396 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
division which is, in all probability, the line of union of the origi- 
nal ninth and tenth terga. In the male, the ninth segment, 
which is rather short, is often not visible, being wholly retracted. 
The first or basal tergum ("basal plates" and "propodium" of 
systematists) articulates with the meta-postscutellum, and to all 
appearances seems to be a part of the thorax, as it does not articu- 
late with the second tergum behind, and, indeed, some have so 
regarded it. It has no sternal counterpart on the venter (the 
term venter is in this paper restricted to the ventral surface of 
the abdomen) ; the sternum of the second tergum is, therefore, the 
first sternum. It is divided by a median longitudinal cleft into 
similar lateral halves, and is roundly and rather widely emargi- 
nate behind. The lateral portions of the remaining terga are con- 
tinued for a short distance on the venter. A spiracle occurs in 
each tergum, except in the last one in the female. The ninth 
segment in both sexes bears a pair of small, hairy, unsegmented, 
finger-like cerci. There are only six sterna in the female, the 
remainder not existing as such, for they have been modified in 
connection with the ovipositing apparatus. The posterior mar- 
gin of the last or sixth sternum is emarginate, usually narrowly 
and deeply, but sometimes widely and shallowly [grandis (Nor- 
ton), and nigricollis (W. F. Kirby)], and from the middle of this 
emargination there projects backward a small, flat, triangular 
process, the free angle of which projects into the basal portion 
of the sheath of the ovipositor. In the male there are seven 
sterna, and the last one, which is comparatively large, will be 
referred to as the hypopygidium in the descriptions. The two 
rather large processes which protrude more or less from the apical 
end of the abdomen of the male are the claspers, — appendages 
of the sexual organs. The two serrate and laterally ribbed saws 
in the female (PI. 4, figs. 5, 6) are enclosed within a chitinized sheath 
which consists of a broader and apparently heavier basal portion 
and a somewhat longer and more slender apical portion (PI. 4, 
fig. 2) . Each of these portions is composed of two plates, one on 
each side, the plates on the same side articulating. The some- 
what longer and more slender apical portion of the sheath will be 
spoken of as the slender portion of sheath of ovipositor in the 
descriptions. 
The abdomen is clothed with very short and fine, sub-erect to 
