5 
become swollen and broken, and finally the outer portion decomposes 
and rots, and the roots ultimately die. With the multiplication of 
the root lice and their extension to all parts of the root system, the 
vine stops growing, the leaves become sickly and yellowish, and in 
the last stages the phylloxera disappears altogether from the decom- 
posed and rotting roots, and the cause of death is obscure to one not 
familiar with the insect. Many cases of death ascribed to drought, 
overbearing, winterkilling, etc., are undoubtedly due to the presence 
of the root louse. 
The abundance of galls on the leaves is not an indication of the 
presence of the root louse in any numbers, but, in fact, the reverse of 
this is usually true; while on the other hand the destructive abundance 
of the lice on the roots is often, if not usually, accompanied by little, 
if any, appearance of the leaf form. This is particularly noticeable 
with the European grapes, which are very susceptible to phylloxera 
and rapidly succumb to it, 
yet rarely show leaf galls. 
American grapes, on the 
contrary, are generally very 
resistant to the root form, 
and yet are especially sub- 
ject to the leaf-gall insect. 
Certain varieties, as the 
Clinton, which are most re- 
sistant to the former, are es- 
pecially subject to the latter. 
Distribution.—The phyl- 
loxera was carried to France ~ 
EOUiEIE59, Oh's90ted Amer ee a to ee 
ican vines, and has since  louse—much enlarged (original). 
spread through 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 com- 
vlicated 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 each individual, the root- 
inhabiting insect not much above 100 eggs, the winged insect from 3 
to 8, and the last or 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, 

