110 . GEORGE H. HORN, M. D. 



Description of tlie species of APHODIUS and DIALYTES of the United 



States. 



BY GEO. H. HORN, M. D. 



The fullowiug essay presents to the student a list of all the species 

 of Aphodius known from North America, north of Mexico, and con- 

 tains the results of many years careful collection of specimens from 

 every region of our country by personal labor or through the kindness 

 of many correspondents who have all promptly responded to the re- 

 quest for the loan and gift of specimens. The basis of the work was 

 found in the admirable collection of Dr. Leconte, and around this all 

 new species have been arranged. Several types of Alaskan species 

 have been of much value in determining their correct positions as well 

 as those of allied forms unknown to us in nature. 



The species have been arranged in groups for the most part equiva- 

 lent to those of Erichson (Insecten Deutschlands) while several new 

 ones have been indicated for our West Coast species. 



The genus Dialtjtes Harold, (Coleopterologische, Hefte V, 1869, p. 

 101) differs from Aphodius in the structure of the anterior tibise on 

 which the 'two upper teeth are obsolete, the third at the angle and 

 acute, while the fourth is anterior and projects forward over the in- 

 sertion of the tarsus. The head is strongly deflexed, the front not 

 carinate nor tuberculate. Eyes partially hidden. 



A fuller comparison of the genera will be made when sufficient 

 time shall have elapsed for the completion of the remaining species 

 and genera of the tribe. 



APHODIUS, II] ig. 

 Our species of Aphodius have become quite numerous in collections 

 but present various characters by Avhich they may be divided into 

 groups, each containing but small series of species, and the study is 

 therefore rendered comparatively easy. We may divide the genus pri- 

 marily into two sections; 



Scutellura elongate, equaling i or one-fifth the length of Ihe elyir a,... Section I. 

 Scutellum short, as broad or broader than long, never ex- 

 ceeding in length i or one-tenth the length of the elytra Section II. 



Section I is composed entirely of large species, in our fauna, al- 

 though not containing all our large speics. It may be again sub-divi- 

 ed as follows. 



c^' 



