BEES, WASPS, ANTS, ETC. 



539 



essay on the diversity of instinct, I would without hesitation point out the genus 

 Osmia." Certain species excavate the pith of brambles, alternately widening and 

 contracting the burrow to correspond with the proposed cells and the intervals 

 between them. Others bore into hard wood. Others use the hollows of reeds and 

 straws. Others again plastei- their cells thickly over the under side of some fiat stone 

 which is slightly raised from the ground. Two European species utilize the empty 

 shells of several species of Helix, compactly filling each shell with their cells, which are 

 placed in different relative positions according to the exigencies of the case, and care- 

 fully closing the entrance with pellets of claj', sticks, and pebbles. Osinia simillima 

 arranges its cells in the interior of the large, deserted gall of Diplolepis confluentus. 

 The cells of Osmia leucomelana are found in comparatively unprotected situations at 

 the roots of grass. These bees are of comparatively small size, and are usually of 



Fig. 604. — Jlci/iukile ccntuncidari-i, leaf-cutter bee ; a, male; h, female ; c, leaf-cutter at "work ; d, cell ; 



e, parts of lining of cell. 



metallic coiors. The egg is white, oblong, and about the shape and size of a caraway 

 seed. It hatches in about eight days, and the development of the larva is rapid. On 

 reaching full growth it sj)ins a delicate cocoon and winters as a pupa. Smith gives a 

 remarkable case of retarded develojiment with Osmia parieMna. From a quantity of 

 cells collected in Scotland in 1849, about one third only had given forth the adult bees. 

 Some of the remainder issued the following year, while about thirty-five remained in 

 the larva state until May, 1850, when they transformed and issued a month later. 

 The genus Megachile comprises the so-called "leaf-cutter" or "upholsterer bees." 

 It is the most universally distributed genus of bees, and is found in all parts of the 

 world. The female makes her cells of regular bits of leaf, which she cuts from a rose- 

 bush or some similar plant. The pieces of leaf are either oblong or circular, the 

 former being used for the sides, and the latter to cover the end of the cell. The bur- 

 rows in which these cells are stored vary greatly in situation. Some species burrow 

 into the ground, others into wood, while others make use of chance apertures. 



