42 BULLETIN 903, IT. S. DEPARTMENT OF AGRICULTURE. 



of the exposed portions of roots were surrounded by an inch of fine 

 sand, and all inoculations were made on these exposed portions, it 

 frequently happened that phylloxera? found their way to the unex- 

 posed portions, so that in the winter following the inoculations 

 hibernants were found in both the exposed and unexposed portions. 



The temperatures in the cages differed but slightly from those re- 

 corded simultaneously 2 feet below the soil surface in the laboratory 

 vineyard. In 1913-14 in midwinter, however, the former touched a 

 mark about 10° F. lower, besides being uniformly lower throughout 

 December and January in both the seasons 1913-14 and 1914-15. 

 During the period (August to November) in which the phylloxera? 

 entered hibernation there was no appreciable difference, and before 

 the commencement of the spring growth of the hibernants the tem- 

 peratures were again equalized. Thus, in the periods of entering 

 into and awakening from hibernation, vineyard conditions were 

 reproduced in the cages as far as temperature was concerned. Con- 

 temporaneous vineyard observations show that the behavior of the 

 hibernants on living vines in the cages simulated closely the be- 

 havior of those in the vineyards in the locality, and the habit of 

 clustering was often noted. The aphids entered into hibernation 

 and showed spring activity much as they did in the vineyards, but 

 in each phenomenon there was an exception. In 1914, six aphids 

 out of a lot of nine individuals hatching between August 24 and 26 

 proceeded to hibernate. Such early hibernation with succulent food 

 present is quite unusual in the field. Again, in 1914, on another vine, 

 part of a series of hibernants cast their skins as early as February 

 23, indicating that growth commenced not later than February 15. 

 In the vineyard, even upon warm soils, the first date; of activity was 

 never earlier than February 25. This early spring activity in the 

 cages was possibly due to comparatively high temperatures in Feb- 

 ruary, this being the only month during which the cage temperatures 

 exceeded those in the soil. 



Hihernation on American resistant and nonresistant vines in cages, 

 191Jf~15. — Along with the vinifera vines planted in the special cages 

 for observing the phylloxera? on living roots, a number of American 

 resistant and nonresistant vines were used for similar observation. 

 The nonresistant varieties (propagated from Vitis labrusca and V. 

 aestivalis) were Catawba, Isabella, Lenoir, Delaware, and Champion. 

 The Muscadine (V. votundifoT'ia) was used also. The resistant 

 hybrids, some of which were grafted to vinifera?, comprised Mour- 

 vedre X Rupestris 1202, Solonis X Riparia 1616, Berlandieri X Ripa- 

 ria 157.11, Riparia X Rupestris X Aestivalis X Monticola 554.5, 

 Aramon Rupestris Ganzin 1, Riparia Gloire de Montpelier, Rupes- 

 tris St. George. These vines were planted in the spring of 1914 and 

 inoculated thereafter. 



