80 



FAMILY IT. OARAP.TD.^i;. 



XIX. Taciivs Sr-liiuiiii. ISliO. ((h-., "swift.") 



Very siiuill l)l;ick oi- hrownisli spci-ics having' the characters of 

 the tribe Bciiihidilni. Front tibia' oblifjiiely truncate at apex; 

 elytra glabrous, either striate or wholly without stria, except 

 that at sutui'e, which is recuiwed at apex. They occur for the most 

 ])art in damp ])laces, beneath the l)ark of partly decayed logs and 

 stumps; also in moss and ant hills and beneath chunks on mud 

 fiats. When uncovered they run very i-apidly, wdience the generic 

 name. About 45 species are known from the United States; of 

 these 15 have been taken in Indiana. 



The only paper treating of the genus is by: 



Hayinn-d.—'' A Study of the .Spe;-ies of Tachys of Boreal Amer- 

 ica," /» Trans. Amer. Ent. Soc, XXVI, 1899, 191-238. 



Foi- convenience Ilayward divided the genus into nine group.s, 

 his ])iimai'y division Ix^ng based u|)oii the pi'esence oi- absence of 

 punctures on I he mentuni. Of this character he says: "The 

 mentum varies in the different species being more or less emargi- 

 nate in fi'ont, with a tooth of var-ying i)rominence at the bottom of 

 the emargination. In rather more than half of the United States 

 species there may lie observed, behind the tooth, two large fora- 

 mcniform punctures which are entirely al)sent in the other group. 

 These are not difficult to detect, even with a hand lens, and as soon 

 as recognized, their presence or absence can be readily determined, 

 .even in tlie smallest forms." Since only one-third of the specie:-! 

 treated by Ilayward occur in Indiana, they will be separated into 

 but two groups, and this is dom^ only to lessen the length of the 

 keys to species. 



FiK. ^-. n. rncntiini of 7'. rirax: b. mentum (if T. proximus: c. tlurux of 7'. iniuniu: r), thorax of T. iri] unda'.us. 



(After Havward.) 



Ki:V ID CHOI 1>S OK TNDIAXA TACHYS. 



(/. Mciittiiii willHiiit liii'tic iHiiicttircs lit'liiiid the iiicdinii lootli ( Fi.t,'. .'>!', a) ; 

 iu;ir,Lcin:il stfin ol' elytra iiitei-nipl<Ml <ir less dee]* at middle. 



Gronp .1. 



(I'l. Meutiun willi Uvd lar.m' rdraiiieiiirefiii iniiiriiii-cs lieliiiid the tooth. 



(Figr. 52, h.) Group B. 



