LEAF-CUTTER BEE.
Few hymenoptera of the family of bees are so little known as the Megachilidæ, or Leaf-cutters. They are stout, thick-bodied insects, with large, square heads, and armed with sharp, scissors-like jaws, which admirably fit them for the work they have to do in preparing materials for the building of their homes.
Our commonest species, Megachile centuncularis, is about the size of the hive-bee. In gardens and nurseries where shrubbery abounds, it is very prevalent, especially the female, which is readily distinguished by a thick mass of stout, dense hair on the under side of the tail, which serves as a carrier of pollen. The honey- and bumble-bees differ materially from them, for they have the hind tibiæ and basal joints of the tarsi very much broadened for that purpose.
Megachile is by no means a remarkable-looking insect. Judging from its very humble exterior, one can hardly believe it possessed of the wonderful intelligence, as shown in its wise provisions for its young, which it is found to display.
Ordinarily the female, who is entrusted with the discharge of this very essential business, places her nest in the solid earth underneath some species of shrub. A vertical hole, three inches in depth, is dug, and this is enlarged into a horizontal gallery, some five or six inches in length.
You should see the little creature in her never-tiring work of preparing material for her nest. In and out among the roses she goes, examining each leaf with the most critical care, and only desisting from her labor when a suitable one has been chosen. She scans it over and over, and at last from a position on its upper or nether surface proceeds to cut a piece just fitted for her work, which, heavy as it seems, is seized between the legs and jaws and carried on swiftly-agitated wings to her burrow.
LEAF-CUTTER BEE AT WORK.
Two Tunnels Being Filled With Leaf-Cells.
Ten pieces or more, each differing in shape, are cut and borne away, which the ingenious insect tailor twists and folds, the one within the other, until is formed a funnel-like cone, whose end is narrower than its mouth. So perfectly joined are the parts, that even when dry they have been found to retain their form and integrity. A cake of honey and pollen, for the use of some yet unborn Leaf-cutter, is deposited within, and on this, in due time, is laid a single small egg. Nought now remains but to wall up the cell. A circle of leaf, of the size of the opening, is cut, and this is closely adjusted within the wall of rolled-up leaves. Sometimes as many as four pieces are thus utilized. A second cell, similarly built, is fitted to the first, and this is succeeded by eight or ten others. When all is completed, the eggs being laid and the cells all victualled, the hole of the shaft is closed with the earth that was thrown out, and so carefully, too, that not a trace of her doings remains to tell us the story.
Like other insects, Megachile is occasionally prone to change. Some laborers while digging, one early spring-day, some thirteen years ago, about a cluster of plants of Spiræa corymbosa, a species allied to the roses and cinquefoils, came unexpectedly upon a dozen or more cells of this insect, arranged horizontally in layers, some three or four inches below the ground’s surface. These cells were three-fourths of an inch in length, one-fourth in width, and formed of the leaves of Spiræa. Six circles, of three pieces each, constituted the cell, and these were so arranged that each succeeding circle was made to project but slightly beyond its predecessor. Six circular pieces, larger than seemed needful, closed up the opening of each cell. That there was a purpose here manifested was very apparent. This purpose, as it appeared to the writer, was the better accommodation by the hollow surface of the cell that was to follow, and the giving of greater firmness and security to the entire structure.
More curious, however, were some cells that were found the ensuing year, which, in looks, resembled very closely those of Pelopæus, a species of wasp, familiarly designated the Mud-dauber. These cells, in numbers of three, were adherent to the rafters of a hardly-used garret. In form, and in the peculiar combination of their pellets of clay, they were the exact counterpart of the Mud-dauber’s. But the curious funnel-like arrangement of leaves on the inside, so strikingly characteristic of the Megachilidæ, was evidence of the most positive kind that Pelopæus had nothing whatever to do with their putting together. It bespoke a piece of work that was entirely beyond the highest capability of her being to execute.
Each of the included leafy cells was one and one-eighth inches in length, and just barely exceeding one-fourth in width. Elliptical pieces of Spiræa, less in size than those previously described, but arranged in a similar manner, composed the several structures. Within each, a dead but perfectly-formed Megachile, encased in a cylindrical bag of silk, was found, so that there could be no possible doubt of the builder. That this inner fabric was the labor of some mother Megachile admits not of a scruple, for no other bee is known to construct a nest of like character. But what of the outer enveloping fabric of mud? It was clearly impossible for the skill of a Megachile, who, while certainly fitted for tunnelling the ground and for snipping circular and elliptical pieces of suited dimensions from leaves with all a tailor’s precision, would find herself wofully unadapted for the making of mortar and the building of nests, in imitations of tunnels, out of pellets of mud that had to be moulded into consistency and shape by the jaws of the builder. Pelopæus alone, of all hymenopters, possesses the ability and means of making such structures. Megachile, who is known to occasionally build under the boards of the roof of a piazza, might sometimes in her quest of a place appropriate the discarded cells of some pre-existent Pelopæus for nesting purposes, but she runs a very great risk in so doing, for the Mud-dauber does not always build a fresh home for her treasures, save when there is a lack of the last year’s structures. Old nests, when found, are put in speedy repair and made to do as invaluable a service.