29 



The following observation bears upon the relation of the root and 

 aerial forms to each other. On the 25th of June a number of the 

 root form were colonized on the roots of corn growing in the labor- 

 atory, and on the 5th of July one of these lice was observed to have 

 estabhshed itself u^jon one of the leaves. On the 6th of July it was 

 found to have given birth to two young during the preceding night. 

 Others of the root lice were observed upon the leaves, but the plant 

 at this stage began to die, and the experiment ended. I have little 

 doubt, however, that this would have proved the beginning of a 

 colony of aerial corn lice. 



In the light of these observations, the history of the lice during 

 the year seems to be this : Eeproduction is carried on during the 

 warm months by the viviparous (mostly wingless) females of the 

 aerial form. In the fall viviparous winged females predominate, 

 serving to distribute the species and (generally) by hibernating pass 

 it over the winter months. In the spring these females resort to the 

 roots and bases of the stems, where they are then protected from 

 the cold, and multiply here until the warm weather of the latter 

 half of July sets in, when their descendants migrate to the leaves, 

 husks and silks, founding there the colonies of aerial lice. 



An account of the life history of this plant louse would be imper- 

 fect without some notice of the little ant, Lasius flavus. In the spring 

 this ant is almost invariably to be found with the root lice, carefully 

 guarding the latter, and when the burrows are exposed carrying them 

 away and concealing them in the earth. During the £ore part of 

 summer it occurs on the plants among the aerial lice, but when the 

 dry season of late August and early September sets in, it burrows 

 deep into the earth and is not often seen except after rains, when 

 it opens up its burrows. With the fall rains it again comes to the 

 surface and may be found to the end of the season with its young 

 and colonies of Schizoneura ixinicola on the roots of grasses. Its 

 purpose in attending the corn louse is doubtless to secure the sweet 

 fluid which a tap from an antenna will cause a full fed louse to 

 eject.* But I am disposed to believe that the ants attend Schizo- 

 neura panicola for the purpose of browsing upon the waxen coat 

 which covers that species. I have several times seen the ants gath- 

 ered about a detached mass of this wax and apparently eating it. 

 In some nests of these ants one finds in winter masses of plant lice 

 eggs which have been collected the previous fall. The ants carry 

 these about as the do the plant lice. Why they are collected, I am 

 unable to say. A natural inference is that they collect them to stock 

 plants in the vicinity of their nests in the spring.! It may be they 

 are used as food, as, indeed, from the results of some experiments 

 in keeping them indoors I suspect the lice are occasionally. 



* During the past summer I have repeatedly seen the ants secure this favor, and to 

 my surprise the sweet droplet was always discharged from the vent, never from the 

 cornicles. 



+ A quantity of these eggs were collected last spring and given to a colony of ants 

 kept in doors. They hatched small green plant lice which at once scattered in all di- 

 rections. They would not make their home on any of the plants offered them, and so 

 were lost. 



