THE LIFE AND HABITS OF THE SOLITARY BEE MEGACHILE by
T H I S bee has by its habits acquired for itself various English craftsmen-like names, three of which are, the Carpenter, the Woodcarver and Leaf-cutter bee, all are befitting as will become apparent in the following account.
A solitary $ of this species began to burrow approximately one and a half inches under the extremely hard surface of the wood, working its way into and with the grain. Entry was made at the broken end of a large root of an upturned Beech tree at Fornham Park during July - August, 1953. The wood was in the process of decay and was dry and firmer than touch-wood. The bee worked rapidly, excavating its burrow by biting into the wood and dropping the sawdust-like pieces, moving them back under the abdomen with its forefeet, and as it made progress these were gradually pushed out, the whole being pushed out by the abdomen as the bee occasionally left the work for various periods. Upon reaching the required length of its burrow, it proceeded to trim it, beginning at the inner end. It moved head foremost towards the entrance moving the head in a slow side to side motion, opening and closing the mandibles, which snipped off the rough misshapen pieces, and vibrating the wings which kept in motion a current of air which blew the debris before it and out of the burrow. The vibrations caused a high pitched buzz which was audible at a distance, and sounded much like that of a fly caught in a web. This completed the excavation of its burrow. It next selected and cut pieces of various shapes from the leaves of a nearby Sycamore tree, Acer pseudoplatanus, with which it constructed the cells. These pieces were cut from the outside of the leaves and retained the toothed edges ; the first pieces cut were roundish and with some variations', measured 10 m.m. across. These were brought and placed at the end of the burrow to form the base of the first cell. The next four were of various lengths, 22 - 24 m.m. and their breadth irregulĂ¤r owing to the toothing of the leaves, at most 11 m.m. wide ; these were placed round the wall of the burrow, with the joins lapped and so placed that the cut margin was within the toothed edge and the end turned inward and over the base pieces. The cell was now capable of holding the liquid which was to be stored therein. The bee next visited the flowers of the Spear Thistle, Cirsium vulgare, and the Creeping Thistle, Cirsiutn arvense, from which it collected nectar and pollen, and made it into a mixture of honey and pollen and stored it in the cell; an egg was then probably deposited therein. And now to complete
LIFE AND HABITS OF BEE
the construction of the cell it again visited the Sycamore tree and cut from its leaves a further eight or more roundish pieces which it used to seal it. These were of the same size as those used to form the base. T h e top ends of the pieces which formed the lining were now turned inward and each seal piece was placed singly on top and each agglutinated round the edges and to the wall of the burrow with a dark green substance, the whole appearing as if pressed down and shaped, leaving a concave finish and a wonderfully constructed base for the next cell, the whole when revealed appearing like a row of miniature green cigars. When the nest was removed and opened, it was shown first that the bee after burrowing to a distance of three inches had come upon a sealed lateral burrow and cell of a species of solitary wasp Metacrabro quadricinctus ; it had then withdrawn one inch to continue its burrow away f r o m the obstruction at an angle of 72°, working a length of three quarters of an inch before it again turned into the grain of the wood and proceeded straight to complete the burrow with a length of 9 | inches and a breadth and depth with slight variations of 8 m.m. T h e nest was incomplete and contained three cells ; two were complete, the first at extreme inner end measured in length 16 m.m., the second, 19 m.m. The length of the bee measured was 15 mm. and the whole of this work had taken it approximately 10 days. DIA GRAM
NEST i• / 'f- INeues BELOW the
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DIRECTION OF CRA/N
Further. In transporting each piece of leaf, the bee held it in a semicircular position between its legs and under the abdomen, the hollow facing down and slightly to one side. U p o n alighting at the entrace it quickly disappeared carrying the leaf into the darkness of its burrow. On three separate occasions when M. ligneseca was returning to her nest, laden with a collection of mauvish white thistle pollen, she was followed by another bee of about her own size and colour,
LIFE AND HABITS OF BEE
which probably had parasitic intentions. Upon arrival it loitered swinging and circling in front of the next hole, and it was not until M. ligneseca was well within her burrow that the other bee settled near the entrance, but it was not observed to enter. DĂźring August, 1954, a nest belonging to this species was removed from this site. The bee in excavating its burrow had strictly followed the grain of the wood, and this was shown at the commencement where a steep rise and turn was encountered. T h e overall length of the burrow measured six inches, and appeared to have contained four cells, but only two complete ones and part of a third remained, the fourth had by some unknown predator been completely destroyed, only the dark green marks of the agglutinating sealing substance showed its former whereabouts. Remarks. When these nests were removed care was taken not to disturb the complete cells, and since, so long as they have remained, no bees had emerged by December, 1958. An old tattered grey-brown cell, from which no bee had emerged, was taken from a burrow at this site, and it appeared that the bee during its construction had been over-industrious in applying the seals, these were difficult to separate, but ten were counted, and to judge from their thickness probably for each of these another two could be added. S O M E HABITS OF ANOTHER SPECIES OF THIS FAMILY OF SOLITARY
BEESâ€”MEGACHILE WILLUGHBIELLA, KIBBY. A $ of this species was observed constructing her nest in a large log of willow Salix alba, L. var. coerulea (Sm.) Sm at West Stow Sewage Farm during July, 1955. The log was one of the foundation pieces to a loosely stacked pile, the wood was rotten and saturated with water, and in this and next under the thick bark, the bee had excavated its burrow, reaching to a length of five inches. T h e nest contained four complete cells and one under construction, these were constructed with pieces of leaves which it had most elegantly cut from the Silver Birch Betula verrucosa, Ehrh. In the construction of the cells the pieces were transported and placed in exactly the same way as has been described in the habits of the foregoing species Megachile ligneseca. T h e length of the pieces which lined the burrow of each cell, were of various lengths, 19 m.m. - 21 m.m., and the breadth at the narrow end, 9 m.m., and at the wide end, 12 m.m., in which the bee had incorporated in the cut a part of the natural curve of the leaf, before ascending or descending, in a line approximately 3 m.m. from the stalk, the seals were round except for 4 m.m. of leaf margin and measured 9 m.m. across. The length of a complete cell was 17 m.m. and that of the bee, 13 m.m.