HENRY J. FRANKLIN. 179 



read nearly every reference included in these bibliographies, 

 and the few which he has been unable to see are marked with 

 asterisks. References which have been seen and are placed 

 with doubt are marked with an interrogation point. 



A large amount of information has been collected which it 

 is impossible to include in this paper because the pressure 

 of other work does not, at present, allow time to put it into 

 shape for publication. The writer intends, however, to later 

 prepare and publish another paper on the New World Bom- 

 bidse which may be looked upon as a supplement to the 

 present work. That paper will probably deal principally 

 with methods of collecting nests, with the life histories, 

 habits and natural enemies of the two genera and with the 

 phylogeny of the family and of its groups and species as 

 shown by palaeontology, by comparative morphology and by 

 distribution. 



It is hoped that future workers on this family will go slow 

 in describing new North American species for, if such spe- 

 cies exist, they are certainly very few. It should be borne 

 in mind that the bumble-bees are conspicuous insects, and 

 that the North American species have received much atten- 

 tion from entomologists. In this connection, the fact should 

 be noticed that most of the recently described species of this 

 continent are not, in the writer's opinion, valid. To specify, 

 none af Ashmead's species and only one of Cockerell's and 

 one of Morrill's are so considered in this monograph, and 

 moreover, out of about eleven species captured north of the 

 northern boundary of Mexico and described as new, either 

 heretofore or in this work by the writer himself, only three 

 can be considered as being valid and distinct beyond ques- 

 tion. South and Central America should, however, be more 

 productive of new forms and, in both continents, there is 

 need of much investigation concerning the distribution and 

 nesting habits of the various speceies, and it is hoped that 

 this paper will give an impetus to such studies. 



The writer has experienced much difficulty in describing 

 the colors exhibited by the pile of the various species, and 

 future workers on the group, when using this paper, must 

 make allowance for this. 



TRANS. AM. ENT. SCO., XXXVIII. 



