THE GEAPE PHYLLOXERA IN CALIFORNIA. 
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are lemon yellow and oval. Upon hatching from the egg, the bright- 
yellow larva seeks food. Larvae hatching in spring mostly settle near 
the eggshells, but in summer and autumn a considerable percentage 
travel along the roots or forsake the vine altogether, either following 
cracks in the soil to reach neighboring vines or ascending to the sur- 
face of the soil and traversing the ground in their endeavors to reach 
other vines. To those that voluntarily forsake the vine has been 
given the term " wanderers." The larvae molt four times, and on the 
Fig. 10. — Diagram to illustrate annual life history : Innermost shaded crescent, active 
period of wandering radicicole larvae ; middle shaded crescent, period of development 
of the sexuparous migrant ; shaded portion of outer circle, hibernation period of 
radicicole larva? ; unshaded portion of outer circle, period of active life on the roots. 
completion of the final molt become mature insects. At first oval, 
they tend to become pyriform as they grow. The color, yellow, 
yellowish-green, or yellowish-brown, is dependent on the nature of 
the food. The length of the developmental period varies according 
to food and meteorological conditions. On succulent living roots 
the average period of larval development was found to be about 22 
days (hibernant generation excluded), and the maximum and mini- 
mum respectively 36 and 10 days. 
