HABITS OP XYLOCOPA. 167 



pTetty little Ceratina may be inserted contiguous to the 

 continental and exotic Xylocopa. The latter constitute 

 a very numerous genus, for we are acquainted with more 

 than a hundred species, and they are the largest and most 

 bulky of all known bees ; the female of the oriental X. 

 latipes being more than an inch in length, and two inches 

 in expansion. These are most truly carpenter bees ; and 

 as they occur numerously in countries fertile in timber, 

 and of an exuberant vegetation, one purpose of their 

 economy may be to hasten its decomposition when dead, 

 by exposing it to the internal access of wet and fungi, 

 by the large lengthy longitudinal perforations they make 

 to deposit their young in security. They are subjected 

 in the West Indies to the parasitical attacks of the cole- 

 opterous genus Horia ; and probably, in other countries, 

 other parasites prey on them. This genus presents some 

 difficulties in its study, arising from the uniform in- 

 tensely black colour of the greatest number of the species : 

 their wings, which are of a brilliantly metallic steely 

 blue or coppery colour, have been referred to as affording 

 safe specific diagnostics ; but we think incorrectly, for 

 they are liable to all the contingencies of age and use : 

 the sculpture of the clypeus we consider presents a 

 safer clue. In the great majority of this genus, nothing 

 but direct observation can bring together the genuine 

 partners of the same species, as in very many instances 

 the males are yellow or fulvous, and the females black 

 or metallic. Here, as in Nomia and Halictus, we ob- 

 serve the species diverging in structure from the type. 

 In some males we detect a dilatation of the anterior 

 tarsi, as in Megachile; but these appear linked to the 

 more normal form by means of the fulvous species, which 

 have the anterior tarsi densely ciliated. Another diver- 

 gent form from Western Africa, which has the inter- 

 mediate legs very long and spined, and with curled locks 

 of hair, has been raised, unduly we think, to the rank of 

 a genus, by the name of Mesotrichia, and has been con- 

 sidered as linking Xylocopa to Anthophora, by means of 

 those species of the latter which also have males with 

 M 4 



