THE GRAPE PHYLLOXERA IN CALIFORNIA. 



35 



FIXATION OF BEAK. 



To secure information regarding the fixation of the beak in the 

 root five lots of hibernants were examined on January 23, 1914. 

 The results are given below. 



Table II. — Fixation of beak of hibernants of the grape phylloxera. 



Lot No. 



Number 

 of indi- 

 viduals. 



Number 

 with 

 beaks 

 fixed. 



Number 

 with 

 beaks 

 free. 



Remarks. 



1 



25 

 25 



25 

 25 

 20 



12 

 24 



16 

 22 

 8 



IS 

 1 



9 

 3 



12 



"Under 2 layers of bark on large root. 



2 



Large root"; insects originally under 2 layers of bark, 



3 



but layers peeled off some time before experiment. 

 Small root; insects on tuberosities. 



4 



Do. 



5 



Under several lavers of bark on stock of vine 3 inches 





below soil surface. 



Total 



120 



82 



38 





In lots 1, 2, and 5 the individuals that had their beaks fixed in the 

 roots were obviously the more healthy. In lots 3 and 4 all the 

 phylloxera? appeared equally healthy. They were on more succulent 

 roots than those in lots 1, 2, and 5, and it may be that on such succu- 

 lent food the hibernants have a habit of driving in and drawing out 

 their beaks at will, whereas on harder roots this would not be pos- 

 sible. It is evident that hibernants situated on the outside bark of a 

 root are likely to be washed off by water if their beaks are not in- 

 serted into the root. The experiment would serve to indicate that in 

 the individuals of lots 1 and 5, wherein the hibernants were protected 

 under layers of bark, the majority had their beaks free, while in lots 

 2, 3, and 4, wherein the hibernants were exposed, the majority had 

 their beaks inserted, so that it appears that the fixation of the beak 

 acts as an anchorage. 



NOURISHMENT. 



t The hibernant larva partakes of nourishment very slightly, if at 

 all, before it settles for the winter. During the period of true 

 hibernation it apparently takes no nourishment. Therefore it is 

 probable that the great majority of the hibernants take their first 

 food when they arouse themselves from their lethargy in spring. Of 

 those observed to feed before hibernating, a few pass one or rarely 

 two molts, while the rest remain unmolted but larger in size than the 

 true hibernating larva. The writers have observed instances in 

 which severed pieces of roots infested by hibernants formed winter 

 lesions, the presence of the beaks in the root affording a stimulus. 



