NO. 13 STAPH YLINIDAE BLACK WELDER 79 



one to the other in a single membrane (fig. 27 C, E). This pattern is 

 found on Micropepliis, all the Omaliinae, all the Paederinae, Oxyporus, 

 and Bolitohins. 



Two species have a definitely hexagonal pattern (fig. 27 H). They 

 are Leptochirus and Stenus. In Eumalns, Pseiidopsis, and Osorius 

 (fig. 27 J) the areas are very small and angular in shape and grade 

 into elongate transverse pieces near the edges of the membrane. 



The subfamily Staphylininae is characterized by a pattern of ir- 

 regular-sized areas arranged in longitudinal bands separated by clear 

 membrane (fig. 9F). Xantholinns and Mefoponciis differ somewhat 

 in having the areas strongly angular and frequently triangular or 

 lozenge-shaped. Acylophorus is more or less intermediate between 

 these and the typical form for the subfamily, and Quedius is marked 

 only with longitudinal rows of very small spots. 



Oxytehis and Bledhis have a pattern very similar to that shown in 

 figure 9 H except that the bands run transversely. In Aploderus and 

 Platystethus there is no actual pattern, as the minute dots appear like 

 an even stipple. 



In some the membranes appear perfectly clear even under a fairly 

 high magnification. These include Proteinus, Trigonuriis, Habrocerus, 

 Hypocyptus, Tachyporus, Tachinus, Erchomiis, and all the Aleochari- 

 nae studied. 



Various modifications of form and vestiture are found on the ab- 

 domen, but these are not very constant and are frequently modifica- 

 tions of only one sex. The large posterior lobes on the fifth seg- 

 ment of certain males of Gastrolohium (fig. 27 A) and the circular 

 or crescentic groups of setae and pores on the same species are ex- 

 amples of sexual modifications. These groups of setae (fig. 27 A, x) 

 are called foveae in the literature and consist of a circle or band of 

 setae set in moderate sockets and completely surrounded by a large 

 number of pores which give a very rough appearance to the surface. 



The discal setae of BoUtohius (fig. 27 F) do not have a definite 

 socket but are set into the apex of a U-shaped area marked only by 

 a fine line on the surface. The posterior margins of the intermediate 

 segments of Acylophorus (fig. 27 I) are crenulate with the depressions 

 much deeper on the ectal surface than on the ental. A rather large 

 seta is set at the anterior end of each depression. 



The eighth segment is composed of only a tergite and a sternite. 

 The tergite bears a spiracle similarly to the preceding segments and 

 generally is narrower and rather strongly tapering. The eighth seg- 

 ment is usually considered to be part of the genitalia. In the case of 

 the female it is therefore treated in that connection, but in the males 



