PKEFACE. 



The work that has served as a basis for this volume has ex- 

 tended over several years, and has been done in Wisconsin, at 

 the residence of Dr. Charles A. Leuthstrom, to whose forbear- 

 ance in allowing us to use his gardens as a hunting-ground, we 

 are greatly indebted. The field is a most favorable one since 

 an island in the lake close by, acres of woodland all about, and 

 a farm with two vegetable gardens, one on the top of a hill and 

 one on lower ground, offer a rich variety of nesting places. It 

 is in the lower garden, which is bounded by woods, that the 

 wasps are found in greatest abundance. 



The study of the solitary wasps was suggested to us by those 

 most interesting and delightful of all entomological papers, 

 the "Souvenirs Entomologiques" of J. H. Fabre, and however 

 widely our conclusions may differ, we have for M. Fabre and 

 for his work, the deepest respect and admiration. 



We wish to express our indebtedness to Mr. W. H. Ashmead 

 of Washington, for his cordial interest in the work and for his 

 kindness in identifying for us the various species. 



Milwaukee, October 30, 1897. 



