ANATOMY AND PHYSIOLOGY. Lit 
were made on a humming-bird moth. Butterflies, 
whose up and down flight contrasts strongly with the 
smooth rapid course of the sphinx-moths are entirely 
destitute of it.* 
Other forms of locking-gear are found in the 
Hemiptera. The Notonecta, or boat-fly, which we 
know best as it sculls along on its back, locks its wings 
in flight by means of a little hook which plays along 
the front nervure of the hind wing. This hook springs 
from the under surface of the fore-wing, at the point 
of junction between the clavus and the membrane of 
the elytron. And the same form of hook is found in 
the tropical Belostoma, one of the Nepide, an insect 
whose large size adapts it admirably for the examina- 
tion of the organs of flight. In the British represen- 
tative of the Nepidee, our water-scorpion, the hook is 
made by the edge of the clavus bemg turned down. 
The outer half of this edge hooks into the hind wing 
in flight, while the imner half locks the elytron, in 
repose, to the edge of the thorax. Unless we bend 
the thorax, and so loosen the catch on its posterior 
edge, just as the insect would do, in preparing for 
flight, by the action of the muscles, it requires a 
great deal of force to spread the wings of the larger 
species. 
In the locking-gear as displayed in these different 
instances, and probably many other similar ones 
might be found on more extended examination, it is 
to be observed that the wings are not merely hooked 
together, but that provision is made to keep them 
parallel and. in contact during motion. The connec- 
* See Westwood, ‘ Modern Classification,’ Vol. II, p. 317. 
+ See references, ‘ Cyc. Anat. Phys.’ II, p. 931. 
