The wing joints act like springs.
The grasshopper does not have to think about shutting up its wings.
John says it has a spring in its wing covers too.
Open the wing cover.
There, it locks itself, as it were, and stays open without any effort on the part of the grasshopper.
You see the grasshopper wants its wing covers to stay open and out of the way of the inner wings when it flies.
So it just opens them, and there they are.
It moves the inner wings very fast indeed when it is flying. It would not do at all for them to be fastened open.
If it did not move them, it could not fly. The wings fairly whirr, they go so fast. They beat against the air, and thus the grasshopper is pushed along through the air.