NORTH AMERICAN COLEOPTERA. 201 



In the males the hist ventral segment is truncate, the pygidium 

 vertical and convex ; in the female the last ventral is oval and the 

 pygidium horizontal. 



As represented in our fauna, Disonycha is far more homogeneous 

 than Qi]dionychis, the species not exhibiting any marked structural 

 differences among themselves, consequently any attempt at tabula- 

 tion is more or less based on coloration, which seems to be quite con- 

 stant as to type, but variable in degree. 



The genera with which Disonycha is associated are extremely 

 difficult to separate by sharply drawn characters. The species of 

 Haltica have the tibise longitudinally sulcate, but in a less marked 

 degree The base of the thorax, although generally regularly arcu- 

 ate, is in some species quite oblique each side as in Disonycha. 

 Phrynocepha is especially indistinct, the more so when we consider 

 the species at present referred to it. 



The species at j)resent known to me may be separated by the fol- 

 lowing table, the arrangement in a sequence by facies is shown by 

 the numbers : 



Form elongate, parallel, elytra subsulcate ; thorax rather irregularly convex ; 



elytra yellow, with black vittje 1. peniisylvanica. 



Form more or less oval, elytra even ; thorax regularly convex 2. 



2. — Elytra vittate 3. 



Elytra with large discal spot black 10. discoidea. 



Entire body above black, subopaque 11. f'liiierea. 



Elytra dark violet, blue or green g. 



3. — Elytra with a submarginal vitta 4 



Elytra without submarginal vitta 7. 



4.— Abdomen densely punctured, subopaque, the pubescence conspicuous 5. 



Abdomen very sparsely punctured and shining, pubescence scarcely visible..6. 

 5. — Head coarsely punctured from side to side, occiput piceous or brown. 



2. quinquevittata. 



Head smooth at middle. 



Elytral vittse rather broad, head and metasternum more or less fuscous or 



piceous, labrum piceous 3. creiiieollis. 



Elytral vittfe narrow, head and body beneath always pale yellow ; labrum 



pale 4. caroliniaua. 



6. — Thorax distinctly punctured. 



Head smooth at middle ; epipleurie pale 5. arizonte. 



Head with coarse, deep punctures; epipleuraj black 6. iliarJtima. 



Thorax smooth ; head rough; epipleurse black 7. glabrafa. 



7. — Median elytral vitta broad ; antennje normal ; thorax not spotted. 



8. abbreviata. 



Median vitta extremely narrow; antennse slender, three-fourths the length 



of body; thorax with two spots 9. teniiicoriiis. 



TRANS. AM. ENT. SOC. XVI. (26) .JUNE, 1889. 



