Revision of the FOSSORIAL HYMENOPTERA of North America. 

 I. Crabronid.e and Nyssonidje. 



BY A. S. PACKARD, Jr., M. D. 

 [Bead November IZth, 1865.] 

 When two years since, with scanty material consisting of the more 

 common forms, we began to study this most interesting group of Hy- 

 menoptera, it seemed a comparatively easy matter to decide upon what 

 seemed truly generic and specific forms. Characters which we must 

 now consider of scarcely subgeneric value, were unhesitatingly pro- 

 nounced to be of full generic importance, and in some cases simple 

 varieties were thought to be good species. The large sub-divisions of 

 Crabro, of which C. singular is, 0. arcuatus, and C. inferruptus are 

 types, were considered of generic value, and some of St. Fargeau's 

 genera, which we now reject, were adopted. But the great influx of 

 species made known to us by the writiugs of Mr. Frederick Smith of 

 the British Museum, published in the Catalogue of Hymenoptera, and 

 the more recent articles of Mr. E. T. Cresson in the Proceedings of this 

 Society on the hymenoptera of Colorado Territory, collected by Mr. 

 Biding^, and of Cuba, which formed the collection of Prof. F. Poey, 

 together with much new material most liberally loaned me by Mr. Ed- 

 ward Norton, E. T. Cresson and the Boston Society of Natural History, 

 which last is especially valuable as giving us several of Say's and Dr. 

 Harris' types;* has materially changed our views on the classification of 

 the group. Thus our notions as to the value of different natural groups 

 daily fluctuate with each new influx of species, so that it seems as if the 

 natural system which every student strives after, were at the mercy of the 

 opinion of each inquirer, changing and differing from other systems 

 according to the stand point from which he regards nature. Our own 

 impression received from the study of so difficult a group as the one 

 under present consideration, is that our arbitrary and stiff systems can 

 never express in words or in diagrams the unceasing variation and 

 change of characters, now constant, and now slight and shifting, which 

 take place in natural groups. Our notions of genera and species are 

 in a great measure ideal and typical rather than real and fixed. Our 

 descriptions, when good and reliable, are not descriptions of a single 



More special acknowledgment of aid in preparing this paper, will be made 

 in ike descriptions below. 



