244 TERTIARY INSECTS OF NORTH AMERICA. 



teristics the American plant lice appear as a rule to differ from forms so far 

 described from the European Tertiaries. The single winged species figured 

 \)y Berendt from amber, however, shows precisely this character as far as 

 the length of the stigmatic cell is concerned, which is about two-fifths the 

 length of the wing. These figures are incorrectly copied by Buckton, with 

 the remark that the neuration is abnormal, which it certainly is in his figure. 

 It will be interesting to know whether the other species of the Baltic amber 

 will .show a similar departure from the condition of the stigmatic cell in 

 modern types. Not a single one of the Florissant forms can be referred to 

 an existing genus. 



Table of the genera of Aphides. 

 Cubital vein twice forked Apllidiiiie. 



Cubital veiu arising at less than half the distance from the first oblique to the stigmatic vein. 



Stigmatic vein arising midway between the first and second forks of the cubital vein or dis- 

 tinctly nearer the second fork. 

 Origin of the stigmatic vein midway between the first and second forks of the cubital vein. 



Apex of cell about three times as broad as its base 1. Cataneura. 



Apex of cell about ,si\ times as broad as its base '2. ArchilacJinim. 



Origin of the stigniatie vein scarcely or not before that of the second fork of the cubital 



vein. 

 Base of second oblique vein several times nearer the first oblique than the cnliilal 



vein 3. Geranchitm. 



Base of the second oblique vein midway between the first oblique and the cubital 



vein 4. Sbenaphis. 



The stigmatic veiu arising opposite the first fork of the cubital vein or distinctly nearer it 



than the second. 

 First cubital branch nearly or quite four times as long as the basal stem of the cubital 



veiu 5. Aphantaphis. 



First cubital branch at most three times as long as the basal stem of the cubital vein. 

 First oblique veiu parting from the main vein at an angle of less than 55. 



6. Siplionophoroidee. 

 First oblique vein parting from the main vein at an angle of more than 70. 



7. Lithaphis. 



Cubital vein arising at half or more than half the distance from the first oblique vein to the stig- 

 matic vein. 



Main veins arising at nearly equal distances apart 8. Tephraphis. 



Main veins arising at distinctly unequal distances apart. 



Second oblique vein at base rarely so much as twice as uear the first oblique as the cubital 



vi- in y. Aphiiioji.ii- 



Srroud oblique vein a. I base four times as near the first oblique as the cubital veiu. 



The first, oblique vein straight, not two-thirds as long as the second oblique vein, and 



considerably divergent from it Id. Uri/flap/ii*. 



First oblique veiu curved out ward, nearly as long as the second oblique vein, anil 



hardly divergent from it 11. Sychnotrochua. 



Cubital vein once forked Sdlizoll<*lirilli. 



Cubital vein arising at. more than half the distance from the first oblique vein to the atiginatic 



vein '. 12. Scliizoeuroide. 



Cubital vein arising at less than half the distance from the first oblique vein to the stigmatic vein. 



Cubital vein Corking beyond the base of the stigmatic veiu 13. Amalcmchum. 



Cubital icin Corking before (lie base of the stigmatic vein. 



Base of second diseoid.-il cell less than three times the width of that of the first. 



14. AnconotuH. 

 Base of second discoidal cell more than five times the width of that of the first. 



15. Pterostigma. 



