38 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 68 



B. Scent-Producing Organs of Other Insects 



A complete review of the literature pertaining to the scent- 

 producing organs of insects has never been presented. Packard 

 (1895, 1903) gives a fair review of this literature up to 1898, and 

 Deegener (1912) briefly discusses the most important papers on this 

 subject appearing between 1898 and 1912, but still the review is far 

 from being complete. It is hoped that a good review of the work 

 already done on this subject will aid and encourage future investi- 

 gators who care to continue work along this line. 



Deegener (1912), briefly reviewing the literature concerning the 

 scent-producing organs of insects, divides them into the three fol- 

 lowing divisions: (i) Stink glands are found in Forficulidae, 

 Orthoptera, Hemiptera, Neuroptera, Lepidoptera, and Coleoptera, 

 and reflex bleeding occurs in Coleoptera, Orthoptera, and Hymenop- 

 tera ; (2) scent glands are found in Lepidoptera in general, and in 

 other insects as Trichoptera, Coleoptera, and Apis; and (3) defense 

 glands are separated from the stink glands only with difficulty. 



Packard has divided these organs into repugnatorial and alluring 

 organs, and a third class including those for recognition only might 

 also be added. Since it is usually impossible to determine whether 

 such organs are used primarily for defense, to allure, or for recog- 

 nition, the present writer has called all of them scent-producing, 

 for in perhaps most cases it is the odors produced that renders them 

 of primary value ; and he has not attempted any classification other 

 than to divide them on the basis of their distribution, which is a con- 

 venient method for description. This review deals only with the 

 literature pertaining to the scent-producing organs of imago insects, 

 and does not include those papers dealing with these organs in larvae. 



I. UNICELLULAR GLANDS WIDELY DISTRIBUTED OVER THE BODY SUR- 

 FACE OF BEETLES, ETC., AS SCENT-PRODUCING ORGANS 



Aube (1837) observed that a fetid and colorless fluid oozes from 

 the surface of the elytra and thorax of beetles. This secretion is 

 produced only when the insect is irritated and a moment after the 

 irritation the insect is covered with many small drops of the liquid. 



Burnett (1854) asserts that in some beetles the secretion is 

 emitted from all parts of the body surface. In bugs the liquid is 

 secreted by a single, yellow or red pyriform gland situated in the 

 center of the metathorax, and opens between the posterior legs. In 

 Formicidse there is an anal gland which ejects a caustic and acrid 



