552 PROCEEDINGS OF THE ACADEMY OF [Aug., 



defence, the fifth type of scent-producing organ is the most highly 

 organized of all five types. For storing the secretion, the ear-wig 

 has two pairs of reservoirs in the third and fourth abdominal terga 

 (Vossler, 1890). Both sexes of walking-sticks have two straight, 

 ribbonlike blind sacs which lie in the thorax (Scudder, 1876). The 

 electric-light bug has two long coecal tubes in the metathorax (Leidy, 

 1847) . In another bug, Pyrrhocoris apterus, the scent-producing organ 

 is quite complicated. It' has a specialized reservoir with a valve to 

 prevent the escape of. the secretion (Mayer, 1874). The male 

 roaches Periplaneta orientalis and P. americana have, besides the scent- 

 producing organ in the articular membrane already mentioned, 

 anal glands which are highly organized (Bordas, 1901). The uni- 

 cellular glands belonging to the anal glands of a beetle, Blaps mortisaga, 

 are very similar in structure to those of the bee (Gilson, 1889). 

 Many species of Carabidse and Dytiscidse have been studied by 

 Dierckx (1899). He finds that all their anal glands are highly 

 organized and that the secretion is produced by many unicellular 

 glands which lie either in the tubes leading to the reservoir or lie a 

 short distance from these tubes. All of the gland cells are quite 

 similar in structure to those of the bee. A highly organized anal 

 gland has also been found in a few ants (Forel, 1878). 



From this brief outline, it is seen that scent-producing organs 

 have already been found in many insects belonging to five orders. 

 There is a wide variation in organization between the lowest type 

 and the highest type. All of those organs belonging to the first 

 four types are used in all probability for alluring purposes and as a 

 means for recognition, while those of the fifth type are perhaps used 

 only as a means of defence. Of the scent-producing organs used for 

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

 organized. 



Literature Cited. 



Bbrlebe, Antonio. 1906-1909. Gli insetti, vol. 1, pp. 535 535 



Bertkau, Ph. 1882 Ueber den Duftapparat von Hepialus Heota L. Arch f 



Naturgesch., Jahrg. 48, Bd. 1, pp. 363-370. ^ii-n.i. 



Bordas L. 1901 Lesglandes defensives ou odorantes des Blattes. Comptes 



Rendus Acad. Sci. Pans, t. 132, pp. 1352-1354. "iui^i^i-a 



Dbegener, Paul. . 1905. Das Duftorgan von Phassus Schamyl Chr. I Anato- 



misch-histologischer Theil. Zeitsoh. f. wiss. Zool., Bd. 78 pp 245-255 

 ^'''I'iS ^''•l ^ n^-r ^*i"'^^ compar^e des glandes pygidiennes chez les Cara- 



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