AMERICAN COLEOPTERA. 291 



three grooves (rnhrolineatd), often one only as in vlttata^ or with a con- 

 futed punctuation (some specimens of Xereuc). In his essay on the 

 Chrysomelidae (Proc. Acad. 1873, p. 82) Crotch included Octotoma in 

 Microrhopala. The genus seems sufficiently marked to retain as dis- 

 tinct. Our species, although not numerous, are not easily separable in 

 tabular form. The following table will assist in their recognition : 



Terminal joint of tarsi very little or not longer than the lobes of the third ; an- 



tennal club elongate 2. 



Terminal joint of tarsi nearly twice as long as the lobes of the third; antennal 



club rather short 10. 



2. — Elytra with eis;ht series of punctures only •">. 



Elytra with more than eight series 9. 



3. — Joints 2-6 of antennae nearly smooth and glabrous \ it lata. 



Joints 2-6 roughly sculptured and somewhat hairy 4. 



4. — Body above bicolored, thorax generally with lateral red stripe, elytra visually 



vittate 5. 



Body above entirely blue or slightly greenish 6. 



Body above bicolored, elytra yellow, apical half and suture black, 



dimidiata. 

 5. — Surface above and beneath black, rarely feebly bronzed Xerene. 



Surface above and beneath bright blue. 



Thorax with lateral red vitta, elytral vitta narrow rubroliiieata. 



Thorax without vitta, elytral vitta broad \ uliicrata. 



6. — Thorax not or very little wider at base than apex floridana. 



Thorax gradually wider from apex to base 7. 



7. — The rows of punctures regular and distinct 8. 



Rows of punctures very irregular, the punctures large and confluent, 



Erebus. 

 8. — Punctures of the outer rows much larger and of more irregular size than the 



inner cxcavata. 



Punctures of all the rows equal and distinct cyauea. 



9. — The interval between the third and fourth costae with four series of punctures 



near the apex; form slender, parallel porcata. 



10. — Above and beneath black molilalia. 



Above reddish yellow, elytra maculate with black, thorax on each side with 

 a distinct basal impression jflelsheimeri. 



As the species are for the most part common and well-known, detailed 

 descriptions seem unnecessary, and only the more important characters 

 and variations will be mentioned. 



]>I. \ ittata Fab. — Oblong ovate, bluish black, head, thorax, base of femora, 

 elytral vitta and narrower side margin red. Antennae nearly smooth to the sixth 

 joint. Front unisulcate. Elytra with eight series of punctures arranged in pairs, 

 the alternate intervals broader and slightly more convex. Length .20-. 26 inch: 

 y-6.5 millim. 



Var. laetula Lee, has the head and thorax more clearly red than in 

 the Eastern forms. Kansas to Oregon. 



