CHARLES W. HOOKER. 107 



Ocelli small, separated from the tops of the eyes bj' about twice their 

 diameter; wings without stigma; discocubital vein arcuate, not appen- 

 diculate ; nervellus usually broken well above the middle ; nervulus 

 usually postf ureal to interstitial; claws pectinate; abdomen com- 

 pressed. 



Generic type. — T. cyaneus Br. 



The species of this genus are large, often bright colored 

 insects, usually more or less extensively marked with black 

 on both body and wings- They are closely related to mem- 

 bers of the Genus Athyreodon, but may be recognized by their 

 small ocelli. The Ophions may be readily distinguished by 

 the presence of a stigma, discocubital vein usually angularly 

 broken and appendiculate, nervellus usually broken below 

 the middle and the wings usually hyaline, while the ocelli 

 are usually larger. A few species, however — O. costale, bifo- 

 veolatus, etc. — sometimes at least, have these characters as 

 in Thyreodon except for the presence of a distinct stigma. 

 These specimens are always smaller than the Thyreodons, 

 and the wings are not distinctly marked with black. 



The Genus Thyreodon was proposed by Brulle in 1846 for 

 three strictls'^ American species — T. cyaneus, morio and mar- 

 ginipe7inis. The generic type was not designated and, so far 

 as I can learn, has not yet been. I therefore designate T. 

 cyaneus Br. as the generic type, in accordance with the In- 

 ternational Code of Nomenclature, Recommendations, Art. 

 30, Sect. N, as revised by the Seventh Congress ; by which 

 preference is given to the best described, best known, etc. 

 T. cyaneus was the first described — by Brulle, was well known 

 at the time and a good colored plate was given. Taschen- 

 berg mentions the Genus Thyreodon in 1876, but considers it 

 synonymous with the Genus Ophion. All later writers have, 

 however, considered it valid. 



Distribution. — This genus includes about twenty species 

 and subspecies of which all but two, one from Japan and one 

 from Borneo, are American. The American species are with 

 a few exceptions tropical, but T. morio ranges as far north 

 as Quebec and Stonewall, Canada, and T. marginipennis 

 comes from Uruguay and Argentina. T. morio and taticinctus 



TRANS. AM. ENT. SOC. , XXXVIII. 



