﻿Sept. 1895] Packard. Scent Glands of Insects. 115 



lous aspect to the surface. These lobules are composed of as many as 

 fifty unicellular glands, each of which is composed of four parts: (i) A 

 radiated vesicle, (2) a central sac, giving rise (3) to a fine excretory 

 tube, and (4) a sheath near the origin of the excretory tube. These are 

 all modifications of the cytoplasm of the cell with its reticulum ; the 

 nucleus with its chromosomes is also present, but situated on one side 

 of the central sac. The fine excretory tubules form a bundle passing 

 down into the mouth of each lobule. 



Similar glands, though usually smaller, which have not been care- 

 fully examined, occur in Carabus (Fig. 3) and Cychn/s, which eject from 

 the vent a disagreeable fluid containing butyric acid (Pelouse . The 

 bombardier beetle Brachiniis, with its anal glands, ejects a jet of bluish 

 vapor accompanied with a considerable explosion, which colors the hu- 

 man skin rust red ; it is caustic, smells like nitrous acid and turns blue 

 paper red. Westwood states that individuals of a large South Ameri- 

 can Brachinus on being seized ' ' immediately began to play off their 

 artillery, burning and staining the flesh to such a degree that only a 

 few specimens could be captured with the native hand, leaving a mark 

 which remained for a considerable time." The fluid ejected by an- 

 other species in Tripoli, blackened the fingers of the collector. "It is 

 neither alcaline nor acid, and it is soluble in water and in alcohol " 

 (Kirby and Spence, IV, p. 149). 



Species of other genera {Agoniitn, Pheropsophiis, Galerita, Hel- 

 Jiio, Fai/ssus, OzcBua) are also bombardiers, though less decidedly so 

 than Brachi?ius. A Paussid beetle (^Cerapter!is~) ejects explosively a 

 fluid containing free iodine (Loman), while Staphylini/s, Steiiits, Ocy- 

 pus olens, Lacofi, etc., have similar anal fcetid glands, the liquid beuig 

 more or less corrosive. The secretion of Mortnolyce phyllodes is so cor- 

 rosive that it is said to paralyze the fingers for twenty-four hours after 

 (Cuenot). 



The two pairs of remarkably large soft eversible forked orange yel- 

 low glands of the European genus Malachiiis, are thrust out from the 

 side of the first and the third thoracic segments. They are everted by 

 blood-pressure, and retracted by muscles. The larva of Hydrophilus 

 piceus ejects by the anus a black fcetid fluid. 



Glaus has shown that the larva of Lina popitli and other Chryso- 

 melid?e possess numerous minute eversible glands in each of the warts 

 on the upper surface of the body, each gland containing a whitish re- 

 pellant fluid smelling like the oil of bitter almonds and containing sali- 

 cylic acid derived from its food plant, which issues as pearl-like drops. 



