238 



Secondly, the fact that the plant-louse eggs hatch, as a rule, some 

 days in advance of the growth of corn in the fields (usually a week or 

 more before corn planting), and that in the meantime the lice are depend- 

 ent on young weeds in the earth, gave the hint for some starvation 

 experiments tried in two successive years. From these we learned that 

 young lice just hatched will perish within five days if deprived of food,, 

 whether attended by ants or not. It seems possible, consequently, 

 that their numbers might be greatly diminished in early spring by such, 

 a thorough stirring of the soil with disk harrows or other similar ap- 

 paratus, as would keep down the sprouting herbage in the cornfield. 

 Any treatment of the field the preceding summer or fall which should 

 diminish the number of seeds of pigeon grass or smartweed maturing 

 in the corn would diminish likewise the chances of survival of young 

 root lice the following year. I am told that these conditions are agri- 

 culturally manageable, and have arranged for field experiments to test 

 these methods. 



A simpler and perhaps more promising expedient is based upon the 

 care of the eggs of the common small brown ant, so frequently referred 

 to. The attention which these eggs receive both in winter and spring 

 makes it seem likely that the care of the ants is essential, and as these 

 insects become torpid early, rarely working beyond November 1, it 

 seems quite likely that late fall plowing of fields infested by them and 

 their guests, the root lice, to be followed possibly by harrowing, would so 

 break up their homes and scatter their treasures as to make it impos- 

 sible for the ants to reestablish themselves or to collect the plant-louse 

 eggs again. This supposition we shall presently test by treating in this, 

 manner a strip of land through an infested field and watching develop- 

 ments next spring. 



In conclusion, I ought to say that in reporting these results I am act- 

 ing only as the spokesman of the office, and that the main credit for the 

 work done and much of that for the selection of methods and the de- 

 vising of expedients should be distributed among Messrs. Garman, 

 Weed, Hart, Marten, and Mally, all of whom, while acting as my 

 assistants, have made important contributions to this subject. 



NOVEMBER 13.— AFTERNOON MEETING. 



Eighteen persons present. Dr. Eiley in the chair. 



The discussion on Mr. Forbes's paper was announced as in order. 



Mr. Howard asked whether Mr. Forbes considered the apple- louse 

 experiment a satisfactory piece of work. 



Mr. Forbes thought it satisfactory as far as it goes, but hesitated to 

 say that the negative was actually proven. Still the experiments were 

 many times repeated, in doors and out, for two years. 



Mr. Fletcher asked about the habits of the different broods of lice, 

 and asked Mr. Riley whether the hop-inhabiting forms of Phorodon 

 humuU, for instance, would live upon plum, if placed there artificially. 



