S6 BTJUJETIH 903, T. S. DEPAETMEST: OP AGEItTO LTUiffi . 



other deposited two eg^rs. on September 28 and 29, respectively. 

 These hatched in 11 days, the resultant larva? obviously being 

 radicicoles but surviving only a few days. The third individual 

 matured November 1. and between this date and November 10 it 

 deposited 10 eggs. After this it became weak, and on November 16 

 was mounted on a slide. The eggs were exactly similar to those laid 

 by wingless radicicoles. and two of them measured, respectively. 

 0.310 by 0.166 mm. and 0.297 by 0.168 mm. Seven eggs were trans- 

 ferred for observation to another root, and three eggs hatched in 

 from 11 to 16 days, the resultant larvae settling down for hibernation. 

 One of these soon died, but the other two passed the winter in due 

 form, and matured in April. 1916. Both of them were typical 

 radicicoles and subsequently deposited many eggs. 



In Italy Grassi and his assistants found that the great majority 

 of the intermediates were parthenogenetic. but one individual was 

 found to contain a sexed egg. In discussing the phenomenon of the 

 intermediates, they gave it as their opinion that the parthenogenetic 

 individuals were those which up to their third stage were destined 

 to become radicicoles. but in that stage changed their development 

 to that of winged migrants, while the character of their eggs had 

 been already fixed before the change and so remained parthenogene- 

 tic. In the case of sexuparous intermediates the change was made 

 in the reverse direction, the larva? at first being destined to become 

 migrants and. therefore, when they matured as nymphicals they 

 deposited sexed eggs. 



In California the recorded eggs laid by nymphicals were all par- 

 thenogenetic. but the possibility of some of such eggs being sexual is 

 not entirely excluded, in the writers' opinion. 



The nymphicals do not leave the roots in the manner of the 

 winged insects, and therefore deposit their ova on the roots. In the 

 case of sexuparous nymphicals. the sexes and winter egg would 

 presumably develop underground. Whether in California such a 

 development occurs or not can not be stated from our present knowl- 

 edge, but in view of the fact that for many years the leaf galls have 

 been unknown, it appears certain that such a cycle proceed- no 

 further than the winter egg. 



DEPOSITION OF THE SEXUAL EGGS. 



The migrants deposit eggs (Pi. Till. /. //. i) which are of two 

 kinds, viz. male and female, and from these eggs issue the true sexual 

 aphids. Sexual eggs have never been found by the writers in the 

 vineyard, either on vinifera? or on resistant vines, although a large 

 number of vines have been examined. In laboratory experiments a 

 large number of sexed eggs have been produced. Considerable dis- 

 cussion has taken place among European writers as to the normal 



