39^ Bulletin American Museum of Natural History. [Vol. XXI, 



behavior of ants with mines already constructed, when the root aphis 

 is offered to them. We have repeatedly performed the experiment 

 of starting colonies of ants on hills of corn in the insectary and ex- 

 posing root lice from the field to their attentions, and in every such 

 instance, if the colony was well established, the helpless insects have 

 been seized by the ants, often almost instantly, and conveyed under- 

 ground, where we would later find them feeding and breeding on the 

 roots of the corn. In many cases in the field, we have found the 

 young root aphis on sprouting weeds (especially pigeon-grass), which 

 have been sought out by the ants before the leaves had shown above the 

 ground; and, similarly, when the field is planted to corn, these ardent 

 explorers will frequently discover the sprouting kernel in the earth, and 

 mine along the starting stem and place the plant lice upon it. . . . 

 " I need hardly say that the relations above described between the 

 corn root aphis and these ants continue without cessation throughout 

 the year, the succeeding generations being quite as useful to the ants 

 as those whose history I have thought it worth while to follow in 

 detail. In order to determine more precisely the value of the services 

 performed by their guardians, I arranged in several years a series of 

 experiments designed to show to what extent the plant lice could 

 help themselves if left unattended. Owing to the waywardness of 

 the ants, which m most cases refused to content themselves in con- 

 finement, but one of these experiments came to a successful issue. 

 April 13, 1889, corn root aphis eggs were placed in the earth among 

 smart-weed roots to test the ability of the young lice hatching to 

 find the roots for themselves. A check experiment was started at 

 the same time with eggs placed in artificial cavities beside smart- 

 weed roots. April 25 no insects could be found on the plants of 

 the first experiment, while the cavities made in the second experi- 

 ment contained young lice upon the roots in fine condition." 



59. L. niger var. neoniger Emery. — This variety is characterized 

 by having erect hairs on the legs and antennal scapes. It is much 

 less abundant than the preceding and seems to have a northern or 

 subboreal distribution. A few specimens from Anglesea (Viereck) 

 and Hewitt (Davis) belong to this variety. 



60. L. brevicornis Emery. — I have taken this species at Fort Lee, 

 Halifax, Lakehurst, and near the Great Notch. It nests under 

 stones, on hill slopes and in pastures, in rather small colonies, culti- 

 vates root-aphids, and, so far as I have been able to observe, is 

 strictly subterranean like all of the remaining species of Lasiiis re- 

 corded in this list. The workers have a faintly pungent odor. 



