82 ENTOMOLOGY 



glands (Fig. 146) ; this fluid in Brachinus, and occasionally 

 in Galerita janus and a few other carabids, volatilizes explo- 

 sively upon contact with the air. When one of these " bom- 

 bardier-beetles " is molested it discharges a puff of vapor, 

 accompanied by a distinct report, reminding one of a minia- 

 ture cannon, and this performance may be repeated several 

 times in rapid succession; the vapor is acid and corrosive, 

 staining the human skin a rust-red color. 

 Individuals of a large South American 

 Brachinus when seized " immediately 

 began to play off their artillery, burning 

 and staining the flesh to such a degree 

 that only a few specimens could be cap- 

 tured with the naked hand, leaving a 

 mark which remained for a considerable 

 time." (Westwood.) 



As malodorous insects, Hemiptera are 

 Osmeterium of Papuio notorious, though not a few hemipte- 



polyxenes, 



rous odors are (apart from their associa- 

 tions) rather agreeable to the human olfactory sense. Com- 

 monly the odor is due to a fluid from a mesothoracic gland or 

 glands, opening between the hind coxae. 



Eversible hypodermal glands of many kinds are common in 

 larvae of Coleoptera and Lepidoptera. The larvae of Melasoma 

 lapponica,, among other Chrysomelidae, evert numerous paired 

 vesicles which emit a peculiar odor. The caterpillars of our 

 Papilio butterflies, upon being irritated, evert from the pro- 

 thorax a yellow Y-shaped osmeterium (Fig. 101) which dif- 

 fuses a characteristic but indescribable odor that is probably 

 repellent. The larva of Cerura everts a curious spraying 

 apparatus from the under side of the neck. 



Alluring Glands. Odors are largely used among insects to 

 attract the opposite sex. The androconia of male butterflies 

 have already been spoken of. Males of Catocala concumbens 

 disseminate an alluring odor from scent tufts on the middle 

 legs. Female saturniid moths (as cecropia and promethea) 



