CHARLES W. HOOKER. 25 



larly broken and appendiculate, but a good series of O. bifo- 

 veolatus, chilensis and a few others shows at once that in 

 these species it is sometimes only angularly bent or almost 

 arcuate and the appendix rudimentary or entirely wanting. 

 The character of the surface of the metathorax also varies 

 markedly, as in bilineatus, where it varies from smooth or 

 slightly reticulate to distinctly reticulate. The ocelli are nor- 

 mally medium sized, but in O. costale they are as small as 

 in Thyreodon. 



Table of Species. 



1. Wings subfuliginous or fuliginous 2. 



Wings hyaline, only slightly fuscous or fulvous 6. 



2. Discocubital vein arcuate, nervellus broken at or above the middle..3. 

 Discocubital vein angularly broken or appendiculate, nervellus 



broken at or below the middle 5. 



3. Posterior ocelli connected with the tops of the eyes by a deep black 



furrow costale Cress. 



Posterior ocelli not connected with the tops of the eyes by a deep 

 black furrow 4 . 



4. Eyes small, thoracic sutures, pleurae, pectus and mesothorax partly 



black bifoveolatus nigrovarius Prov. 



Eyes not small, thoracic sutures not marked with black. 



5. Abdomen long and slender, antennae shorter than the body. 



bilineatus elongatiis n. subsp. 

 Abdomen not long and slender, antennae longer than the body. 



slossonse Davis. 



6. Abdomen stout, not strongly compressed ; eyes small, distant from 



the base of the mandibles bifoveolatus Br. 



Abdomen usually strongly compressed 7. 



7. Eyes small, distant from base of mandibles 8. 



Eyes not small, not distant from base of mandibles 12. 



8. Base of discocubital vein twice angularly broken, appendix directed 



downward abuoriuis niagiuiceps n. subsp. 



Base of discocubital vein not twice angularly broken, appendix 

 not directed downward 9. 



9. Antennae black melaiiostig-nia Cam. 



Antennae not black 10. 



10. Ocelli small, the posterior connected with the tops of the eyes by a 



deep black furrow bilineatus nigrovarius Br. 



Ocelli not small, not connected with tops of eyes by a deep black 

 furrow 11. 



11. Wings hyaline (or slightly fuscous) 16. 



Wings with distinct fulvous tinge coloradensis Felt. 



TRANS. AM. BNT. SOC. , XXXVIII. (4) 



