112 UNITED STATES NATIONAL MUSEUM BULLETIN 276 



hindwings crossed beneath (sometimes faintly) by a single whitish line. 

 Epiphysis small (fig. 78), usually about length of second segment of 

 fore tarsus, but rarely a little longer. 



MALE TERMINALIA. — Posterior edge of seventh sternite slightly 

 scalloped, usually with a definite median notch (fig. 60). Genitalia 

 (fig. 31) large compared with other species of the genus (figs. 32-36). 

 Eighth sternite (fig. 40) very large, the "arms" extending well past the 

 parameres (fig. 31), and total length much greater than basal width. 

 Accessory claspers as in figure 1 5. 



ADULT FEMALES (females in figs. 312-320, 208).— Same color 

 pattern as the males, but often somewhat lighter, and more easily 

 confused with females of other species than males. 



FEMALE TERMINALIA.— Genital plate (fig. 90) heavily sclero- 

 tized, variable in shape, but almost always longer than wide, and 

 somewhat heart-shaped, with a deep depression on each side of a 

 median ridge which bears the ostium near the anterior edge. Ovi- 

 positor lobes as in figures 88 and 89. They are quite similar to those of 

 M. californicum and M. incurvum (figs. 91-103), but these two species 

 never have a heavily sclerotized genital plate with the ostium at the 

 anterior edge. 



ADULT DIAGNOSIS.— Both males and females can be identified 

 usually by the nearly white lines on a chocolate-brown ground color. 

 In doubtful cases, positive identification of males can be made by the 

 genitalia which are much larger in absolute size (compare fig. 3 1 with 

 figs. 32-36, and fig. 40 with figs. 37-39 and 41-54). Positive identifi- 

 cation of females can be made by the heavily sclerotized genital plate 

 in combination with the anterior position of the ostium (fig. 90). No 

 other North American species has the ostium at the anterior edge of 

 the genital plate. 



Distribution (fig. 2) is also helpful in identification. The only species 

 or subspecies recorded from within the range of americanum which 

 could be confused with it are M. californicum pluviale and M. californicum 

 lutescens. The male genitalia of these two subspecies, however, are 

 smaller and distinctly different in size. The total length of the eighth 

 sternite (fig. 40) is almost always distinctly greater than the length of 

 the foretibia in americanum, and it is almost always distinctly less than 

 the length of the foretibia in lutescens (figs. 49 and 50) and pluviale 

 (figs. 47 and 48). In addition, the arc of curvature of the "arms" of the 

 eighth sternite near the points is greater for lutescens and pluviale (figs. 

 47-50) than it is for americanum (fig. 40) where there is practically no 

 arc. 



MATURE LARVAE (figs. 350 and 351).— Head black, covered 

 with numerous fine, blackish setae. Body with an apparently continuous, 



