386 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
sockets strongly upraised and as a rule extending backward more 
or less as longitudinal ridges defining laterally a median depressed 
area; antennae usually long and slender, as a rule much longer 
than, or as long as, the head and thorax together, not or scarcely 
thickened before the apex, and composed of nine segments, the 
third of which is longer than the fourth; wings with two radial 
and four cubital cells, the second and third of the latter each 
receiving a recurrent vein; the basal vein meets the subcostal 
considerably before or basal to the point of origin of the cubital 
and is parallel with the first recurrent ; lanceolate cell divided by a 
short vertical cross-vein. 
Geographical Distribution. 
Tenthredella is almost entirely a Nearctic and Palearctic genus, 
a few species being reported from the northern part of the Orien- 
tal region. Dalle Torre (1894) lists one species from the Ethi- 
opian region (Senegal, Africa), but as Konow (1905) does not list 
it, it probably does not belong to this genus. Another is listed 
from the Neotropical region (Venezuela), but it is probably 
not a Tenthredella. No representatives of this genus, as far 
as I know, have been reported from the Australian region. 
The genus is represented in all the zones of North America 
above Mexico, but appears to be rather rare in the Arctic zone. 
The farthest north that a specimen has thus far been taken seems 
to be Lat. 65° [leucostoma (W. F. Kirby) ]. 
The greatest recorded altitude in North America at which a 
specimen has been taken is approximately 11,000 feet, a male 
varifrons (Rohwer) having been taken on the top of Las Vegas 
Range, New Mexico, by Cockerell (Can. Ent., vol. 41, p. Ill, 
1909). In New England the greatest altitude for which I have a 
record is, roughly, from 6200 to 6293 feet, a number of specimens 
of eximia (Norton) and secunda (MacGillivray) having been 
taken near the summit of Mt. Washington, New Hampshire, by 
Mr. George Dimmock. 
Habits. 
The adult Tenthredella, like the Hymenoptera in general, 
delights largely in a bright-sunshiny, warm, and quiet atmosphere. 
The best localities for collecting seem to be in open places along 
