BRITISH HYMENOPTERA. 211 



Family I. — Andrenidje. 

 Genus Colletes. 



The economy of the insects which compose the present genus has been fre- 

 quently quoted from the interesting history given by Reaumur, who found 

 them constructing their burrows in the interstices of stone walls — the spaces 

 between the stones no doubt being filled with earth or some soft kind of 

 mortar; they are found burrowing in light sand-banks. One species, C. Da- 

 viesana of Kirby's MSS., is extremely abundant in many sandy districts, par- 

 ticularly in the county of Kent; where, as I learnt on having an opportunity 

 of examining Mr. Kirby's own interleaved copy of "The Monographia," he 

 himself had observed it, near Maidstone. The burrows of these insects are 

 from eight to ten inches in length; they are lined at the further end with a 

 very thin transparent membranaceous coating, resembling gold-beater's skin: 

 the insect having stored up a sufficient supply of pollen and honey in a semi- 

 fluid state, closes up the cell with a cap of the same substance as the lining 

 of the tube; this cap is stretched flat across, like the parchment on a drum- 

 head; a little within she next constructs a concave cap, serving as the end of 

 the . cell ; her former labour is then repeated until she has furnished six or 

 eight cells, when the whole is completed. There is little doubt that the same 

 bee constructs more than one of these tubes, as there never appears any trace 

 of a second tunnel running into the first, as may be observed in many other 

 species of solitary bees, particularly Halicti, Andrenidce, and Anthophoridce. 

 These bees are subject to the attacks of two parasites, one feeding upon the 

 larva?, the other upon the pollen; the first is a Dipterous insect, Miltogramrna 

 punctata; these flies are very frequently to be seen entering the burrows of 

 the bees, and have been often bred from the cocoons of Colletes; the second 

 parasite is the beautiful little bee, Epeolus variegatus, which has been very 

 frequently reared from the cells of Colletes. 



These bees are gregarious, forming large colonies, particularly the C. Davie- 

 sana; and although their numbers are to some extent reduced by the parasites 

 named, still . their destruction by these means sinks into insignificance when 

 compared to the wholesale slaughter committed upon them by Forficula; these 

 omnivorous enemies devour indiscriminately pupae, larvae, or pollen; and in 

 some situations they abound to such an extent, that not less than three-fourths 

 of the bees perish through the attacks of these destructive insects. 



There are four known British species of this genus, the type being the Apis 

 succincta of Linnaeus: the authentic specimen is preserved in the cabinet at 

 the Linnsean Society's Museum. 



Genus Peosopis. 



The bees of which the present genus is composed, being destitute of the 

 usual apparatus for collecting pollen, were long regarded as belonging to the 

 family of parasites. Some years ago two of the species were bred from bramble 

 sticks, the larvae having been exposed and found to be arranged in the same 

 regular order as in the acknowledged industrious, or working species: this 

 observation was made by Mr. Thwaites in 1841. Since that time I have re- 



