LARVAL TAXONOMY OF THE TROGINAE IN NORTH AMERICA 17 



The larvae of Trox and Omorgus have a large, strongly pigmented 

 cranium which varies in color from orange, red, or brown to dark red 

 brown or black. The cranium is slightly reticulate posteriorly and 

 slightly rugose anteriorly and bears a small number of setae in a well- 

 defined pattern. The cranium also is strongly pitted in some species. 

 The sclerotized shield of the prothorax is usually of a color similar to 

 that of the cranium. 



The larvae bear two specialized structures which are probably egg 

 bursters on DLl of the mesothorax and metathorax. The bursters are 

 thorn-like sclerotized projections bearing a short seta on the posterior 

 side near the base (fig. 15). They are located on each side of the dorsal 

 median line slightly anterior to the transverse row of setae. The bursters 

 are larger on the metathorax and they are generally larger on larvae 

 of Trox than on larvae of Omorgus. The egg bursters are present in 

 second and third stage larvae in a much reduced condition. 



The pupae are of the exarate type (figs. 32 and 34) and are sexually 

 dimorphic. The ventral aspect of abdominal segment eight in the 

 females has two lobes flanking a slightly depressed median area (fig. 13). 

 The ventral aspect of abdominal segment eight of the males has two 

 lateral lobes flanking a median lobe (fig. 14), The setal pattern anterior 

 to the lobes is also slightly difl'erent for the males and females (figs. 1 3 

 and 14). Pupae of the two genera are separable in that the more slender 

 prothoracic legs of Trox bear a pair of terminal claws which are lacking 

 on the stouter prothoracic legs of Omorgus (figs. 30 and 31). 



Life History 



The following life history was worked out for Trox scaber (L.) in the 

 laboratory, at room tempeature. The female from which all the larvae 

 were reared was collected on April 26, 1965, at black light about 10 

 miles north of Corvallis, Oreg., by the writer. 



This female was placed in a pint jar two-thirds filled with screened 

 sand which was overlaid with about one-half inch of hair and feathers. 

 The female deposited a total of 11 eggs during the first 7 days of 

 captivity. These were deposited in groups of three and four at 2- to 3- 

 day intervals. Egg production then decreased to an average of three to 

 four eggs about every 5 days during the next 16 days. It then decreased 

 again in July and ceased altogether about July 15, 1965. A total of 

 58 eggs and larvae was retrieved from the container. 



The female oviposited at a depth of about 1 to 3 mm. beneath the 

 food source. The larvae hatched about 8 to 9 days after oviposition. 

 First stage larvae burrowed to the surface, where they fed in a well- 



