— 176 — 



enclosed as to exclude insects from without and to prevent those within 

 from escaping- In this inclosed frame three hills of field corn were 

 planted, and on their appearance above ground one of them was stocked 

 with a colony of Lasius alienus Foist., the small ant which habitually at- 

 tends the root form of this plant-louse. The ants made themselves quar- 

 ters about the roots of the corn, and on the 19th of July a number of 

 wingless viviparous female lice with their young and one pupa were 

 place, 1 within reach of the ants and were at once carried to the roots of 

 the corn by the latter. On the 22(1 of July other root lice, wingless and 

 w>nged, were placed near the stocked plants and were also carried to the 

 ro its. With a view to learning whether or not root lice would of them- 

 selves make their way to the roots of corn, on July 221I, and subsequent- 

 ly, many specimens were placed at the base of one of the hills not col- 

 onized with ants. They always disappeared, but could not be found 

 afterwards on the roots. The plants with which they were placed con- 

 tinued to grow as well as the third hill under the cover which from the 

 first had not been disturbed, and at the close of the summer careful 

 search did not disclose lice on the roots. The injurious effect of the 

 lice on the infested plants was soon noticeable in their smaller size and 

 less vigorous growth. At various times during the summer the burrows 

 of the ants along the roots were uncovered, revealing each time the 

 presence of lice. From July 23rd until the first pf August winged lice 

 came from these burrows and were sometimes found on trie blades ol 

 corn but more frequently on the inside of the enclosing cloth of the 

 frame. These winged individuals showed no disposition to establish col- 

 onies on the blades of corn, but on the contrary seemed desirous of 

 leaving the plants as soon as possible. All were viviparous females and 

 in several cases confined upon the plants, although sometimes inserting 

 the beak and feeding, they died with the ovaries filled with young. The 

 migration of winged lice from the ground was observed at the same time 

 in neighboring fields where on the 27th of July many of these winged 

 lice, chiefly dead, were found on the blades. A careful search of the 

 roots made at the same time showed that the root form was now rare in 

 situations in which it had done most injury in the spring. Roo f lice 

 were observed on the enclosed corn until the latter part of August, but 

 were not again uncovered until October 7, the ants in the meantime 

 being constantly observed running in and out. On the morning of 

 October 7th, the infested plants were dug up carefully and carried in 

 doors for careful examination and upon one of the roots which had 

 several times during the season been found to support plant lice was 

 found a small colons of oviparous females, tne only egg-laying example 



