146 JOURNAL OF ENTOMOLOGY AND ZOOLOGY 



head. In most species tliere are sixteen ocelli present. The 

 postantennal ori>an is nsnally present and is of importance in 

 species determination. The claws are two and often bear teeth 

 on inner and outer margins. The furcnla may be poorly 

 develo])ed or well develoi)ed and the mncrones are more highly 

 developed in this genns than in any of the others. 



Key to the Genus Isotoma 



A. Fnrcnla short, not reaching ventral tnbe. 

 B. Mncrones bidenticnlate. 



0. C^laws unarmed; manubrium longer than dentes ; 

 antennae little longer than the head; gray-bine 

 or brown. bidenticula 



CC. Snperior claw armed; dentes twice the length 

 of the mannbrinm; antennji^ same length as 

 head; light green in color. (ujiice n. sp. 



BB. Mncrones tridenticulate. 



C Mncrones with second and third teeth opposite. 

 D. Claws unarmed. hesselsii 



J)T). Claws armed; superior, two teeth on 

 inner margin, two on outer; inferior, one 

 tooth on inner margin. aspera n. sp. 



CC. Mncrones with second and third tooth not oppo- 

 site, third tooth smaller ; claws unarmed. 



mini))! a 

 A A. Furcnla reaching nearly or quite to the ventral tube. 



B. Mncrones, tridenticulate ; no regular markings ; inner 

 margin of superior claw bidentate; postantennal 

 organ ovate to oval. viridis 



BB. Mncrones quadridenticulate. 



C. Long pre-apical tooth, minute apical tooth ; 

 claws armed ; length 3 mm. catena 



.CC A])ical tooth of mncrones projecting as far as 

 pre-apical. Dorsal median dark stripe. 



palustris 



