'IMTH OKorN'i) i!i:i;'rLi:s. 157 



scntclluin distinct. i*Mvti';i not iii;iri;iii('(l ;it l);iso, ;vpex truncate 

 ;ni(l with a nKMuhraiions hoi'tle!": disk not (»r vcvy feebl\' striate 

 arul wntluinf dorsal punctures. Pi'osiortuini not prolon<?od. Tarsi 

 slender, the I'l-ont |)air in the males with tliree joints Feebly di- 

 lated and covered wiHi small scales licneath. The only <j:enus in the 

 I'nited States fauna is — 



LIV. Braciivxi's Web. 1801. (Gr., "short + baek.") 



Small or mediinn sized beetles with hroad abdomen and narrow 

 head and thora.v. Tlie elytra are of a dark blue, blackish- or 

 greenish-blue color, while the head, thorax and legs are reddish- 

 yellow. The generic name refers to the shortness of the elytra. 



They oeenr under logs or stones, usually in damp 

 places. In early spring some of the species are es- 

 pecially abundant and often gregarious in small 

 colonies. When disturbed they emit from a little 

 internal sac near the end of the abdomen a pun- 

 gent, volatile faiid which serves them as a means 

 of defense. This fluid is e.iected with a sound like 

 that of a small popgun, and when it comes in con- 

 tact with the ail- it changes to a gas which appears ng. 86. Brachyn us sty- 

 like steam. For this reason the members of the 

 genus are known as "bombardier beetles." When pursued by 

 some larger insect the bombardier discharges a part of the stored 

 liquid into the face of its enemy, the noise and gas so disconcert- 

 ing the pursuer that the bombardier often has time to escape. 

 Some forms are capable of discharging four or five times in suc- 

 cession. 



But one paper has been issued on the United States species of 

 the genus, viz. : 



LeContc. — "Notes on the species of Brachinus inhabiting the 

 United States," in Proc. Phil. Acad. Nat. Sci., 1862, 523. 



This does not include all of the North American species now 

 known, about 26 in number. The distinguishing characters are so 

 few that no satisfactory table is extanf. Sixteen different forms 

 have been takiMi in Indiana. These were submitted to .Mr. Liebeck. 

 who wrote me concerning them as follows: 



"I assorted your lot of Brachynus and determined them by 

 comparison with the species in the TTorn collection, which is the 

 best I cftuld do. Ttiere the species are arranged in the order in 

 which they are listed bv Ilenshaw. which diff'ers from the old Le- 



