There are many Bees who, like the Leaf-cutters, do not make their own dwellings, but use shelters made by the work of others. Many of the Osmia-bees seize the old homes of the Masons; other honey-gatherers use earthworm galleries, snail-shells, dry brambles which have been made into hollow tubes by the mining Bees, and even the homes of the Digger Wasps burrowed in the sand. Among these borrowers are the Cotton-bees, who fill the reeds with cottony satchels, and the Resin-bees, who plug up snail-shells with gum and resin.

There is a reason for such arrangement. The Bees who work hard to make their homes, such as the Mason-bee, who scrapes hard clay and makes a large cement mansion, the Carpenter-bee, who bores dead wood to a depth of nine inches, and the Anthophora, who digs corridors and cells in the banks hardened by the sun, have no time left to spend in furnishing their cells elaborately. On the other hand, the Bees who take possession of ready-made homes, are artists in interior decorations. There is the Leaf-cutting Bee, who makes her leafy baskets with such skill; the Upholsterer-bee, who hangs her cells with poppy-petals, and the Cotton-bee, who makes the most beautiful purses of cotton.

We have only to look at the Cotton-bee’s nests, to realize that the insect who makes these could not be a digger, too. When newly-felted, and not yet sticky with honey, the wadded purse is very elegant, of a dazzling white. No bird’s-nest can compare with it in fineness of material or in gracefulness of form. How, with the little bales of cotton brought up one by one in her mouth, can the Bee manage to mat all together into one material and then to work this into a thimble-shaped wallet? She has no other tools to work with than those owned by the Mason-bees and the Leaf-cutting Bees; namely, her jaws and her feet. Yet what very different results are obtained!

It is hard to see the Cotton-bees in action, since they work inside the reeds when making the nests. However, I will describe the little that I saw. The Bee procures her cotton from many different kinds of plants, such as thistles, mulleins, the woolly sage and everlastings. She uses only the plants that are dead and dry, however, never fresh ones. In this way she avoids mildew, which would make its appearance in her nests in the mass of hairs still filled with sap.

She alights on the plant she wishes to use, scrapes it with her mouth, and then passes the tiny flake to her hind-legs, which hold it pressed against the chest, mixes with it still more down, and makes the whole into a little ball. When this is the size of a pea, it goes back to the mouth, and the insect flies off, with her bale of cotton in her mouth. If we have the patience to wait, we shall see her coming back again and again to the same plant, until her bags are all made.

The Cotton-bee uses different grades of cotton for the different parts of her work. She is like the bird, who furnishes the inside of her nest with wool to make it soft for the little birds, and strengthens the outside with sticks. The Bee makes her cells, the grubs’ nurseries, of the very finest down, the cotton gathered from a thistle; she makes the barrier plug at the entrance of stiff, prickly hairs, such as the coarse bristles scraped from a mullein-leaf.

I do not see her making the cells inside the bramble, but I catch her preparing the plug for the top. With her fore-legs she tears the cotton apart and spreads it out; with her jaws she loosens the hard lumps; with her forehead she presses each new layer of the plug upon the one below. This is a rough task; but probably her general way of working is the same for the finer cells.

Some Cotton-bees after making the plug go even further and fill up the empty space at the end of the bramble with any kind of rubbish that they can find: little pieces of gravel, bits of earth, grains of sawdust, mortar, cypress-catkins, or broken leaves. The pile is a real barricade, and will keep any foe from breaking in.

The honey with which the Cotton-bee whose nest I examined filled the cells was pale-yellow, all of the same kind and only partly liquefied, so that it would not trickle through the cotton bag. On this honey the egg is laid. After a while the grub is hatched and finds its food all ready. It plunges its head in the honey, drinks long draughts, and grows fat. We will leave it there, knowing that after a while it will build a cocoon and turn into a Cotton-bee.

Another interesting Bee who uses a ready-made home is the Resin-bee. In the stone-heaps which have been left from the quarries, we often find the Field-mouse sitting on a grass mattress, nibbling acorns, almonds, olive-stones, apricot-stones, and snail-shells. When he is gone, he has left behind him, under the overhanging stones, a heap of empty shells. Among these, there is always a hope of finding a few plugged up with resin, the nests of this sort of Bee. The Osmia-bees also use snail-shells, but they plug them up with clay.

It is hard to tell the Resin-bees’ nests, because the insect often makes its home at the very inside of the spiral, a long way from the mouth. I hold up a shell to the light. If it is quite transparent, I know that it is empty and I put it back to be used for future nests. If the second whorl is opaque, does not let the light through, the spiral contains something. What? Earth washed in by the rain? Remnants of the dead Snail? That remains to be seen. With a little pocket-trowel I make a wide window in the middle of the final whorl. If I see a gleaming resin floor, with incrustations of gravel, the thing is settled: I have a Resin-bee’s nest.

The Bee picks out the particular whorl of the shell which is the right size for her nest. In large shells, the nest is near the back; in smaller shells, at the very front, where the passage is widest. She always makes a partition of a mosaic formed of bits of gravel set in gum. I did not know at first what this gum was. It is amber-colored, semi-transparent, brittle, soluble in spirits of wine, and burns with a sooty flame and a strong smell of resin. These characteristics told me that the Bee uses the resinous drops that ooze from the trunks of various cone-bearing trees. There are plenty of junipers in the neighborhood, and I think that these form the main part of this Bee’s materials. If there were pines, cypresses, and other cone-bearing trees near, she would probably use those.

After the lid of resin and gravel, the Bee stops up the shell still further with bits of gravel, catkins and needles of the juniper, and other odds and ends, including a few rare little land-shells. This is the secondary barrier, to make the shell still safer for her nest. The Cotton-bee uses the same sort of barrier in the bramble. The Resin-bee uses it only in the larger shells, where there is much vacant space; in the smaller ones, where her nest reaches nearly to the entrance, she does without it.

The cells come next, farther back in the spiral. There are usually only two. The front room, which is the larger, contains a male, which in this kind of Bee is larger than the female; the smaller back room houses a female. It is extraordinary how the mother Bee knows the sex of the egg she is laying. This matter has never been explained to the satisfaction of scientists. The Resin-bee makes a mistake in choosing large shells and not filling them up to the very entrance. The Osmia-bee also makes her nest in snail-shells; she often seizes upon the empty rooms in the Resin-bee’s house and fills them with her mass of cells. She then stops up the entrance with a thick clay stopper. When July comes, this house with the two families of tenants becomes the scene of a tragic conflict. The Resin-bees, in the back rooms, on attaining the adult state, burst their swaddling bands, bore their way through the resin partitions, pass through the gravel barricade and try to release themselves. Alas, the strange family ahead blocks the way! The Osmia inmates are still in the grub stage; they mean to stay in their cells till the next spring. The Resin-bees cannot get out through this second row of clay-stoppered cells; they give up all hope and perish behind the wall of earth. If their mother had only foreseen this danger, the disaster would never have happened; but instinct has failed her for once. Misfortune has not taught the Resin-bees anything through all the generations; and this contradicts the theory of those scientists who say that animals learn through experience.