66 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.65. 



TABLE TO THE SPECIES OF THE GENUS OMUS. 



Cephalic margin of the labrum with the crenulate emarginations deep; pro- 

 notum distinctly lighter colored than the head; tergal sclerites of the ab- 

 domen with two large, adjacent setae on the lateral margin. 



californicus, p. 66. 



Cephalic margin of the labrum with the crenulate emarginations shallow; 



pronotum but little, if any, lighter colored than the head; tergal sclerites 



of the abdomen usually with three large, adjacent setae on the lateral 



margin 1 



1. Cephalic margin of the labrum with the median crenulate lobe distinctly 

 wider than those on each side ; pronotum with more than sixty setae. 



ambiguus, p. 67. 



Cephalic margin of the labrum with the median crenulate lobe not distinctly 



wider than those on each side; pronotum never with more than fifty setae. 



sequoiarum, p. 68. 



DESCRIPTION OF SPECIES. 



OMUS CAUF0RN1CUS Eschscholtz. 



Figs. 3, 12, 13, 19, 25, 30, 35, 44, 46, 82, 83, 84, 118, and 119. 



Blaisdeli,, reared, larvae in the collection of Dr. A. D. MacGillivray. 

 University of Illinois. 



Color. — Head dark bronze or black, uniformly colored; pronotum 

 light chestnut brown; setae on dorsal aspect of head and pronotum 

 the same color as the head, the other setae light brown. 



Head. — Setae on dorsal aspect long, slender, and prominent; 

 diameter of ocellus 2 slightly greater than the distance between 

 ocelli 1 and 2; fronto-clypeo-labral area wider than long; trans- 

 verse ridge on caudal part of frons bearing five setae, the middle 

 seta much larger than those on each side; cephalic margin of the 

 labrum with the crenulate emarginations deep, the median lobe 

 not distinctly wider than those on each side (fig. 46) ; antenna 

 with the proximal, second, and third segments subequal in length, 

 the distal segment one-half the length of the second, the proximal 

 segment with four or five setae and the second with five or six; 

 maxilla with the proximal segment of the galea bearing three 

 setae on its mesal margin; ligula with four fine setae arranged 

 in a transverse row on its ventro-distal end, proximal segment of 

 labial palpus with a single spinelike projection on the ventro- 

 distal margin and with a single seta on each side of this spine, the 

 proximal segment with two setae and the distal segment with one. 



Thorax. — Pronotum with the cephalo-lateral angles extending as 

 far cephalad as the mesal portion, lateral margins slightly carinate, 

 setae not more than 40 in number (fig, 84). 



AhdoTTien. — Chitinized areas distinct; secondary setae short and 

 not numerous and with two large, adjacent setae on the lateral mar- 

 gin of the tergal sclerites (fig. 119) ; ninth abdominal sternum with 



