It was a long time before I found out what kind of creature the caterpillars stored by Spinipes would have turned into if they had not been caught. I thought that it would have been a small moth, but I was quite wrong. At different times I took several caterpillars away from the tubes, and tried to bring them up, but it was of no use, for they all died because they could not eat. One day, however, I happened to be sweeping with a butterfly-net in a field of lucerne--it is great fun sweeping, and you should try it, for you never know what you may get next--and I swept up what I knew at once was the self-same little green caterpillar that Spinipes stocked her larder with. She _always_ brought the same kind. Well, I got a good many of them by sweeping in the lucerne, and brought them up carefully, and, in due time, they spun little open-work cocoons on the lucerne leaves which I fed them with, and at last turned into small, brown, long-nosed beetles. I need not trouble you with the Latin names of these beetles, but I may tell you that they are a kind of weevil which is very common and very destructive to clover and plants of that kind. So, if we consider that every Mother Spinipes lays eight or nine eggs, and stocks eight or nine burrows each with about thirty destructive little caterpillars, we must allow that she is a very useful little wasp. [Illustration: This is a large picture of Crabro, about twice as big as she really is] But I am not sure that she is more useful to man than the other little wasp I have to tell of, the Crabro. I found out her usefulness quite by chance, and I expect you will like to hear how. To begin with, I must tell you that all the "Digger" Wasps, as some people call them, Spinipes and the Crabros and several other kinds, store their burrows with insect food for their grubs to feed on. [Illustration: This is Crabro looking out of her hole. The front of her face is covered with bright silver hair, so fine that it looks like a silver plate. The picture is twice her real size] [Illustration: This is how the cocoon looked when I had taken the sawdust away. The plug of sawdust above it leads into the round hole in the wood] But each one has her own particular idea as to what is the _best_ food. One will use nothing but little spiders, another nothing but little flies, another, like Spinipes, nothing but little beetle grubs. And the queer part is that they seldom seem to make any mistake as to the kind of food they want. It will be _one_ kind of spider, and _one_ kind of fly, and _one_ kind of beetle-grub. If there are ever more than one kind, they are always very near relations, and, I suppose, taste very much alike. [Illustration: At the bottom of the picture you will see one of Crabro's stores of blue-bottles, and if you look carefully you will see one of the fly's wings stretching out of it]