NO. 2 RECOGNITION AMONG INSECTS — McINDOO 6l 



senting the families and subfamilies — Cicindelidse, Carabinae, Har- 

 palinae, Feroniinse, Brachininse, Dytiscidse, Gyrinidse, Staphylinidae, 

 and Silphidse possesses anal glands. Bordas (i899d) says that the 

 collections of gland cells may be oblong, grapelike, or may form a 

 solid layer around the collecting tubes their full length. Each uni- 

 cellular gland has a central nucleus and a vesicle which lies near the 

 inner end of the cell from which runs a secreting tubule to the lumen 

 of the collection of cells. The collecting tubes are usually filamentous 

 and tortuous ; the reservoir is ovoid, oblong, or kidney-shaped, and 

 the efferent canal may be long or short. 



Dierckx (i899a-e), whose descriptions and drawings of the anal 

 glands are the most comprehensive of all the researches pertaining 

 to these particular structures, calls them the pygidial glands, be- 

 cause their external openings are a pair of apertures on the pygidium 

 or the last abdominal segment. He used many species of Carabidse 

 and Dytiscidas. Each unicellular gland possesses besides a nucleus, a 

 spherical, cylindrical, pyriform-shaped, or multilobed, radial vesicle 

 which communicates with the lumen of the collection of cells by a 

 filamentous, intravesicular tubule. Near the external opening of the 

 efferent canal he discovered a new gland which he calls the " glande 

 annexe." This structure is also composed of unicellular glands with 

 magnificent radial vesicles. These cells are arranged around the 

 efferent canal into which the secreting tubules empty just at the exit. 

 The secretion of the anal gland is colorless, has a faint odor, and 

 is very volatile. In.Dytiscidae the pygidial gland is double. Each 

 half consists of a long intestinelike collecting tube which is sur- 

 rounded by the unicellular glands, of an ovoid reservoir with feeble 

 muscles, and of a short and tortuous efferent canal leading to the 

 exterior. Each secreting cell has besides a large nucleus, from one 

 to four vesicles which lie in a group. The secretion has an agreeable 

 odor and judging from the anatomy of the reservoir a quick dis- 

 charge is impossible, nevertheless an explosion brought about by this 

 gland never occurs. In Dytisciis the defensive apparatus is the rectal 

 pouch greatly enlarged by water charged with gas. When disturbed, 

 the insect empties its rectal pouch whereby the excremential sub- 

 stances are blown against the enemy. He thinks that the anal glands 

 of Dytiscidae are to facilitate respiration. 



Dierckx (i899f) asserts that the pygidial gland in Stophylinus 

 ccesareus is paired. It seems to be a pair of invaginated sacs which 

 are evaginated by blood pressure and retracted by muscles. The gland 

 cells lie in the walls of the sacs and a secretins: tubule runs from a 



