APHIDS INJURIOUS TO ORCHARD FRUITS. 19 



in this bulletin. The more common forms upon pear are the green 

 apple aphis, the oat aphis, and the clover aphis. 



Anotlier species, the Avoolly thorn aphis ^ is common in some local- 

 ities. Both winged and wingless forms are covered with a white 

 waxy substance. The wingless forms are pale green and the winged 

 forms have a black head and body. The insects hatch in the early 

 spring and soon attack the leaves, curling and twisting them. Dur- 

 ing early summer the winged forms leave the pear tree. In the fall 

 migrants may be found again, and these produce the sexual forms, 

 the females of which lay their eggs upon the bark. Besides pear, this 

 species occurs upon thorn, quince, and Juneberry. 



Two other forms are found commonly upon pear, but these occur 

 upon the roots, and since they are seldom found npon the branches 

 and foliage and require different remedial measures, they are not 

 ti'eated in this bulletin. The first of these is the woolly pear aphis,^ 

 which is common in the western part of the country, and the second 

 is Fitch's pear root aphis,^ which is very similar to the woolly thorn 

 aphis and occurs in the eastern United States. 



PLUM APHIDS. 



Three or four species of aphids are common on the plum, two of 

 which are, during some seasons, A-ery injurious. Many complaints 

 of injury to Japanese and native plums by the rusty plum aphis have 

 come from the more southern States, while the mealy plum aphis is 

 more often prevalent in the North and West, on Domestica, or the 

 European type of plums. The hop aphis, according to records of the 

 Bureau of Entomology, has not occasioned much injury to plums in 

 recent years, although in the Pacific Northwest it continues to be a 

 pest of importance to hops. 



THE RUSTY PLUM APHIS.* 



The rusty plum aphis was discovered and named from individuals 

 feeding on grass, but is better known by its injuries to plums. It is 

 rusty brown or deep purplish, with Avhite bands upon the legs. 



This species feeds upon the tender twigs and foliage of the plum 

 and also upon the peach. The first stem-mothers attack the buds 

 just as they are expanding in the spring and later crawl down among 

 the opening leaves. As the season advances whole twigs or small 

 branches may be literally crowded with the aphids (fig. 15), and such 

 twigs usually die. Another species, not yet named, also has this 

 habit, and this form may be very injurious to the twigs, as it remains 

 on the plum throughout the summer. 



^ Prociphiliis cornirjatans (Sirrine). '^ Prociphtlus pyri (Fitch). 



' Eriosoma pyricola B. & D. *Aphis eetariae Thos. 



