U.S. NATIONAL MUSEUM BULLETIN 279 



Table 2. — Morphological differences between Trox and Omorgus 

 {characters pertain to larvae unless otherwise noted) . 



Trox 



1. Spiracles biforous. 



2. Maxillae with curved, diffuse 



double row or curved patch 

 of stridulatory teeth. 



3. Chromosomes metacentric.^ 



4. Antenna with prominent sensory 



cone on distal end of segment 2. 



5. Frontocylpeal suture indistinct. 



6. Extruded rectal membrane with 



elongate, continuous sclerotized 

 areas. 



7. Left mandible with two teeth (S3 



and S4) on median border 

 proximad of scissorial notch. 



8. Each anterior angle of frons with 



one seta. 



9. Tibiotarsus with two whorls of 



six setae each. 



10. 



11, 



12. 

 13. 



14. 



15. 



Prothorax with two small lateral 



lobes. 

 Prothorax without setae on dorsal, 



nonsclerotized area between 



shields. 

 DL2 of meso thorax without setae. 

 Haptolachus without sclerotized 



sense cone. 

 Glossa with four or five setae on 



dorsal aspect. 

 Rows of phobae on proximal area 



of hypopharynx curving medi- 

 ally to join at base. 



16. Pupa with two terminal claws on 



prothoracic legs. 



1 7. Adult female reproductive system 



with sbi short ovarioles on each 

 side. 



Omorgus 



1 . Spiracles cribriform. 



2. Maxillae with single, straight row 



of stridulatory teeth. 



3. Chromosomes acrocentric. 



4. Antenna without sensory cone; 



with slighdy concave sensory 

 area. 



5. Frontocylpeal suture distinct. 



6. Extruded rectal membrane with 



oval, isolated sclerotized areas. 



7. Left mandible with three teeth 



(S3, S4, and S5) on median 

 border proximad of scissorial 

 notch. 



8. Each anterior angle of frons with 



three or more setae. 

 Tibiotarsus with terminal whorl of 



six setae plus about 8 to 22 



scattered setae proximad of 



whorl. 

 Prothorax with single large lateral 



lobe. 

 1 1 . Prothorax with setae on dorsal, 



nonsclerotized area between 



shields. 

 DL2 of mesothorax with setae. 

 Haptolachus with sclerotized 



sense cone. 

 Glossa with eight or more setae on 



dorsal aspect. 

 Rows of phobae on proximal area 



of hypopharynx not curving 



medially to join at base, widely 



separated at base. 

 Pupa without terminal claws on 



prothoracic legs. 

 Adult female reproductive system 



with three long ovarioles on 



each side. 



9. 



10 



17 



» Testes from males of known ages were used by Dr. N. Virkki, University of 

 Puerto Rico, Agricultural Experimental Station, for the studies of the chromosomes. 



