32 HYMENOPTERA CHAP. 



with ; it is the interest of the parasite to avoid annoyance and to 

 be well-mannered in its approaches. Shuckard, however, says that 

 battles ensue between the parasite Melecta and its host Anthopliora, 

 when the two bees meet in the burrows of the Anthophora. 1 



We shall have occasion to remark on some of the habits of 

 Dioxys cincta when considering the history of the mason -bee 

 (Chalicodoma), but one very curious point in its economy must 

 here be noticed. The Dioxys, which is a much smaller bee than 

 the Chalicodoma, lays an egg in a cell of the latter, and the 

 resulting larva frequently has more food in the cell than it can 

 consume ; there is, however, another bee, Osmia cyanoxantlia, that 

 frequently takes advantage of an unoccupied cell in the nest 

 of the Chalicodoma, and establishes its own offspring therein. 

 The Dioxys, it seems, cannot, or at any rate does not, distinguish 

 whether a cell is occupied by Chalicodoma or by Osmia, and some- 

 times lays its egg in the nest of the Osmia, though this bee is 

 small, and therefore provides very little food for its young. It 

 might be supposed that under these conditions the Dioxys larva 

 would be starved to death ; but this is not so ; it has the power 

 of accommodating its appetite, or its capacity for metamorphosis, 

 to the quantity of food it finds at its disposal, and the egg laid in 

 the Osmia cell actually produces a tiny specimen of Dioxys, only 

 about half the natural size. Both sexes of these dwarf Dioxys are 

 produced, offering another example of the fact that the quantity 

 of food ingested during the lifetime of the larva does not influ- 

 ence the sex of the resulting imago. 



The highly endowed bees that remain to be considered are 

 by some writers united in a group called Apidae, in distinction 

 from Andrenidae. For the purposes of this work we shall adopt 

 three divisions, Scopulipedes, Dasygastres, Sociales. 



The group SCOPULIPEDES includes such long-tongued, solitary 

 bees as are not parasitic, and do not belong to the Dasygastres. 

 It is not, however, a natural group, for the carpenter-bees 

 (Xylocopa) are very different from Anthopliora. It has 

 recently been merged by Friese with Andrenides into a single 

 group called Podilegidae. Four British genera, Ceratina, AnfJio- 

 pliora, Eucera and Saropoda (including, however, only seven 



1 It is impossible for us here to deal with the question of the origin of tin- para- 

 sitic habit in bees. The reader wishing for information as to this may refer to 

 Prof. Perez's paper, Act. Sue. Bordeaux, xlvii. 1895. p. 300. 



