158 BEES OF GREAT BRITAIN. 



joint minute. The superior wings with one marginal and two 

 submarginal cells, the second submarginal cell receiving the two 

 recurrent nervures. 



In the female the head is usually very large, subquadrate, the 

 ocelli placed forward on the vertex in a slight curve ; the abdo- 

 men furnished with a dense pollen-brush beneath. 



Males usually resembling the females, but more slender, having 

 the antennae longer, and the apex of their abdomen generally 

 armed with spines or teeth. 



If I were asked which genus of bees would afford the most 

 abundant materials for an essay on the diversity of instinct, I 

 should without hesitation point out the genus Osmia. I propose 

 to notice in this place all that has occurred to me during an 

 attentive observation of their economy for the last twenty years. 

 Mr. Kirby in the ' Monographia Apurn Angliae,' has quoted the 

 history of Reaumur's Mason-bee, which although not included 

 in the present genus, is still so nearly allied, that its history 

 might be taken as a parallel to that of Osmia ; but as it is not 

 a British species, I merely allude to it, to call attention to the 

 highly interesting history given by Reaumur of its economy. 

 The most abundant species is Osmia bicornis ; its economy is 

 varied by circumstances; in Killy country, or at the sea-side, it 

 chooses the sunny side of cliffs or sandy banks, in which to 

 form its burrows ; but in cultivated districts, particularly if the 

 soil be clayey, it selects a decaying tree, preferring the stump of 

 an old willow ; it lays up a store of pollen and honey for the 

 larvae, which when full-grown spin a tough dark brown cocoon, 

 in which they remain in the larva state until the autumn, when 

 the majority change to pupae, and soon arrive at their perfect 

 condition ; many however pass the winter in the larva state. In 

 attempting to account for so remarkable a circumstance, all must 

 be conjecture, but it is not of unfrequent occurrence; this 

 species also frequently makes its burrows in the mortar of old 

 walls. Osmia leucomelana may be observed availing itself of a 

 most admirable, and almost ready, adaptation for a burrow ; it 

 selects the dead branches of the common bramble ; with little 

 labour the parent bee removes the pith, usually to the length of 

 from five to six inches ; at the end she deposits the requisite 

 quantity of food, which she closes in with a substance resembling 

 masticated leaves, evidently vegetable matter; she usually forms 

 five or six cells in one bramble-stick. The bee does not extract 

 the whole of the pith, but alternately widens and contracts the 

 diameter of the tube, each contraction marking the end of a cell ; 



