior. These sacs are evaginated by blood pressure and are 

 retracted by muscles. He proved experimentally that the females 



