ORCHARD INSECTS 



307 



The Mealy Plum-louse * is a light green species covered 

 by a bluish-white mealy powder. It has a long narrow body 

 marked with three longitudinal stripes of a darker green. 

 The honey-tubes are short, thick, and slightly constricted at 

 the base. The aphides migrate to certain grasses upon 

 which they feed during the summer and return to the plum 

 or prune in the fall and there deposit their winter eggs. 



FIG. 221. The hop plant-louse. (After Riley, U. S. Dept. Agr.) 



Third generation on plum the generation which flies to the hop enlarged; 

 head below at right still more enlarged. 



The Hop Plant-louse f also passes the winter in the egg 

 stage on the plum and migrates to hops, which are often 

 seriously damaged. Only rarely is it sufficiently abundant 

 to do much injury to plum foliage. The wingless forms are 

 light green or yellowish-green with no distinctive markings, 

 while the winged forms have the head, thoracic lobes and a 

 few dashes on the abdomen black. The species may be 

 readily distinguished by the prominent tubercle which pro- 



* Hyalopterus arundinis Fab. f Phorodon humuli Schrank. 



