2 U.S. NATIONAL MUSEUM BULLETIN 2 79 



forms which are washed ashore. The larvae of several species have 

 been reported feeding on the eggs of the migratory locusts in Asia, 

 Africa, and South America (Denier, 1936; Hayward, 1936; Gardner, 

 1946; RofTey, 1958). The two genera have a nearly worldwide distri- 

 bution, being more common in desert and semidesert regions. Forty- 

 two species of Trox and Omorgus are known at present in North America 

 (Vaurie, 1955, and Howden and Vaurie, 1957). In this report the 

 larvae of 24 species are described, 18 for the first time, and the pertinent 

 morphological structures are illustrated. 



At the commencement of this study the larvae of most of the major 

 groups within the Scarabaeoidea were fairly well known. The more 

 comprehensive works include the following : Aphodiinae Qerath, 1 960) ; 

 Coprinae (Ritcher, 1 945c) ; Gcotrupinae (Ritcher, 1 947, and Howden, 

 1955); Melolonthinae (Ritcher, 1949, and Boving on Phyllophaga only, 

 1942); RuteUnae (Ritcher, 1945a); Dynastinae (Ritcher, 1944); 

 Cetoniinae (Ritcher, 1945b); and Hayes (1929) and Boving and 

 Craighead (1931), who were concerned primarily with the taxa above 

 the species level. 



Each of the above subfamilies has also been treated by Ritcher (1966) 

 in his comprehensive work on the scarabaeoid larvae of North America, 

 along with additional sections on the Glaphyrinae, Hybosorinae, 

 Pleocominae, Acanthocerinae, and Troginae and the families Luca- 

 nidae and Passalidae. Ritcher's treatment of the Troginae is the most 

 extensive to date for North America, and includes figures for the 

 larvae of four species of Trox. 



This study of the immature stages was undertaken to help clarify 

 the taxonomic status of the Troginae. The placement of the Troginae 

 within the Scarabaeidae has varied with different workers. Certain 

 workers, among them Edwards (1949) and Crowson (1955), have 

 given the group family status. This writer is in agreement with those, 

 among them Arnett (1960), Vaurie (1962), and Ritcher (1966), who 

 would retain the group as a subfamily within the Scarabaeidae. Com- 

 parative studies on the larval musculature and larval nervous system 

 are currently in progress and should aid in the systematic placement of 

 the various subfamilies.^ The high degree of syminetry in the structures 

 of the epipharynx and hypopharynx of Trox and Omorgus are indicative 

 of the generalized condition. This is in agreement with the findings 

 of Sharp and Muir (1912), who would derive the male aedeagus of all 

 the scarabaeid subfamilies from that of the Troginae. 



Prior to this study the larvae of six species of Trox and Omorgus were 

 known from North America. Four of these six species ha\'e been reared 



' Personal communication with Dr. F. H. Butt, Route 1 , Box 47C, Friday Harbor, 

 Wash. 



