CLASSIFICATION OF THE BEES. 65 



and have undoubtedly originated from other bees, through different 

 lines of descent. It is evident, however, that most of them are de- 

 scendents from various Anthophorid bees, since they agree more 

 nearly with these bees in venation and the characters of the mouth 

 parts than with any of the others. 



They are easily distinguished from the Anthophoridse, however. 

 by color, by the 9 having no polleniferous scopa, or at most with 

 only a very short, sparse pubescence, and by their bodies being most 

 frequently bare or nearly, the pubescence, if any, being short ami 

 sparse. Very rarely are they densely pubescent on the head and 

 thorax, as in the Anthophoridse. The species are metallic, or rufous 

 and black, or rufous and yellow, the abdomen being most frequently 

 ornate with yellow or white maculse or bands. 



Some of them also resemble quite closely some of the Stelididse, 

 another family of parasitic bees; but the latter have only two sub- 

 marginal or cubital cells in the front wings, while the labrum is, as 

 a rule, not so well developed nor so prominent and always strongly 

 inflexed. I believe also that the Stelididse had quite a different line 

 of descent, or from the Megachilidse, their characters agreeing more 

 nearly with this family than with any other. 



The numerous genera, now placed in the Nomadidse, may be dis- 

 tinguished by the use of the following table : 



Table of Genera. 



Marginal cell at apex not separated from the costa 17. 



Marginal cell at apex rounded, always separated from the costa or trioleate. 



Cubital cells, along the cubitus, nearly of an equal length, the first as a rule 



somewhat the longest cell 11 



Cubital cells, along the cubitus, of an unequal length, one or another most fre- 

 quently longer or much smaller, the first usually much the longest, or 

 at least somewhat the longest (very rarely with the third the longest 

 Third cubital cell, along the cubitus, longer than either the first in- 

 second 13. 



Third cubital cell, along the cubitus, equal to the first or distinctly 



shorter 2. 



2. First cubital cell, along the cubitus, much longer than the third, sometimes as 



long as the second and third united :;. 



First cubital cell, along the cubitus, equal or nearly equal to the third, never 

 very much longer. 

 Second cubital cell either petiolate or very much narrowed above: marginal 

 cell elliptical, not or only a little longer than the first cubital cell, or 

 less than half the length of the first discoidal cell ; SCUtellum sub- 

 bilobed ; axilhe rounded behind ; abdomen short, subglobose as viewed 

 from above: labial palpi 3-jointed, the first joint stoat, longer than 2 3 

 united ; claws with a tooth or cleft /aro^mia Aslim. 



TKANS. AM. KNT. SOC. XXVI. (9) JUNE. 1899. 



