66 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 68 



In regard to storing the secretion in an ** evaginable " sac, the third 

 type is a httle further advanced than the second type. The sacs 

 are evaginated by blood pressure and retracted by muscles, and the 

 odorous substance may be more or less retained in the invaginated 

 sacs, but when the sacs are evaginated, like the fingers of a glove, 

 all the odor escapes. 



In regard to storing the secretion, the fourth type is more highly 

 organized than any one of the preceding types. The scent-producing 

 organ of the honey-bee belongs to this type, and it is one of the most 

 highly developed organs of its kind. At this place might be mentioned 

 some unicellular glands found in ants. In the petiole of the worker 

 ant of Myrmica rubra, Janet (1898) found an invaginated chamber; 

 at the bottom of the chamber may be seen the exits of the tubes which 

 lead to a bunch of unicellular glands. He also found in the same ant 

 two small groups of unicellular glands beneath the articular mem- 

 brane between the ninth and tenth abdominal terga. These glands are 

 also connected with tubes which run to the exterior. Both of these 

 organs may possibly be scent-producing organs, and may be similar 

 in function to that of the honey-bee. 



Relative to storing and discharging the secretion as a means of 

 defense, the fifth type is the most highly organized of all the five 

 types of scent-producing organs. It is thus seen that there is a wide 

 variation in organization between the lowest type and the highest 

 type. All of those organs belonging to the first fpur types are used 

 in all probability for alluring purposes and as a means of recogni- 

 tion, while those of the fifth type are perhaps used mostly as a 

 means of defense. Of the scent-producing organs used only for 

 recognition, that of the honey-bee is probably the most highly 

 organized. 



ORTHOPTERA 



In the ear-wig, Forficula aiiriciilaris, the scent-producing organ 

 consists of two pairs of lateral, saclike invaginations located in the 

 third and fourth abdominal terga. The walls of these sacs, the 

 reservoirs, are composed of unicellular glands. 



In both sexes of the roach Corydia two pairs of caruncles or 

 evaginated saclike appendages serve as the scent-producing organ. 

 These appendages are located on the pleura of the first and second 

 abdominal segments. Unicellular glands lie in their walls. In the 

 roach Pcriplaneta there appear to be at least three scent-producing 

 organs. The males have anal glands and probably the females (the 

 writers did not determine the sex) have a pair of lateral pouches in 

 the articular membrane between the fifth and sixth abdominal 



