112 NATURAL HISTORY OF WASPS. 
tion is not effected by a hook and eye, but by a hook 
or hooks sliding on a bar. As the wings move for- 
wards to expand, and to take their position for the 
proper muscles of flight to act upon them, the hooks 
catch of themselves, and they are not put out of gear 
till the wings resume the position of rest. This 
arrangement is constant, but which wing shall 
furnish the hooks, and which the slide-bar or catch, 
depends on the anatomy of the particular family. 
One more point yet remains to be considered in 
the structure of the wings. Still speaking of the 
fore-wing, which in the wasp is essentially the 
stroke-oar, we find that its nervures, as they become 
thicker and stronger on approaching the root of the 
wing are gathered into three ridges, forming a nar- 
row neck. From this neck, just as in our bones, the 
condyles of the jomt take their origin. The form of 
the condyles or articulating surfaces scarcely admits 
of any exact measurement in such a small speck as 
the root of a wasp’s wing presents. The necessities 
of the case, however, show that the form and mode 
of attachment must be such as to allow for a move- 
ment in a horizontal direction—as the wasp stands— 
from the position of repose to that of extreme exten- 
sion. A vertical, or up and down movement, and a 
rotatory, or feathering movement, have also to be 
provided for, in combination with this, in the mode of 
articulation of the wings. The human anatomist 
scarcely needs to be reminded of the resemblance of 
this compound movement to that which is provided 
for so exquisitely in our wrists and elbows, and in each 
case by a different mechanism. As the wasp stands, 
the roots of her wings are very nearly in the same 
