WINE-MAKING IN CALIFORNIA. 53 



PUPA FORM. 



Much interest attaches to this form, since it is through it 

 that we know the conditions which will produce the winged 

 form. The later is found with great difficulty upon the vine, 

 while the former is readily distinguished among its associates, 

 the common root louse or larva, which is first sought after in 

 the examination of an infested vineyard. The pupae once 

 found, it becomes easy to trace them to the winged form, 

 which is usually near by. 



Conditions Governing the Production of Pupce. My first 

 observations on the fertile winged form were made on speci- 

 mens accidently produced in the laboratory. By tracing back 

 to its origin the root upon which these first individuals were 

 found, the needful conditions and surroundings could be de- 

 termined, and thus the winged form could be sought for 

 more intelligently, and found in greater Tiumbers. As before 

 noted, the small, soft, fibrous rootlets of the current year's 

 growth had seemed to be most productive of the form from 

 which the winged insect is developed. 



Movements and Transformation of the Pupa Form, The 

 movements of pupa, or wing-pad insect, observed chiefly 

 during 1884, were not found to be altogether along the 

 smaller roots, and thence up the main body to the crown of 

 the root, as is usually supposed, but the insects frequently 

 left the roots and passed up through the soil, which in no 

 place was less than three inches deep. This movement af- 

 forded an excellent opportunity for determining where the 

 transformation into the winged form takes place. 



The insect in various stages of development could be 

 found in the earth from the surface to the roots, the most in- 

 complete forms being found deepest below the surface of the 

 ground. Some were found under stones, and in such posi- 

 tions as to place it beyond a doubt that they passed through 

 the changes underground, and came to the surface in a trans- 



