ART, 17. LARVAE OF HOLAKCTIC TIGER-BEETLES HAMILTON. 67 



the caudal margin bearing two groups of four setae each ; inner hooks 

 five-eighths the length of the median hooks and with two setae; 

 median hooks with two setae ; lateral hooks with five to seven setae. 



Measurements. — Length of larvae, 26 to 28 mm., width at the 

 third abdominal segment, 3.2 to 3.4 mm.; diameter of ocellus 1, 

 0.51 to 0.54 mm., of ocellus 2, 0.36 to 0.38 mm.; distance between 

 ocelli 1 and 2, 0.29 to 0.31 mm. ; length of f ronto-clypeo-labral area, 

 2.4 to 2.6 mm., width 2.7 to 2.8 mm. ; length of pronotum, 2.9 to 3.2 

 mm., width 5 to 5.2 mm. 



The larvae were collected at Alhambra Valley, Contra Costa 

 County, California, December 29, 1905, by Dr. F. E. Blaisdell, sr. 



OMUS AMBIGUUS Schaupp. 

 Figs. 47, 86, and 121. 



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

 University of Illinois. 



Color. — Head dark brown or bronze, the cephalic portion between 

 the mandibles lighter; pronotum dark chestnut brown, slightly 

 lighter than the caudal part of the head; setae on dorsal aspect of 

 head and pronotum dark brown, the other setae light brown. 



Head. — Setae on dorsal aspect long, stout, and prominent; diame- 

 ter of ocellus 2 equal to the distance between ocelli 1 and 2 ; f ronto- 

 clypeo-labral area wider than long; transverse ridge on the caudal 

 part of frons bearing five setae, the middle seta much larger than 

 those on each side; cephalic margin of the labrum with the crenu- 

 late emarginations shallow, the median lobe distinctly wider than 

 those on each side (fig. 47) ; antenna with the proximal segment 

 slightly longer than the second, the third as long as the second, and 

 the fourth slightly more than 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, the proximal segment of the 

 labial palpus with a single spinelike projection on the ventro-distal 

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

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



Thorax. — Pronotum with the cephalo-lateral angles extending 

 slightly cephalad of the mesal portion, lateral margins slightly 

 carinate, setae more than 60 in number (fig. 86). 



Abdomen. — Chitinized areas distinct; secondary setae numerous 

 and prominent, lateral margins of tergal sclerites usually bearing 

 three large, adjacent setae (fig. 121) ; ninth abdominal sternum with 

 the caudal margin bearing two groups of four setae each ; inner hooks 



