106 NATURAL HISTORY OF WASPS. - 
dissection, to display these suckers on the pulvilli of 
the wasp, which has these parts altogether smaller 
and much less distinct than many of the Diptera. 
Indeed, the bulbed hairs on the wasp’s foot, which 
are meant for suckers to act on smooth surfaces, do 
not seem to play as important a part in her progres- 
sion as the little hooked hairs, which are mixed with 
them, and are as obviously meant for holding to 
rough surfaces. Wasps do not appear at all at ease 
on a polished surface: they cannot walk readily up 
a pane of glass, as their hold is less perfect, and 
their bodies are heavier in proportion to the area of 
their feet than those of flies. They walk much 
better on the rough surface of their own paper nests, 
where their tarsal hooks and the little hooked hairs 
of their pulvilli can be of use, than on the window- 
panes. And they do not seem to take the same quiet 
- monotonous pleasure—happily—as our domestic flies, 
in walking about the windows; it is a scramble up 
and a tumble down, and the sash-bar proves an ob- 
struction only to be surmounted by the aid of their 
wings. 
The wings of the Hymenoptera supply the cha- 
racters by which this large Order of insects is scienti- 
fically distinguished from this others, and is familiarly 
recognized. Some of the most valuable specific dis- 
tinctions between the various subordinate genera are 
also derived from the wings. But, for this purpose 
the fore-wings alone are employed. Whether the 
arrangement of the nervures in the hind-wings is as 
various and as constant for each subdivision as in 
the fore-wings I cannot say. At least, the varieties 
