The expedition has its dangers. The little Spiders may be brushed off by a blade of grass. What becomes of them when they have a fall? Does the mother give them a thought? Does she help them to regain their place on her back? Not at all. The affection of a Spider’s heart, divided among some hundreds, can spare but a very feeble portion to each. The Tarantula hardly troubles, whether one youngster fall from his place, or six, or all of them. She waits quietly for the victims of the mishap to get out of their own difficulty, which they do for that matter, and very nimbly.
I sweep the whole family from the back of one of my boarders with a hair-pencil. Not a sign of emotion, not an attempt at search on the part of the mother. After trotting about a little on the sand, the dislodged youngsters find, these here, those there, one or another of the mother’s legs, spread wide in a circle. By means of these climbing-poles they swarm to the top, and soon the group on the mother’s back resumes its original form. Not one of the lot is missing. The Tarantula’s sons know their trade as acrobats to perfection: the mother need not trouble her head about their fall.
A MEAL OF SUNSHINE
Does the Tarantula at least feed the youngsters who, for seven months, swarm upon her back? Does she invite them to the party when she has captured a prize? I thought so at first; and I gave special attention to watching the mothers eat. Usually, the prey is devoured out of sight, in the burrow; but sometimes a meal is taken on the threshold, in the open air. Well, I see then that while the mother eats, the youngsters do not budge from their camping ground on her back. Not one quits its place or gives a sign of wishing to slip down and join in the meal. Nor does the mother invite them to come and refresh themselves, or put any left-over food aside for them. She feeds and the others look on, or rather remain indifferent to what is happening. Their perfect quiet during the Tarantula’s feast is a proof that they are not hungry.
Then what do they live upon, during their seven months’ upbringing on the mother’s back? One thinks of their absorbing nourishment from their mother’s skin. We must give up this notion. Never are they seen to put their mouths to it. And the Tarantula, far from being exhausted and shriveling, keeps perfectly well and plump; she even puts on flesh.
Once more, with what do the little ones keep up their strength? We do not like to suggest that they are still living on the food they received in the egg, especially when we consider that they must use the energy drawn from this food to produce silk, a material of the highest importance, of which a plentiful use will be made presently. There must be other powers at play in the tiny animal’s machinery.
We could understand their not needing anything to eat if they did not move; complete quiet is not life. But the young Spiders, although usually quiet on their mother’s back, are at all times ready for exercise and for agile swarming. When they fall from the mother’s baby-carriage, 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; they have to stretch and stiffen their little limbs in order to hang on to their neighbors. As a matter of fact, there is no absolute rest for them.
Now physiology teaches us that not a muscle works without using up energy. The animal is like a machine; it must renew its body, which wears out with movement, and it must have something to make heat, which is turned into action. We can compare it with the locomotive-engine. As the iron horse does its work, it gradually wears out its pistons, its rods, its wheels, its boiler-tubes, all of which have to be made good from time to time. The foundry-man and the blacksmith repair it, supply it with new parts; it is as if they were giving it food to renew itself. But, although it be brand-new, it cannot move until the stoker shovels some coal into its inside and sets fire to it. This coal is like energy-producing food; it makes the engine work.
Things are just the same with the animal. Since nothing is made from nothing, the little new-born animal is made from the food there was in the egg. This is tissue-forming food which increases the body, up to a certain point, and renews it as it wears away. But it must have heat-food, or energy-food, too. Then the animal will walk, run, jump, swim, fly, or move in any one of a thousand manners.