“The flowers which deck the mountain streams with gold supply her with sugary liquid and pollen.”
When all the cells are finished, the Bee builds a thick cover over the group, to protect her grub-babies from damp, heat and cold. This cover is made of the usual mortar, but on this occasion with no small stones in it. The Bee applies it pellet by pellet, trowelful by trowelful, to the depth of about a third of an inch over the cluster of cells, which disappear entirely under the clay covering. When this is done, the nest has the shape of a rough dome, equal in size to half an orange. One would take it for a round lump of mud which had been thrown and half crushed against a stone and had then dried where it was. This outer covering dries as quickly as the cement we use in our houses; and the nest is soon almost as hard as a stone.
Instead of building a brand-new nest on a hitherto unoccupied bowlder, the Mason-bee of the Walls is always glad to make use of old nests built the year before. These need only a little repair to put them in good condition. The Bee who has chosen one of these nests looks about to see what parts need repairing, tears off the strips of cocoon hanging from the walls, removes the fragments of clay that fell from the ceiling when the young Bee of the preceding year bored her way through it, gives a coat of mortar to parts that need it, mends the opening a little, and that is all. She then goes about storing honey and laying her egg, as she would in a new cell. When all the cells, one after the other, are thus furnished, the Bee puts a few touches on the outer dome of cement, if it needs them; and she is through.
From one and the same nest there come out several inhabitants, brothers and sisters, the males with a bright brick-red fleece, and the female of a splendid velvety black, with dark-violet wings. They are all the children of the Bee who built or repaired and furnished the cells. The male Bees lead a careless existence, never work, and do not return to the clay houses except for a brief moment to woo the ladies; they have nothing to do with the housekeeping or the new nests. What they want is the nectar in the flower-cups, not mortar to build with. There are left the sisters, who will be the mothers of the next family. As sisters, they all have equal rights to the nest. They do not go by this rule, however. The nest belongs to the one who first takes possession of it. If any of the others or any neighbors dispute her ownership, she fights them until they have the worst of it and fly away, leaving her in peace.
AN ENEMY OF THE MASON-BEE
All is not smooth sailing after the Mason-bee has finished building her dome of cells. It is then that a certain Stelis-wasp, much smaller than the Mason-bee, appears, looks carefully at the outside of the Mason-bee’s home, and makes up her mind, weak and small as she is, to introduce her eggs into this cement fortress. Everything is most carefully closed: a layer of rough plaster, at least two fifths of an inch thick, entirely covers the cells, which are each of them sealed with a thick mortar plug. The plaster is almost as hard as a rock. Never mind! The little insect is going to reach the honey in those cells.
She pluckily sets to. Atom by atom, she drives a hole in the plaster and scoops out a shaft just large enough to let her through; she reaches the lid of the cell and gnaws it till she catches sight of the honey. It is a slow and painful process, in which the feeble Wasp wears herself out. I find it hard to break the plaster with the point of my knife. How much harder, then, for the insect, with her tiny pincers!
When she reaches the honey, the Stelis-wasp slips through and, on the surface of the provisions, side by side with the Mason-bee’s, she lays a number of her own eggs. The honey-food will be the common property of all the new arrivals, the Stelis-wasp’s grubs as well as the Mason-bee’s.
The next thing for the parasite Wasp to do is to wall up the opening she has made, so that other robbers cannot get in. At the foot of the nest, the Wasp collects a little red earth; she makes it into mortar by wetting it with saliva; and with the pellets thus prepared she fills up the entrance shaft as neatly as if she were a master-mason. The mortar, being red, shows up against the Bee’s house, which is white; so when we see the red speck on the pale background of the Bee’s nest we know a Stelis-wasp has been that way.
As a result of the Stelis’ action, the poor Bee-baby will starve to death. The Wasp’s grubs mature first and eat up all the food.