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True Bees — Part 3

After the tunnels are prepared the cells are made and supplied with pollen. With the species under consideration the cells are about seven-tenths of an inch long, and are separated from each other by partitions which are made up of a single flattened band of sawdust and fine chips glued together and rolled up into a flat partition about four layers deep. The side forming the bottom of the cell is concave and smooth, while the other side is flat and rough.

Even about the common carpenter bee there is much yet to be learned, and a careful series of studies carried through an entire season cannot fail to show novel facts.

The mason bees of the family Megachilidae (sub-family Osmiinae) derive their name from the manner in which they construct small earthen cells under stones, in the burrows of other bees, in decaying wood, in deserted snail shells, in old galls, and elsewhere. These bees show a great diversity of habit. Their cells are constructed of sand, earth or clay mixed with pebbles and wood scrapings, but glued together so firmly that they are smooth inside. Ten to twenty of them are usually found together, and each one contains a store of honey and pollen, for the larvae, of which only one is found in each cell.

One of these bees (Ceratosmia (Osmia) lignivora Packard) has been shown by Dr. Packard to be a true wood-borer. He saw it make a tunnel three inches long in maple wood, the tunnel containing five cells and the partitions being made of wood chippings.

The leaf-cutting bees of the same family are common creatures whose habits are extremely interesting. They derive their name from the fact that they cut pieces out of the tender leaves of various trees with which to form their cells. The leaf-cutters are found in all parts of the world and look much like bumble-bees. The pieces of leaf which they cut out very neatly are either oblong or circular, the former being used for the sides and the latter to cover the end of the cell. The burrows which they use vary greatly in situation. Some burrow into the ground, others into soft wood, while others make use of chance tunnels. I have seen them in accidental auger holes, and in lead pipe, and once knew the nozzle of an old pump to be packed full of cells. According to Professor Putnam, a single female observed by him took twenty days to complete and provision a series of cells under a board. He found there were thirty cells in nine rows of varying numbers. An estimate of the number of bits of leaf used in the construction of these thirty cells amounted to more than a thousand.

The potter bees of this same family construct small globular cells of earth and attach them to the stem of a plant.

The parasitic bees of the family Stelidae live, like the Nomadidae, in the nests of other bees, choosing indifferently the cell of almost any kind of bee, no matter what its situation. No observations on any of the American species have been recorded, and here is an interesting field of study.

The habits of the European species Stelis minuta have been observed with some care. It was found to be parasitic in the nest of one of the mason bees, a female having laid her egg in the cell after it was partly filled by the mason bee. Unaware of the presence of the parasitic egg, the mason bee continued her work, and after nearly filling the cell deposited her own egg on the top of the food mass, closing the cell with a partition, and beginning another one above. The Stelis larva hatched a little earlier than that of the mason bee, and both began to feed, the parasite larva from below and the mason bee larva from above. Unfortunately for those who are interested in the triumph of right and justice, the latter grows very slowly while the parasite larva grows more rapidly, and gradually worked its way upward through the food mass, thus approaching the mason bee larva. In the words of Riley's summary of this tragic performance "the crisis finally comes--the Stelis larva encounters the Osmia larva; a short but deadly combat ensues; the Osmia larva is easily overpowered and killed by the much larger and stronger parasite, and its body is devoured by the latter within one or two days."

The sharp-tongued burrowing bees form a very large group, with many common species which fly actively through the summer. The cells as a rule are made in burrows or tunnels in the ground or in hard clay banks. Andrena vicina, according to Emerton, digs a straight tunnel into the ground for a depth of several inches or more with short oblique galleries branching off from it. The earthen cells lined with mucus are filled with pollen and honey. This is all done in the latter part of April and early in May. The larvae are full grown in less than five weeks, and the adult bees issue all through July and August. To this group belong the beautiful little bees of the genus Halictus, which are often metallic in color. They dig branched tunnels to a depth of from six to ten inches and are semi-gregarious in habit, a great many of the burrows often being found close together. Emerton has studied the habits of H. parallelus, and states that this bee has two generations each year.