There must be other powers at play in the tiny animal's machinery.
Total abstinence from food could be understood, if it were accompanied by inertia: immobility is not life.

But the young Lycosae, though usually quiet on their mother's back, are at all times ready for exercise and for agile swarming.

When they fall from the maternal perambulator, they briskly pick themselves up, briskly scramble up a leg and make their way to the top.

It is a splendidly nimble and spirited performance.

Besides, once seated, they have to keep a firm balance in the mass; they have to stretch and stiffen their little limbs in order to hang on to their neighbours.