'j6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 94 



situation is frequently very different on different legs of the same 

 specimen, but the one from the same thoracic segment of different 

 species can be compared. 



The present subfamily classification of the Staphylinidae is based 

 largely on the shape of the posterior coxae. These segments are 

 classified as globose, conical, triangular, or transverse, and a distinc- 

 tion is often attempted between coxae that attain the pleural pieces of 

 the metasternum and those that do not. 



In all the species studied, and indeed almost necessarily so from a 

 functional viewpoint, the posterior coxae have articulations in two 

 places. Morphologically the more important of these is the pleural 

 articulation which is situated at the lateral extremity of the coxa and 

 at the posterior end of the metathoracic pleurites. This is the most 

 fundamental point in the coxal area and the articulation is probably 

 never lost. The coxa has also a second articulation with the sternum, 

 usually near the midline. Frequently the lateral parts of the coxa are 

 covered by the sternum and are more or less invisible from the ex- 

 terior. It is, then, the exposed portion which has given rise to the 

 above classification, but obviously this is not a fundamental separation. 



The differences between coxae that are " small and globose " (fig. 

 26 G), those that are conical (fig. 26 F), those that are triangular 

 (fig. 26 K), and those that are transverse (fig. 26 C, D, H) are mat- 

 ters of degree and form a continuous series. It should be possible 

 to find a more consistent and fundamental character to express the 

 apparent differences. 



There seem to be three distinct types of coxal structure. In many 

 species the coxa is conical or triangular without expansions beyond 

 the lines connecting the three articulations. In others the side of the 

 coxa is expanded laterally and caudally into a plate which lies under- 

 neath the femur and below (dorsad) the level of the sternum. In 

 the third group there is an upper lamella of the coxa which is expanded 

 laterally and posteriorly into a plate which is nearly at the level of 

 the sternum and completely covers the lower portion of the coxa. 

 These three are the only morphological types recognized. 



The following species belong to the first group, having the coxa not 

 expanded laterally and caudally: Osorlus, Stenus (fig. 26 G), the 

 Paederinae (fig. 26 F), the Staphylininae, and possibly Liparocepha- 

 lus. These are the ones generally said to have the coxae conical or 

 triangular. 



The second group, those having the coxae expanded laterally and 

 caudally into a plate that is partly covered by the femur in repose, 

 frequently also have a slight expansion over the base of the tro- 



