PLANT LICE. > 159 
the principal vine districts of southern Europe, extending also 
into Algeria and through southern Russia into the adjoining 
countries of Asia. It has also been carried to New Zealand and 
South Africa. In this country it was at first known only in 
the region east of the Rocky Mountains, but was soon after 
found in California, where, however, it is confined practically 
to the vine districts of the Napa and Sonoma valleys. 
“Life History and Habits. The life cycle of the phylloxera 
is a complicated one. It occurs in four forms in the following 
order: The leaf-gall form (gallicola), the root or destructive 
form (radicicola), the winged or colonizing form, and the sexual 
form. The leaf-gall insect produces from 500 to 600 eggs for 
Fic. 143c—a, migrating stage, winged adult: b, pupa of same, lateral view; c, 
mouth parts with thread-like sucking sete removed from sheath; d and e, 
eggs showing characteristic sculpturing—all enlarged. After Marlatt, Div. of 
Entomology, Dep. of Agriculture. 
each individual, the root-inhabiting ansect not much above 100 
eggs, the winged insect from 3 to 8, and the last sexed insect 
but 1 egg. This last is the winter egg and may be taken as a 
starting point of the life cycle. It is laid in the fall on old wood, 
and hatches, the spring following, into a louse, which goes at 
once to a young leaf, in the upper surface of which it plants 
its beak. The sucking and irritation soon cause a depression 
to form about the young louse, which grows into a gall pro- 
jecting on the lower side of the leaf. In about fifteen days 
