188 BEES OF GREAT BRITAIN. 



joint elavate-truncate, attached to its side near the apex. The 

 maxillary palpi three-jointed. The anterior wings have one 

 marginal and two submarginal cells ; the second submarginal 

 receiving the two recurrent nervures. Abdomen sublinear, 

 slightly narrowed towards the base ; furnished in the female with 

 a dense scopa of pubescence. In the male, the abdomen is 

 incurved and dentate at the apex. 



This genus is very closely related to Heriades, and on a care- 

 ful examination of the parts of the mouth it will be found 

 that the A. campanularum belongs to the genus Chelostoma - 9 

 the maxillary palpi are three-jointed in both genera ; but the 

 labial palpi are differently formed, although consisting of the 

 same number of joints, as will be seen on a reference to the 

 figures ; the wings are the same in both genera. 



The species of the genus Chelostoma form their burrows in 

 decaying posts, rails, &c. ; but when they chance to meet with 

 ready-formed tubes, like other bees, as we have shown, they 

 have the sagacity to avail themselves of such conveniences. 

 Some years ago I found a colony of these bees in the straw 

 tubes of a thatched barn ; and similar examples are to be seen 

 amongst the collection of nests of hymenopterous insects in the 

 British Museum. In the observations on the genus Osmia is 

 given an account of the operations of these bees, and it is 

 only necessary to add some notice of the parasites and enemies 

 by which their broods are attacked. Mr. Marsham* gives an 

 account of the proceedings of Pimpla manifestator introducing 

 its eggs into the nests of these bees, but it is scarcely proved that 

 the larva of Chelostoma was the object of attack : when we take 

 into consideration the size of the parasitic larva and that of the 

 bee, we are inclined to suspect that the Pimpla' 's attack was upon 

 some other insect. Where colonies of this bee are met with in 

 posts and rails, there are usually also two Coleopterous insects, 

 Melandrya caraboides and Clytus arietis, depositing their eggs ; 

 they may be frequently observed thrusting their ovipositors, or 

 elongated apical segment of the abdomen, into the burrows of 

 the bees ; this is probably merely for the purpose of introducing 

 them into the wood in a suitable situation, the larva of both 

 beetles feeding on the wood : it is possible that Pimpla attacks 

 the larva of one of these insects, and not that of Chelostoma. 

 The only Ichneumon which I know from observation to be a 

 parasite on Chelostoma is Fcenus assectator : this insect has more 



* Trans. Linn. Soc. iii. 26, 



