1880.} 381 
distinct, the labrum very slightly roughened, its border slightly 
sinuated between the teeth; labrum of the male with a more or less 
distinct median carina, and very slightly roughened, the apex very 
slightly notched in the middle, but without teeth. Clypeus of 
female with the notch deep and narrow. 
The males of this species often vary in having the tibie and last 
tarsal joint black. The females closely resemble the males. 
Isodontia tibialis. Sphex tibialis Lepel., Hym., 111, 339. 
Labrum of female with a sharp median carina, a straight carin- 
iform tooth on each side of it at the apex, and a slightly curved 
transverse carina just behind them, the border excavated between 
the teeth. Labrum of male roughened and with a distinct median 
carina, and a short carina on each side of it at the tip; anterior bor- 
der rounded. The clypeus of the female with the median notch nar- 
row, and deeper than in philadelphica. 
Saussure states (Novara Hymenoptera, p. 39), that the petiole of 
the female of this species, differing from the male, is short as usual 
in Sphez. Ijudge from this that he has confounded the female of 
Sphex flavipes with the female of J. tibialis. 
Dahlbom’s Sphex pennsylvanica is certainly not the Linnean species 
at present recognized under that name, but appears to be a synonym 
of Isodontia tibialis. Yet, such is the confusion of localities in 
Dahlbom’s work, specimens from the most remote quarters of the 
globe being referred to the same species, that little confidence can 
be placed in a synonymical reference when, as in this case, a species 
is said to occur in Pennsylvania and New Holland. As Dahlbom 
had only one specimen of his species it is probable that his des- 
eription relates to some New Holland species which resembles 
Isodontia tibialis. : 
To Jsodontia belong also the following species: J. nigella (Sphex 
nigella Smith) from China, J. azteca (Sphex azteca Sauss.) from 
Mexico, and J. costipennis (Sphex costipennis Spin.) from South 
America. 
I. azteca differs from the other species, with the possible excep- 
tion of costipennis, in the labrum being entirely smooth and unarmed, 
and in the mandibles being bidentate in both sexes. But the mandi- 
bles are short and the teeth apical as in Jsodontia, and the anterior 
tooth in the ¢ is broadly truncate, and evidently corresponds to two 
of the teeth of J. philadelphica. The notch in the clypeus of the 9 
is broad and slight. The petiole is of equal length in the two sexes, 
