Casey — A Revision of the American Paederini. 219 



Labrum broadly rounded or subtruncate at apex, the teeth two in number, 

 more or less aciculate and always approximate; second joint of the 

 maxillary palpi much shorter than the third; anterior tarsi finely, 

 densely pubescent beneath; prosternum very finely, feebly carinate 

 throughout 2 



Labrum broadly sinuato-emarginate at apex, the emargination having two 

 short obtuse and more widely separated teeth; second palpal joint very 

 much shorter than the third; anterior tarsi not at all dilated, having 

 long coarse hairs beneath; prosternum finely, unevenly and feebly 

 carinate 3 



Labrum quadridentate at apex and generally broadly subtruncate and 

 triemarginate 4 



2 — Head rounded to subtruncate at base, the body rather slender; legs and 

 tarsi slender; sculpture more or less coarse. Palaearctic and Nearctic 

 regions St i liens 



Head broadly sinuate at base, the body very stout; legs and tarsi thick; 

 sculpture very fine and dense. Nearctic regions Pachystilicus 



3 — Body very stout with the head orbicular; third maxillary palpal joint 

 unusually small, subcylindric and bent; sculpture fine and dense, the 

 vestiture very short and stiff; femora and tibiae rather thick, the hind 

 tarsi slender and almost as long as the tibiae. Myrmecophilous. 

 Nearctic regions Megastilicns 



4 — Outer pair of labral teeth as large and conspicuous as the inner; second 

 palpal joint much shorter than the third; anterior tarsi slightly dilated 

 and more densely pubescent beneath; legs slender; sculpture coarse as 

 in Stilicus. Palaearctic regions *Stilicosoma 



Outer pair of labral teeth very minute; anterior tarsi not dilated and 

 usually not densely clothed beneath; sculpture of the integuments 

 always very fine and dense 5 



5 — Prosternum strongly carinate throughout its length 6 



Prosternum not at all carinate except posteriorly near the coxae 7 



6 — Inner pair of labral teeth short and broad, widely separated, each tooth 



deeply bifid and forming two acute denticles; labrum not at all pro- 

 duced in the middle but broadly subtruncate; head rounded at base, 

 the eyes moderate or rather small; second palpal joint but little shorter 

 than the third, moderately elongate; gular sutures as usual; prothorax 

 oblong-parallel, the angles distinct. Nearctic regions Stil icolin a 



Inner pair of labral teeth strong, the labrum elongated in the middle; 

 maxillary palpi very long; mandibles broad; prosternum elongate, the 

 prothorax without the lateral angles of Stilicus. Tropical America. 



*Eustilicus 



7 — Labrum broadly truncate and deeply trisinuate, the median teeth long, 

 simple and aciculate; mandibles broad and strong; maxillary palpi 

 long, the second joint slightly shorter than the third; gular sutures 

 meeting behind the middle; head subtruncate at base, the eyes very 

 small; prothorax obtrapezoidal, the anteriar angles rounded; legs long, 

 the femora somewhat stout. Sonoran region Omostilicns 



The characters of the Mexican and Central American 

 Eustilicus Shp., are taken from the "Biologia; " at first it 



