h, '08) ENTOMOLOGICAL NEWS. 123 
| Me grape Phylloxera (Phylloxera vastatrix) produces an 
dance of winged individuals in Europe and elsewhere in 
-d States, but in California winged forms are extremely 
is possibly corresponds with the high ratio that soda 
bear to magnesium in our soils. 
ogg heal of this department, has suggested to me that 
¢ winged forms are produced on the finest roots near the 
fac eee oer | this State might be bet- 
ex i by the almost invariable destruction of such roots 
Pacy climate. 
¢ occasional production of broods of winged Phylloxera 
ee Semel rise and fall of alkali, 
x the ratio of the different salts near the surface of 
’ gro i, thus conforming to the chemical theory of wing 
foduction, or the explanation may be that a better moisture 
=. 2 on such years may permit sub-surface rootlets to live 
if enough to produce a brood of winged individuals The 
son for the development of winged forms on these upper 
otlet may be according to the second explanation, the slow 
ryin out of these parts or their periodical wilting during the 
ummer resulting in a condition comparable with that occur- 
now in our cabbage fields. 
r phenomena occur in this region in the case of num- 
bes oer specie of lant tec They increase until they 
ch a point where the leaf will be brought, by their combined 
at ck, to a semi-wilted condition, and then all the young sub- 
ze vent produced will develop wings. Whole trees are thus 
_ sometin freed from plant lice. 
ae i well known that wing-producing lice develop much more 
in y than those that remain wingless. The present sugges- 
is that a slower development, cither immediately before or 
birth, is the exciting cause of wing formation. 
“The foregoing is presented with the hope that eters wil 
t¢ observations, the coming season, of evidence of spontan- 
“cous wing production and its relation to dry periods or to 
excessive infestation of the plant. 
