ART. 2 REVISION OF TRIRHABDA NORTH OF MEXICO BLAKE 31 



Remm-ks. — The pale forms of geminata are sometimes difficult to 

 distinguish from this species. In general, nigrohunieralis is smaller, 

 and the punctation of the pronotum is not so coarse and dense. The 

 aedeagus is quite unlike that of geminata^ being small, tapering, and 

 rounded at the tip. 



21. TRIRHABDA CADUCA Horn 



Plate 2, Figure 21 



Trirhahda caduca Horn, Trans. Amer. Ent. Soc. vol. 20, p. 69. 1893. 



Description. — Oblong, coarsely punctate and moderately shining, 

 yelloAv with broad black plaga across base of head, three pronotal 

 spots, and narrow reddish-brown sutural and lateral vittae, the 

 latter evanescent in part. Head rather coarsely punctate; a broad 

 black band extending nearly across base of head and down vertex. 

 Antennae with third joint a little shorter than fifth. Prothorax 

 twice as wide as long with arcuate sides; surface shining, sparsely 

 and coarsely punctate, with the usual three spots. Scutellum either 

 entirely piceous or bordered with j^ellow, not pubescent. Elytra 

 oblong, coarsely but only moderately densely punctate, shining, very 

 indistinctly pubescent; sutural edges darkened, lateral vittae very 

 narrow and often evanescent and interrupted. Body beneath 

 entirely pale. Length, 5.5 mm. to 6.5 mm. 



Type locality. — Owens Valley, Calif. 



Distnhution. — Owens Valley, Calif. 



Remarks. — This species is one of the rarest in collections, and I 

 have seen only the original specimens of Horn. It is a very distinct 

 species and unusual in its nearly glabrous, coarsely punctate elHra 

 and short, oblong shape. It differs from eriodictyonis in its wider 

 head markings and sparser, coarser punctation, as well as in its lack 

 of pubescence and in the character of the elytral vittae. The lateral 

 vittae appear farther from the margin than those of eriodictyonis 

 and are plainly visible when viewed from above. It differs from 

 geminata and nigrohumeralis also in its lack of pubescence, coarser 

 punctation, and shining surface and in the nature of the vittate 

 markings. 



22. TRIRHABDA GEMINATA Horn 



Plate 2, Figure 22 



Trirhabda geminata. Horn, Trans. Amer. Ent. Soc., vol. 20, p. 68, 1893. 



Description. — Medium sized, rather coarsely punctate, sometimes 

 pale brown with only faint traces of reddish-brown vittae, sometimes 

 with distinctly marked lateral, sutural, and median vittae, these 

 vittae occasionally coalescing to produce nearly piceous elytra. 

 Head alutaceous with coarse obsolete punctation, moderately pubes- 



