AKT. 17. LARVAE OF HOLARCTIC TIGER-BEETLES HAMILTON. 65 



tance between ocelli, 1 and 2, 0.17 mm.; length of fronto-clypeo- 

 labral area, 1.6 mm., width, 1.4 mm.; length of pronotum, 1.7 mm., 

 width, 3 mm. 



This larva was collected March, 1911, by Dr. E. A. Schwarz at Porto 

 Bello, Panama, in a dead branch of a tree among a colony of ants. 

 Its structure indicates that it belongs to the arboreal group. Because 

 of its importance morphologically it has been included and placed 

 tentatively in the genus Gtenostoma Klug. 



5. Genus OMUS Eschscholtz. 



Head with the ridge on the caudal part of frons transverse and 

 continuous with the ridge on the caudal part of vertex; latero- 

 clypeus distinct, crescent-shaped; anterior margin of the labrum 

 crenulate; ocellus 2 about one-half the size of ocellus 1, ocelli 3 and 4 

 distinct, subequal in size, ocellus 5 small, conical, and distinct, ocellus 

 6 about one-half the size of ocellus 5, small and indistinct; antenna 

 not separated from the mandible by a transverse, chitinized bar, the 

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

 segment about one-half the length of the second; maxilla with the 

 ventral sclerite of the cardo triangular and bearing two setae; a 

 small spine, possibly a rudimentary lacinia, present on the inner and 

 distal margin of the stipes, maxillary palpus three-segmented, the 

 segments increasing slightly in length from the proximal to the dis- 

 tal, the proximal segment without a spine on the latero-distal mar- 

 gin; labio-stipites not depressed on the middle and without a carina 

 on the lateral and caudal margins; ligula not chitinized on the ven- 

 tral aspect ; palpiger area with two chitinized sclerites separated by 

 a flexible suture; labial palpus with the proximal segment longer 

 than the distal segment and with a single spinelike projection on its 

 ventro-distal margin, the proximal segment with two setae and the 

 distal segment with one; fifth abdominal segment with the inner, 

 median, and lateral hooks present, the lateral hooks short and bear- 

 ing from six to eight setae, the median hooks long, the proximal half 

 cylindrical and the distal half thornlike, slightly curved ventrad, 

 and with two setae at about the middle, inner hooks about one-half 

 the length of the median hooks, the proximal two-thirds cone- 

 shaped and with two setae at its distal part, the distal one-third 

 thornshaped and projecting cephalad. 



This genus occurs only on the Pacific coast from British Columbia 

 to the southern part of California. There are a number of species 

 and sub-species, the adults of which are difficult to separate. The 

 larvae are also very difficult to separate, and a study of a large series 

 would probably aid in the nomenclature of the adults. 

 45554— 2&—Proc.N.M.vol.65 3G 



