102 INJURIOUS AND BENEFICIAL INSECTS OF CALIFORNIA. 



THE HOP APHIS 



Phorodon hamuli (Schrank) 



(Aphis foumuli Schrank) 



Description. — The wingless viviparous female is pale yellowish - 

 green and the winged form is the same general color with the head, 

 dorsum of the mesothorax and spots on the abdomen dark. 



Life History. — The life history of this louse greatly resembles that 

 of the mealy plum plant louse. The over-wintering eggs are laid 

 upon the plum trees in the fall. The spring broods feed upon the 

 leaves and give birth to new broods until the hops begin to appear. 

 By this time winged migrants appear in large numbers and these 

 migrate to the hop fields where they live during the summer. The 

 young plants and foliage of the hop vines are severely damaged 

 by this pest, which may completely ruin portions of the crop. In 

 the fall, migrants return to the plum trees, and give birth to the 

 sexual forms which produce the over-wintering eggs. The sexual 

 forms occur also in the hop fields, while the different stages may be 

 found upon the plum trees during the summer, so in all probability 

 they can exist upon either of these hosts throughout the season. 



Distribution. — This species is very common and destructive, espe- 

 cially in the central hop-growing districts of the State. 



Food Plants. — This is primarily a hop pest and is certainly one 

 of the worst enemies of that crop. It also feeds upon plum trees, 

 occurring upon either hops or plums throughout the summer. 



THE LUPINE APHIS 66 



Macrosiphum albifrons Essig 



(Fig. 83) 



Description. — This is a large green louse, completely covered with 

 fine white powder or pulverulence, which makes it appear silvery- 

 gray. The length varies from £ to }■ inch. 



Life History. — The lice appear in the spring, soon after the lupines 

 are well started and are especially abundant about flowering time. 

 The younger shoots and especially the flowering tips are attacked, 

 and many lice continue to work upon the green seed-pods. The 

 species collects in large colonies and works great havoc to the hosts. 



Distribution. — This species occurs in many parts of the State. 



Food Plant.— The lice attack the wild lupine (Lupinus albifrons). 



Natural Enemies. — The writer has reared a large undetermined 

 internal parasite from this aphis. 



60 W M. Davidson reports a species very much like this, if not the same, attacking 

 •egetables and lupines in the San Francisco Bay Region. 



