NORTH AMERICAN NEUKOPTKRA. 



329 



7.-Tarsi o-jointed NEUROPTERA 8. 



Tarsi 2- 3- or 4-jointed CORKODENTIA 9. 



8.— Mouth rostrated >■ MECAPTERA. 



Month not rostrated PLANIPENiNIA. 



9. — Wings with many veins, prothorax distinct. TERMITIN.A.. 



Wings with few veins, prothorax indistinct PSOt'INA. 



10.— Mouth rostrated MECAPTERA. 



Mouth not rostrated H- 



11.— Tarsi 4-jointed, prothorax distinct TERMITINA. 



Tarsi 3-jointed 12. 



12. — Prothorax inconspicuous, no caudal setaj PSOCINA. 



Prothorax distinct, two caudal setfe PLECOPTERA. 



Order PL.ATYPTERA. 



Suborder PLECOPTERA. 

 PERLID^. 



The body is long, soft and depressed ; the antennre h)ng and seta- 

 ceous. The mouth-parts are well developed. The larvte are aquatic. 

 and usually found under stones in running water. The adults are 

 called "stone-flies." 



Fig. I. — A Perlid. 

 I, costal; 2, subcostal; 3, radius; 4, cubitus : 5, postcubitus ; 6, radial sector ; P, pter- 

 ostigma; A, arculus; ai, 2, 3, apical cells. 



Key to Genera. 



1. — Wings with many transverse irregular veins I'teroiiarcys. 



Wings with few more regular transverse veins 2. 



2. — Subniarginal apical space with some transverse veins 3. 



Submarginal apical space without transverse veins 4. 



3. — Imago with external branchiie l>it'tyO|>(('r,>'x. 



Imago without external branch iaj Acroiieiii'ia. 



4.— Caudal setie present ~y. 



Caudal setas absent 10. 



5. — All palpal joints equally thick I'apiiia. 



Last palpal joint thinner, filiform (j. 



6. — Hind wings broader than fore wings, anal space present 7. 



Hind wings not broader than fore wings, anal space absent. ..IsO|»tory.\. 

 7. — Between costaand radius, bej'ond end of subcosta, at least three cross- veins.. 8. 



Between costa and radius beyond end of subcosta, but one cro.ss-vein. 



C'liloroperla. 



TRANS. AM. ENT. SOC. XIX. (42) DECEMBEK, l^ilj. 



