366 TEXT-BOOK OF ENTOMOLOGY 



those (trichogens) which secrete chitinous setae, hairs, and spines, 

 certain setae in some insects being hollow and containing a poison 

 (p. 187) ; others secrete wax, certain ones in Aphids " honey-dew " ; in 

 some cases dermal glands may excrete protective, sticky, or other- 

 wise offensive matters, or may be depuratory, or facilitate the process 

 of moulting. 



There are other minute, unicellular, or compound dermal glands 

 whose function is unknown. 



Dermal glands may be segmentally or serially arranged. Thus 

 Verson has detected a series of one or two pairs of unicellular glands 

 near the stigmata in each thoracic, and the first eight abdominal 

 segments of the silk-worm (B. mori). In the earliest stages of 

 growth of the caterpillar they give out oxalate of lime, and in later 

 stages uric acid. They thus appear to act interchangeably with the 

 urinary tubes, as excretory organs. They do not, however, carry 

 their products directly outwards, but leave them between the hypo- 

 dermis and cuticula, in order to facilitate the sloughing off of the 

 latter in the process of moulting. 



LITERATURE ON THE SECRETORY GLANDS 

 a. General 



Sirodot, S. Recherches sur les se'cre'tions chez les Insectes. (Ann. sc. nat., 



4 Ser., Zool., 1858, x, pp. 141-189, 251-328, 12 Pis.) 

 Gazagnaire, G. Des glandes chez les Insectes. (Compt. rend. Acad. Sc., Paris, 



1886, cii, pp. 1501-1503 ; Annal. Soc. Ent. France, 1886, Bull., pp. 104-106.) 

 Leydig, F. Beitrage zur Anatoinie und Histiologie der Insekten. 1887. 

 Hanow, Karl. Ueber Kerf absonderun gen und ihre Benutzung iin eigenen 



Haushalte. (Programm des Realprogymnasiuins zu Delitzsch fur das 



Schuljahr 1889, xc ; Delitzsch, 1890, pp. 3-22.) 

 Verson, E. Di uua serie di nuovi organi escretori scoperti nel filugello. (Publ. 



R. Stazione Bacologica di Padova, v, 1890, pp. 30. 4 Pis.) 

 Altre cellule glandular! di origine postlarvale. (Ibid., vii, 1892, pp. 16, 



1 PI.) 

 ed E. Bisson. Cellule glandular! ipostigmatiche nel Bombyx mori. 



(Ibid., vi, 1891.) 



Borgert, H. Die Hautdrusen der Tracheaten. Jena, 1891, pp. 80. 

 Batelli, Andrea. Di una particolarita nell' integumento dell' Aphrophorn spu- 



maria. (Monitore Zool. Ital., 1891, Anno ii., pp. 30-32, dermal gland in last 



segment.) 

 Koschewnikow, G. A. On a new compound dermal gland found in the sting of 



the bee. (Journal of the Zoological Section of the Society of the Friends 



of Natural Science. Moscow, ii, Nos. 1, 2, 1892, p. 36. Preliminary notice. 



In Russian.) 

 Willem, V. , et H. Salbe. Le tube ventral et les glandes ce"phaliques des Smin- 



thurus. (Ann. Soc. Ent. Belg., 1897, xli, pp. 130-132.) 

 Henseval, Maurice. Les glandes a essence der Cossus ligniperda. (La Cellule, 



1897, xii, pp. 19-26, 27, 29.) 



