40 
THORAX, LEGS, AND WINGS, 
being the costal, then the sub-costal, median, and sub- 
median cells, and lastly the internal or anal cell. 
Upon expansion of the wings in flight, the bee has 
the power of making the posterior wing, b, cling to the 
anterior, a, and this gives to the thus consolidated con- 
bination of the two a greater surface and force in 
beating the air to accelerate its progress and carry its 
body. 
The outer margin of the posterior wing (b) is fur- 
nished with a series of booklets {b) curved in an oblique 
direction similar to a corkscrew. The points are blunt, 
and the hooks, of which there are about twenty-three 
(sometimes less), decrease in size towards the end of 
the wing. On the anterior wing at a, corresponding 
to the position of the hooks, the membrane, which is 
here thicker, is folded under and forms a sort of 
trough. The trough and hooks are seen enlarged at 
c. When preparing for flight and the anterior wing is 
brought forward, this trough catches the hooks, which 
are turned up, and the wings are united, as seen at d, 
which is a section through trough and hooks on a 
larger scale. The insect has control over the opera- 
tion of these booklets, for on settling the wings are 
often seen raised perpendicularly over the back of the 
insect. Both wings are slightly convex on the outside. 
Professor Marey (107) has experimented on the flight 
of insects, and has carefully described the movements 
and position of the wings in their progress backwards 
and forwards through the air, although he disagrees in 
some respects with Pettigrew (126) and Amans (i). 
We do not intend to enter into the controversy, as 
