Horu.l ^>"4 | Dec. 19, 



grooves and incisures mentioned in the preceding forms. In Harrisii the 

 anterior angles are rather broad and more obtuse than in any of the species 

 described and the incisure beneath them is very feeble. 



Of a totally different type of thorax we must consider saucius and 

 Wl'.edrrl, which require special mention. These have the disc of three 

 parts, a central more depressed portion and the lateral more convex, which 

 may be compared with Eetserius or Plegaderus. The division is best 

 marked in saucius. The region of the anterior angles in this species pre- 

 sents a carious modification, in which the anterior angles appear to be 

 auriculate, but this is really an extension upward and forward of the an- 

 terior margin or collar of the thorax, and corresponds in homology with 

 that portion of the under side of the thorax of the other species which is 

 below the incisure. The true anterior angle will be observed in the figure 

 behind the auriculate process. The hind angles are spiniform, their struc- 

 ture will be observed in the figure. In Wheeleri, the tripartite character is 

 less observable. The anterior angles do not depart much from the normal 

 type, and the incisure beneath is well marked. The hind angles are broad 

 but obtuse, and have a feeble trace of an oblique limiting groove. This 

 species deserves mention as being the only one with the middle coxae 

 absolutely contiguous and the prosternum behind the coxae slightly eleva- 

 ted. 



The legs also vary to an important extent, and will be found described 

 with each species. The tarsi follow the modifications of the legs, and, 

 from being as long as the tibise, are reduced to even less than half that 

 length in Schaumii. As a rule the shorter the tarsi the more compressed 

 do they become, the only exception being in leucostictus, which with short 

 tarsi has the upper side flat, so that the transverse section of a joint would 

 be an isosceles triangle. 



The distribution of the species in accordance with the form of the men- 

 turn is well known. Those with the meutum entire belong from the east- 

 ern base of the Rocky Mountains to the Pacific Coast, there being but one 

 exception, leucostictus, from Maryland. Where the mentum is notched 

 or deeply emarginate, the species belongs to the Atlantic fauna, most of 

 them having a wide range of distribution, except in the case of squamu- 

 losus, which is limited to Georgia and Florida. 



In the accompanying table and descriptions there is very rarely any 

 mention made of the hairs of the surface. These exist to a greater or less 

 extent on all the species, but are very easily removed and are therefore of 

 uncertain value. So also with the spots of whitish exudation which I 

 have observed to a greater or less extent on leucostictus, pilosicollis, angu- 

 laris, Schaumii, Westwoodi, canaliculatus, and castanea. These have all 

 been observed ill ants' nests. 



Mentum plate entire behind. 

 Anterior tarsi with last two joints thickened. 



Clypeus carinate at middle, head with lateral carina' above the eves 

 prolonged backward in obtuse processes planatus Lee. 



