Now that we know what the provision-jar is like, we must find out what it contains.
The young Pelopæus is fed on Spiders. The food does not lack variety, even in the same nest and the same cell, for any Spider may form a meal, as long as it is not too large for the jar. The Cross Spider, with three crosses of white dots on her back, is the dish that occurs oftenest. I think the reason for this is simply that the Wasp does not go far from home in her hunting-trips, and the Spider with the crosses is the easiest to find.
The Spider, armed with poison-fangs, is a dangerous prey to tackle. When of fair size, she could only be conquered by a greater amount of daring and skill than the Wasp possesses. Moreover, the cells are too small to hold a bulky object. The Wasp, therefore, hunts game of moderate size. If she meets with a kind of Spider that is apt to become plump, she always chooses a young one. But, though all are small, the size of her victims varies enormously, and this variation in size [[80]]leads also to variation in number. One cell will contain a dozen Spiders, while in another there are only five or six.
PELOPÆUS SPIRIFEX
When finished the work is amber-yellow, and rather one of the outer skin of an onion
Another reason for her choice of small Spiders is that she kills them before potting them in her cells. She falls suddenly upon her prey, and carries it off almost without pausing in her flight. The skilful paralysis practised by some insects is unknown to her. This means that when the food is stored it soon decays. Fortunately the Spiders are small enough to be finished at a single meal. If they were large and could only be nibbled here and there, they would decay, and poison the grubs in the nest.
I always find the egg, not on the surface of the heap, but on the first Spider that was stored. There is no exception to this rule. The Wasp places a Spider at the bottom of the cell, lays her egg upon it, and then piles the other Spiders on the top. By this clever plan the grub is obliged to begin on the oldest of the dead Spiders, and then go on to the more recent. It always finds in front of it food that has not had time to decompose.
The egg is always laid on the same part of the Spider, the end containing the head being placed on the plumpest spot. This is very pleasant for the grub, for the moment it is hatched it can begin eating the tenderest and nicest [[81]]food in the store. Not a mouthful is wasted, however, by these economical creatures. When the meal is finished there is practically nothing left of the whole heap of Spiders. This life of gluttony lasts for eight or ten days.
The grub then sets to work to spin its cocoon, a sack of pure, perfectly white silk, extremely delicate. Something more is required to make this sack tough enough to be a protection, so the grub produces from its body a sort of liquid varnish. As soon as it trickles into the meshes of the silk this varnish hardens, and becomes a lacquer of exquisite daintiness. The grub then fixes a hard plug at the base of the cocoon to make all secure.