84 



has crawled quite a distance. The egg-shells or pellicles are left as an 

 almost transparent round dot at the place of hatching. Nearly all the 

 substance of the egg seems to be absorbed into the young aphis. In- 

 serted a bit of fresh youug leaf, but they do not seem to be attracted to 

 it, and remain crawling on the glass. 



August 23. — Two more have hatched. They appear all alike so far as 

 can be ascertained with a lens. Three were sacrificed for microscopic 

 examination. Have the specimens under almost constant observation, 

 but am not able to find them pairiug or exhibiting any sexual attrac- 

 tion. Neither can I induce them to feed on even the teuderest bits of 

 leaf. They appear precisely like the parthenogenetic forms through 

 my lens, which is not sufficiently powerful to resolve the mouth parts 

 and genitalia. 



September 1. — Only two still alive and no eggs. Transferred the sur- 

 vivors as carefully as possible to fresh leaf and placed in clean tube. 



Examined inclosed leaves out of doors but could detect neither eggs 

 nor larvre. It is an almost impossible task to keep track of such micro- 

 scopic creatures in the open air. 



The wingless lice have now become quite abundant on all our post- 

 oaks. I do not find them on the white oak proper, but as I have ex- 

 amined them almost daily since the middle of July I am confident that 

 none of the winged individuals occurred on any of the oaks on the 

 place. I believe they never do occur in any numbers except on the 

 more succulent growth of sprouts where living trees have been cut. 



September 10. — All my progeny of winged lice have perished without 

 leaving a single egg. Made another excursion into the country but 

 obtained only two or three winged individuals which I put in tube, but 

 of which I do not entertain much hope. 



On one of the leaves out of doors, isolated about a month ago, I find by 

 critical examination a very few minute specimens which are probably 

 the progeny of the winged forms inclosed. Put some in balsam, though 

 I can not see that they differ from the other wingless young on exposed 

 leaves. 



September 15.— No success with the last inclosure in tube. 

 October 25. — Have had one or two quite hard frosts. Leaves all 

 turned in color, and Phylloxera becoming very active, congregating 

 along principal veins and migrating on to the twigs. Their insect ene- 

 mies have mostly disappeared and I notice that eggs are more plentiful 

 than usual on the leaves. 



From my observations this year I incline to the opinion that the 

 winged form is necessary merely for the spread of the species, and that 

 the young from the eggs of this form are not necessarily true-sexed 

 individuals, although it is possible that these may occur without any 

 especial regularity from the eggs of both winged and wingless forms. 

 Another year, if nothing happens to prevent, I will try to have some 

 oaks in flower pots for more convenient and natural colonization of the 

 Phylloxera, and for greater ease in examination. 



