NO. 2 RECOGNITION AMONG INSECTS — McINDOO 5I 



dermal glandular secretion passing- to the exterior through the pores. 

 When irritated the beetles eject small drops of the amber-colored 

 secretion from the f emoro-tibial articulations through the four groups 

 of pores near the articular membrane and those in the membrane. 

 The discharge of the secretion is accomplished by putting the gland 

 cells under a high blood pressure. This is made possible by a 

 muscular contraction in the femur whereby the blood is forced into 

 a specially devised chamber containing the gland cells which belong 

 to the pores in and near the femoro-tibial articulation. 



The gland cells are of two types : those with reservoirs are several 

 times larger than those without reservoirs. The former are widely 

 distributed throughout the entire insect, while the latter is found 

 only under the articular membrane of the femoro-tibial articulation ; 

 in other respects the two types are alike. Each gland cell has an 

 ampulla and a conducting tube which either runs from the ampulla 

 to the reservoir in the chitin or from the ampulla to the surface of 

 the articular membrane. An efferent tube leads from the reservoir 

 to the surface of the chitin. 



The glandular secretion is bitter and has an offensive odor. Its 

 chief purpose is that of protection, but it probably also aids the beetles 

 in recognizing the different individuals and sexes of the same species. 



7. TUFTS OF HAIR ON TIBI.E OF MALE MOTHS AS SCENT-PRODUCING 



ORGANS 



Swinton (1877) observed tufts of hair on the tibiae of the second 

 pair of legs in various genera of Noctuidse; on the tibiae of the third 

 pair of legs in various genera of Geometridae, and on the tibiae and 

 first tarsal joint of the Deltoids. An odor is emitted from each of 

 these tufts of hair. 



Bertkau (i879a-b) found that the tarsi of the third pair of legs 

 in the males of Hepialiis hecta are completely aborted. The tibiae 

 are completely filled with elongated glands which open into pores 

 in the chitin. From each pore arises a long scalelike hair. These 

 hairs form a tuft on the inner side of the tibia and project slightly 

 beyond the distal end of this segment. The same author (1882a) 

 made sections through the tibiae of Hepialus hecta and found large 

 gland cells which are slightly club-shaped and reach entirely across 

 the leg. Their nuclei lie in the broader ends of the cells while the 

 narrower ends extend into the pores and communicate with the club- 

 shaped hairs, which are firmly fastened in the pores by semicircular 

 plates. The secretion of these unicellular glands is a volatile oil 



