The group Scopulipedes includes such long-tongued, solitary bees as are not parasitic, and do not belong to the Dasygastres. It is not, however, a natural group, for the carpenter-bees (Xylocopa) are very different from Anthophora. It has recently been merged by Friese with Andrenides into a single group called Podilegidae. Four British genera, Ceratina, Anthophora, Eucera and Saropoda (including, however, only seven species), are referred to the Scopulipedes; in some forms a considerable resemblance to the Bombi is exhibited, indeed the female of one of our species of Anthophora is so very like the worker of Bombus hortorum var. harrisellus, that it would puzzle any one to distinguish them by a superficial inspection, the colour of the hair on the hind legs being the only obvious difference. Anthophora is one of the most extensive and widely distributed of the genera of bees. Some of the species make burrows in cliffs and form large colonies which are continued for many years in the same locality. Friese has published many details of the industry and metamorphoses of some of the species of this genus; the most remarkable point he has discovered being that A. personata at Strasburg takes two years to accomplish the life-cycle of one generation. Some of the European species of the genus have been found to be very subject to the attacks of parasites. An anomalous beetle, Sitaris, has been found in the nests of A. pilipes; and this same Anthophora is also parasitised by another beetle, Meloe, as well as by a bee of the genus Melecta.
The genus Xylocopa[[27]] contains many of the largest and most powerful of the bees, and is very widely distributed over the earth. In Europe only four or five species have been found, and none of them extend far northwards, X. violacea being the only one that comes so far as Paris. They are usually black or blue-black in colour, of broad, robust build, with shining integuments more or less covered with hair. X. violacea is known as the carpenter-bee from its habit of working in dry wood; it does not touch living timber, but will form its nest in all sorts of dried wood. It makes a cylindrical hole, and this gives access to three or four parallel galleries in which the broad cells are placed; the cells are always isolated by a partition; the bee forms this by cementing together with the products of its salivary glands the fragments of wood it cuts out. Its habits have been described at length by Réaumur, who alludes to it under the name of "abeille perce-bois." This bee hibernates in the imago condition, both sexes reappearing in the spring. Possibly there is more than one generation in the year, as Réaumur states that specimens that were tiny larvae on the 12th of June had by the 2nd of July consumed all their stock of provisions; they then fasted for a few days, and on the 7th or 8th of July became pupae, and in the first days of August were ready to emerge as perfect Insects. Thus the whole cycle of metamorphoses is passed through in about eight weeks. This species, though very clever in drilling holes, does not hesitate to appropriate old burrows should they be at hand. Fabre observed that it was also quite willing to save itself labour by forming its cells in hollow reeds of sufficient calibre. We have figured the larva and pupa of this species in the previous volume (p. 170).
Fig. 17.—Xylocopa (Koptorthosoma), sp. near flavonigrescens, ♂. Sarawak.
Xylocopa chloroptera in E. India selects a hollow bamboo for its nidus; it cements together the pieces obtained in clearing out the bamboo, and uses them as horizontal partitions to separate the tube into cells. The species is much infested with a small Chalcid of the genus Encyrtus: 300 specimens of the parasite have been reared from a single larva of the bee; two-thirds of the larvae of this bee that Horne endeavoured to rear were destroyed by the little Chalcid.
The most beautiful and remarkable of all the bees are the species of Euglossa. This genus is peculiar to Tropical America, and derives its name from the great length of the proboscis, which in some species surpasses that of the body. The colours in Euglossa proper are violet, purple, golden, and metallic green, and two of these are frequently combined in the most harmonious manner; the hind tibia is greatly developed and forms a plate, the outer surface of which is highly polished, while the margins are furnished with rigid hairs. Very little is known as to the habits of these bees; they were formerly supposed to be social; but this is doubtful, Bates having recorded that E. surinamensis forms a "solitary nest." Lucas concluded that E. cordata is social, on the authority of a nest containing "a dozen individuals." No workers are known. The species of Eulema have a shorter tongue than Euglossa, and in form and colour a good deal resemble our species of Bombus and Apathus.
The group Dasygastres includes seven European genera, four being British (Chelostoma being included in Heriades). The ventral surface of the hind body is densely set in the females with regularly arranged hairs, by means of which the pollen is carried. In many of the Dasygastres (Megachile, e.g.) the labrum is very large, and in repose is inflected on to the lower side of the head, and closely applied to the doubled-in tongue, which it serves to protect; the mandibles then lock together outside the labrum, which is thus completely concealed. This group includes some of the most interesting of the solitary bees.
Fig. 18.—Euglossa cordata, ♂. Amazons. A, The Insect with extended proboscis; B, outer face of hind tibia and tarsus.
The genus Chalicodoma is not found in our own country, but in the South of France there exist three or four species. Their habits have given rise to much discussion, having been described by various naturalists, among whom are included Réaumur and Fabre. These Insects are called mason-bees, and construct nests of very solid masonry. C. muraria is in appearance somewhat intermediate between a honey-bee and a Bombus; it is densely hairy, and the sexes are very different in colour. It is solitary in its habits, and usually chooses a large stone as a solid basis for its habitation. On this a cell is formed, the material used being a kind of cement made by the Insect from the mixture of a suitable sort of earth with the material secreted by its own salivary glands; the amount of cement used is reduced by the artifice of building small stones into the walls of the cell; the stones are selected with great care. When a cell about an inch in depth has been formed in this manner, the bee commences to fill it with food, consisting of honey and pollen; a little honey is brought and is discharged into the cell, then some pollen is added. This bee, like other Dasygastres, carries the pollen by means of hairs on the under surface of the body; to place this pollen in the cell the Insect therefore enters backwards, and then with the pair of hind legs brushes and scrapes the under surface of the body so as to make the pollen fall off into the cell; it then starts for a fresh cargo; after a few loads have been placed in the receptacle, the Insect mixes the honey and pollen into a paste with the mandibles, and again continues its foraging until it has about half filled the cell; then an egg is laid, and the apartment is at once closed with cement. This work is all accomplished, if the weather be favourable, in about two days, after which the Insect commences the formation of a second cell, joined to the first, and so on till eight or nine of these receptacles have been constructed; then comes the final operation of adding an additional protection in the shape of a thick layer of mortar placed over the whole; the construction, when thus completed, forms a sort of dome of cement about the size of half an orange. In this receptacle the larvae pass many months, exposed to the extreme heat of summer as well as to the cold of winter. The larvae, however, are exposed to numerous other perils; and we have already related (vol. v. p. 540) how Leucospis gigas succeeds in perforating the masonry and depositing therein an egg, so that a Leucospis is reared in the cell instead of a Chalicodoma.