THE THREAD-LEGGED BUGS. 511 



Family XVIII. PLOIARIID^E Dohrn, 1863, 43. 

 The Thread-legged Bugs. 



Heteroptera of very slender elongate form and variable 

 length having the head either porrect or declivent behind, not 

 pedicillate, usually divided into two lobes by a transverse suture 

 between the eyes ; ocelli absent ; eyes placed on sides of middle 

 of head, usually large and coarsely granulated ; antennae 4- 

 jointed, the first and second joints unusually long; beak short, 

 3-jointed, attached to tip of head, without downward project- 

 ing bristles, the basal joint bent downward ; pronotum variable 

 in form and size ; scutellum small, triangular ; elytra often 

 absent, when present in great part hyaline and of uniform 

 texture throughout ; front legs raptorial, their coxal cavities 

 opening forward and downward and with a minutely striated 

 longitudinal groove between them, the coxae greatly elongated, 

 reaching or surpassing apex of head ; front femora armed 

 beneath with numerous spines or setse; front tibiae strongly 

 retractile, also usually armed beneath ; middle and hind legs 

 filiform, very long and slender. 



As treated by McAfee & Malloch (1925) the family is rep- 

 resented on the American continent by about 160 known 

 species, 44 of which are found in the United States. Of these 

 26 are known from our territory. They occur mostly beneath 

 loose bark, in the bases of tufts of grass, in bunches of dead 

 leaves, or in old barns, dwellings, cellars and outhouses, where 

 they prey upon other insects which happen in their way. Our 

 United States species are distributed among eight genera, 

 seven of which are represented in the eastern states. The prin- 

 cipal literature pertaining to them is by Dohrn, 1860, 1863 ; 

 Stal, 1872, 1874; Champion, 1898; Banks, 1909; Bergroth, 

 1906a, 1922a, 1922b; McAfee & Malloch, 1925. 



KEY TO EASTERN GENERA OF PLOIARIID.T:. 



a. Front tarsi flexible, distinctly 2- or 3-jointed; front trochanters 



unarmed; body of adults winged, the elytra surpassing abdomen; 



front femora spinose from the base; claws of front tarsus two, 



usually equal. 



b. Elytra with two completely enclosed discal cells, the basal one 



triangular (fig. 1) ; 59 pronotum extending backward over mesono- 



tum to bases of wings, always with a deep constriction, some- 



59 The figures cited in keys and descriptions of the family Ploiariida? refer, for 

 the most part, to those on plates V and VI, pages 512 and 528. 



