i6o 



AN INTRODUCTION TO ENTOMOLOGY. 



bers. The mature lice measure 2 mm. (0.08 inch) in length. They 

 are oval, of a dull white color, with dusky legs and antennae, and 

 with the body dusted over with a white powder. 



Other species of this sub-family are found on roots of grasses or 

 herbaceous plants, and usually accompanied by ants. 



Sub-Family II. — Chermesinjl* 

 The CJiermcsinee includes those genera of plant-lice in which the 

 front wings have only two discoidal veins ; the antennae are from 

 three- to five-jointed. 



This sub-family is represented by two common genera, Chermes 

 and Phylloxera. In Chermes the antennae are five-jointed, while in 

 Phylloxera they are only three-jointed. 



Chermes. — The most common species of this genus is the Pine 

 Blight, Chermes pinicorticis. This, in its most conspicuous form, ap- 

 pears as patches of white, flocculent, down-like matter on the smooth 

 bark of young white-pine trees. Beneath these patches of white 

 substance the very minute young lice can be found. The winged 

 generation appears in early summer. A closely allied species, Cher- 

 mes abietieoleiis, infests the terminal shoots of spruce, producing 

 large swellings. 



Phylloxera. — This genus contains many species ; one of them, 



Phylloxera vastatrix, has 

 attracted so much atten- 

 tion by the great extent 

 of its ravages that it is 

 often referred to as the Phyl- 

 loxera. It is more properly 

 termed the Grape Phyllox- 

 era. We have space for only 

 a brief account of the his- 

 tory of this species. 



The presence of this in- 

 sect is manifested by the 

 vines in two ways : first, in 

 the case of certain species of 

 grapes, there appear upon 

 the lower surface of the 

 leaves fleshy swellings, which are more or less wrinkled and hairy 

 (, Fig. 134); these are hollow galls, opening upon the upper surface 



Fig. 134. — Leaf of grape with galls of Phylloxera. 

 (From Riley.) 



* Chermeslnae, Chermes: Arab, kermes, Skt. krimi, a worm. 



