Life History of certain Little-knouii Aplddidw. 209 



lice were found abundant under the care of the ants on the 

 younof sprouts of Setaria and Polygonum. The following day 

 a part of the field was plowed and larval aphides were found 

 again in the nests of Lasius. On May 6, in a part of the field 

 not yet plowed, half-grown specimens were found in an ant's 

 nest. By May 21 the lice had been mostly transferred from 

 the Setaria and smartweed to the young corn roots. Some 

 stem-mothers were yet present, and a few wingless adults of 

 the second generation were seen, but the great majority of the 

 lice were the young of this latter form (i. e., those born from 

 the stem-mothers). Two days later a large number of these 

 had become adult, some of them winged but most wingless, 

 and a large number of pupte of the winged form were present, 

 as were also a few stem-mothers. At this time the ants were 

 mining about the corn plants all over the field, evidently pre- 

 paring for the reception of the winged migrants, but as yet 

 very few of these mined hills contained lice. June 1 all stages 

 of the second and third generations were common throughout 

 the field, many of the specimens being winged. On the 27th 

 of the same month, however, only wingless adults and larvae 

 were found. No further observations were made in this field 

 until October 10, when both wingless viviparous and oviparous 

 forms were abundant, the most of the lice being young of the 

 oviparous form. A week later the oviparous adults were most 

 abundant, and the viviparous ones were scarce. Many of the 

 oviparous adults were wandering around among the Lasius 

 galleries apparently unmolested by the ants, which behaved 

 very differently toward them from the way they act toward 

 the viviparous forms earlier in the season. I watched repeat- 

 edly to see the ants pick one of the oviparous lice up when the 

 nest was disturbed, but without success. In large ant colonies 

 the oviparous forms had often wandered some distance from 

 the corn roots. 



In a field, as yet unplowed, that had been in corn the year 

 previous I found (April 30) two separate masses of plant louse 

 eggs in one nest of Lasius alienus. Many of the eggs had 

 evidently already hatched, for there were numbers of young 

 lice on the sprouting Setaria and smartweed. 



