84 



THE MONTHLY BULLETIN. 



THE COMMON COTTONWOOD LOUSE. 



Thoinasiu popuUcoIa (Tlios.). 



General Appearance.— The adults are dark red or wine colored, 

 many appearing- nearly black and are distingnished from other poplar 

 lice by the clouded wings. The winged forms are nuich darker than 

 the apterous, which are distinctly robust and are characterized by a 

 yellow blotch on the back, not unlilce an inverted "Y." This species 

 clusters in great colonies at the terminals of young shoots. 



Life History. — So far as known the entire life cycle is passed upon 

 Cottonwood trees. During the early summer months the young shoots 

 of the host plants are seriously attacked, but by fall all entirely dis- 

 appear. It is not known how the winter is spent. 



Distribution. — Throughout the entire State wherever the food plants 



grow 



Food Plants. — The common cottonwood {Populus trichocarpa) and 

 poplar are invariably infested by this louse. 



Natural Enemies. — Though this pest does considerable damage to 

 young growth during the summer months, it is finally checked by 

 many natural enemies, chief of which is the native ladybird, Seym » us 

 nehulosKS. 



THE HOP LOUSE. 



Phorodon humuU Schrauk. 

 (Fig. 66.) 



General Appearance. — The wingless lice are pale yellowish-green; 

 the winged lice being of the same general color with 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 louse. The over-wintering eggs are laid upon the 



fruit trees in the fall. The 

 spring broods breed and 

 feed upon the leaves 

 until the hops begin to 

 appear. By this time 

 winged forms occur in 

 large numbers and these 

 migrate to the hop fields 

 where the summer is spent. 

 The young plants and foliage 

 of the hop vines are severely 

 damaged by this pest, so as to completely ruin portions of the fields. 

 In the fall, migrants again return to the fruit trees, and give birth 

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

 sexual forms occur in the hop fields while the lice may be found upon 

 the plum trees during the summer, so in all probability they can exist 

 upon either of these hosts through the season. 



Fig. 66. — Winged nnd apterous females 

 of tlie hop louse, Phorodon humuli Schrank. 

 (After Riley.) 



