LARVAL TAXONOMY OF THE TROGINAE IN NORTH AMERICA 9 



terrestris group is distinguished by having six sensory pegs on the distal 

 portion of the terminal segment of the antenna (figs. 44 and 47). The 

 other three groups have five sensory pegs and one long sensory seta 

 (figs. 45 and 46). 



It appears that Vaurie's tuberculatus and unistriatus groups are closely 

 allied on the basis of larval characteristics. The larvae of these groups 

 could not be separated one from the other, and several larvae of the 

 tuberculatus group are so similar that they have been brought out to- 

 gether in the same key couplet. 



The larvae of the genus Omorgus are generally much larger than those 

 of TVo.v, and with a few exceptions are much more setiferous. Certain 

 of the species are quite distinct and easily recognized. Others, however, 

 are so similar that the writer cannot separate them by reliable key 

 characters. 



Species groups within the genus Omorgus are evident on the basis of 

 larval characters. 0. monachus and 0. fuliginosus are the only species to 

 possess spinules but no setae on DL 1 of the first four abdominal segments. 

 All other species possess both. 0. rubricans and 0. texanus are distin- 

 guished from the other species by the large concavity mediad of the eye- 

 spot and by the transverse row of caudally directed phobae at the base 

 of the smaller distal portion of the hypopharynx. The larvae of the 

 other six species of Omorgus are apparently much more homogeneous. 



Methods and Materials 



Collection of Specimens 



The four species of Trox and Omorgus which are known to occur in 

 Oregon were collected at black light and a method for rearing the 

 larvae was worked out during the summer of 1963. The majority of 

 the remaining species ( 1 5) were collected at black light or at carcasses 

 on an extended trip through Arizona, New Mexico, and Texas during 

 June and July of 1964. Other species were collected by interested 

 workers and airmailed to Corvallis, Oreg., for rearing. Two shipments 

 of specimens were received from South America, but all specimens 

 died en route.* Additional preserved larvae were obtained from the 

 United States National Museum and Dr. P. O. Ritcher. 



The black light setup consisted of one 15-watt General Electric 

 F15T8-BL tube placed on each side of a cloth sheet which was sus- 



* Transportation or shipment of living specimens was done with State and Federal 

 permission. 



