4 PROCEEDINGS OF THE NATIONAL MUSEUM vol. hj 



Methods 



In the course of this study most of the larger collections of North 

 American Onthophagus were examined by one or both of the authors. 

 Almost all the distribution data contained in this paper were taken 

 from specim.ens personally examined; most place names were taken 

 from pin labels and obvious misspellings have been corrected by the 

 authors. Complete data are given only when less than 20 specimens 

 of a species are known or when all are from one or two localities. In 

 addition to borrowed material, all the type material available in the 

 eastern United States and Canada was studied. Type specimens 

 were borrowed from museums in London, Berlin, and Munich, and 

 specimens were compared with types in Paris, as stated in acknowl- 

 edgments. 



Descriptions of adults are based entirely on external characters. 

 Male genitalia were found useful in some species, but proved more 

 difficult to use than the external characteristics. Separation of 

 closely related forms by characters of the genitalia appeared impos- 

 sible, and for that reason descriptions of genitalic features have 

 been omitted. 



Additional adult material and much of the biological information 

 was procured personally during extensive trips (see Acknowledgments, 

 p. 1). 



Adult specimens were collected at dung, carrion, or fungi, and by 

 trapping. Traps were made of tin cans, the 16 to 32-ounce sizes, with 

 the tops cut out, sunk level with the ground surface and partly filled 

 with dung, fungi, or a fermenting bait. One of the more successful 

 baits was a mixture of one pint of malt extract to one gallon of water 

 with a pinch of di'ied yeast added. An inch of the fermenting mixture 

 was poured in the sunken can and usually 2 to 3 cc. of propionic acid 

 was added to the can. The malt by itself attracted mainly the fungus 

 feeders; the acid was attractive to the dung feeders. The mixture 

 attracted both of these groups in numbers. 



Many of the rarer species were found in animal nests or burrows and 

 were seldom, if ever, taken outside of their particular niche. Occa- 

 sional specimens were taken at light. Some of the more unusual 

 habitat niches in which Onthophagus have been found are wood rat 

 nests, gopher tortoise burrows, prairie dog burrows, woodchuck 

 biu-rows, and caves containing bat dung. Other types of mammal 

 and bird nests were also investigated, but generally proved unpro- 

 ductive. 



Larvae of a number of the species were obtained by simply placmg 

 adults in 12-inch soil-filled flower pots covered with a piece of glass. 

 Fresh dung was placed on top of the soil in the pot and the beetles left 

 undisturbed for several weeks. In nearly all cases where a number 



