90 



PROTECTION OF PLANTS, 1917-18 



Chermes floccus on white pine =Chermes tioccus on red and black 



spruce. 

 Chermes cooleyi on Blue and Engelmann = Chermes cooleyi on Douglas fir. 

 spruces. 



The Green Peach Aphis (Mysiis persicae Sulz.) showing also the venation of the wings 

 and the location of the antennae, cornicles and cauda. (After Essig.) 



APHIDIDAE (PLANT LICE OR APHIDS) 

 Chief Economic Genera. 



A. — Front wings with three discoidal veins; antennae generally 6-7 jointed. 



B. — Third discoidal vein of front wings twice forked (exception Toxoptera). 

 C. — Cauda long, antennae on distinct frontal tubercles. 

 D. — Third discoidal vein once branched. ^ro.ro/)/^ra. 

 DD. — ^Third discoidal twice branched. 



E. — Cornicles cylindrical or slightly tapering. 



F. — Frontal tubercules strongly gibbous on the inner side. 



— Myzus. ■ 

 FF. — Frontal tubercles with a long tooth on the inner 



side. — Phorodon. 

 FFF. — Frontal tubercles not or only slightly gibbous. — 

 Macrosiphiim. 

 EE. — Cornicles clavate at the tips. — Rhopalosiphum. 

 CC. — Cauda short and conical. Distinct frontal tubercles absent. — 

 D.— Cornicles clavate. — Hyadaphis {Siphocoryne). 

 DD. — Cornicles not clavate. 



. E. — Cornicles moderateh' long, longer than cauda, cylindrical. 

 Aphis. 



