ANATOMY AND PHYSIOLOGY. “ 119 
circumstances, shows how very difficult it is for them 
to keep in the same place. And for the same reason 
that they cannot rise, namely, that so much of the 
force of the blow is lost on the moving air, in what 
is technically called slip. The maxim, that you must 
learn to stand before you try to run, scarcely holds 
good beyond the walls of the nursery. And it has 
no application whatever to the art of flying, any 
more than to walking on stilts or swimming. To — 
stand still is one of the most difficult feats in flight. 
But when the place of the insect is being con- 
stantly changed, when each beat of the wings takes 
them out of the range of the influence of the last 
beat, and places them in a resisting medium, their 
movements are much more easy. Besides, each yard 
of space traversed contributes something of upward 
pressure to the support of the bird or insect lying 
obliquely on it. And, at a high speed, the total 
amount of the upward pressure over a long path, in 
other words, of the support from the air itself, is 
something very considerable. 
The adjustment of the wings is at once the most 
intricate and the most mterestng part of the problem 
of fight. Much of what has been already passed in 
review can be explained on mathematical principles, 
and much we can actually imitate by mechanical 
expedients. But here, in the rapid motions of these 
little organs, observation is taxed in collecting the 
materials for a scientific mduction, imitation quite 
fails us, and it is as much as we can do to interpret 
the results with any assurance of correctness. With 
such reservations I venture on the followmg expla- 
nation of the movements of flight in wasps :— 
