8 PEOCEEDINGS OF THE NATIONAL MUSEUM vol.76 



a peculiar type of dimpled punctures. Patches of dense, minute 

 punctures on the cmierior aspect and the presence and constitution of 

 the preapical hand of punctures just before the apex of the tergite 

 are of value in the females. The triangular first sternite may be 

 coarsely punctate, densely and minutely punctate, or impunctate. It 

 has lateral grooves^ (pi. 4, fig. 31), which are anterior prolonga- 

 tions of the usual posterior transverse fossa. The fossa is frequently 

 crossed by many transverse ridges or crenulae and is then termed 

 crenuiate. The grooves vary in length from less than one-fourth 

 to three-fourths the length of the sternite, though this character 

 should not be too rigidly applied. Just anterior to the constricted 

 portion of the first sternite there is a shield-shaped sternal sclerite 

 termed the escutcheon (pi. 4, fig. 31.) 



The tergites of the intermediate abdominal segments offer diagnos- 

 tic characters in the form of variations in the density and distribu- 

 tion of punctures, the presence or absence of dense, erect, brown pile, 

 of marginal grooves, of vestigial rows of minute punctures (pi. 4, 

 fig. 30), and of apical rows of highly specialized hairs. The impunc- 

 tate apex varies in width, and is measured in terms of the width of 

 the nearest and largest dorsal primary punctures, without considering 

 the thin, membraneous extension of the apex, which is present in 

 many specimens. 



The sternites appear to have few useful characters among the fe- 

 males, though in the Mcarinata group the presence of well differen- 

 tiated apical rows of hairs is quite constant and conspicuous. In the 

 Asiatic males, nearly all species have the minute lateral denticle on 

 the fifth sternite (pi. 4, fig. 27) which readily differentiates them 

 from most of the eastern North American species, in which this char- 

 acter is absent. In some Asiatic males a similar process is developed 

 on the fourth sternite, with possible traces on the segments anterior 

 to the fourth, and in other species a conspicuous orifice is present 

 under the denticle of the fifth sternite. 



The hypopygivmv of the female is usually very uniform, but in two 

 species it possesses diagnostic characters in the form of a narrow, 

 median, hnpunctate lin& (pi. 1, fig. 2). The impunctate line, which 

 is uniformly present in males, has some useful diagnostic characters 

 in its contour and in the nature of the tufts of hair bordering it. 



The pygidiuni of the male is of little value for determinations, 

 but in the female (fig. 1, pyg) it offers a number of highly valu- 

 able specific characters. In most species the punctures are confined 

 to the upper three-fifths, but in some they extend nearly to the tip. 

 In a few species it is entirely and deeply rugose. The apical half 

 may be smooth and highly polished, shagreened, or covered with 

 shallow wrinkles quite different from the rugae mentioned above. 



