NATURAL SCIENCES OF PHILADELPHIA. 141 



basal joints of flagellum long, subequal ; thorax gibbous, feebly 

 punctured, shining; seutellum flat, metathorax opaque, witli well- 

 defined elevated lines, apex truncate ; wings ample, areolet 5-an- 

 gular ; legs slender; abdomen elongate, flattened, petiolate, smooth 

 and polished. Length 3^ lines. 

 Orizaba. 



Genus MESOSTENUS, Grav. 

 Subgenus Polycyrtus, Spinola. 



This subgenus is distinguished by having a single spine or 

 tubercle on the front, behind the antenna?. The form is long and 

 very slender in all the species ; the three regions of the meso- 

 thorax prominent ; the first abdominal segment long, slender, and 

 gradually but not broadly dilated at apex ; and the areolet of an- 

 terior wing closed. 



The species may be tabulated as follows : 



Abdomen black, banded with white or yellowish : 

 Metathorax with cruciform black mark above : 



Second abdominal segment with a white sublunate mark on each side, 



and third segment with a white lateral spot 1. melanoleucus. 



Sides of second and third segments broadly margined with white. 



2. ferox. 



Metathorax with a central black stripe, often dilated medially and crossed 



by a slender line near base : 



Second abdominal segment with a subtriangular white mark on basal 



middle, and an elongate white mark on lateral margin. ... 3. major. 



Second abdominal segment with a sublunate mark on each side and 



lateral margin, white 4. acerbus. 



Second abdominal segment with a large, acute, cruciform mark on 



basal middle and a spot on lateral margin, white 5. macer. 



Second abdominal segment with an irregular, transverse, central mark 



near base 6. mancus. 



Second abdominal segment with basal half of lateral margin dilated ; 



metathorax broadly black at base 7. paululus. 



Metathorax with two black spots at base, and a central black stripe. 



8. junceus. 

 Metathorax with three black stripes, the lateral ones confluent at base, 



the central one short ; mesothorax with a central white spot. 



9. reliqiius. 

 Metathorax entirely honey -yellow, sometimes stained with fuscus ;it base 



above 10. copiosus. 



