Do Ants Kill Trees About Their Colonies? 



By R. C. Hawley and S. J. Record 



DURING the past few years the writers have had 

 occasion to note the death of young trees in the 

 vicinity of ant hills. As the type of injury is 

 practically the same in every case, and has never been 

 found except in association with ant colonies, it is as- 

 sumed that the ants are responsible, directly or indirectly, 

 for the damage. Observations have been made on more 



than sixty ant hills about New Haven, Ansonia, Middle- 

 bury, Union and other parts of Connecticut and in Pike 

 County, Pennsylvania. The same trouble has been re- 

 ported from other portions of Pennsylvania, Massachu- 

 setts, New Hampshire and New York. 



The insect in question was, in all cases but one, the 

 mound-building red ant, Formica exsectoides Forel. The 



KILLED BY ANTS 



Section through a young white pine showing gird- 

 ling due to the ants and continued growth above 

 it. Most of the dead bark covering the injured 

 portion was broken off in handling specimen. 



FORTY TREE CASUALTIES AROUND AN ANT HILL 



Around the ant hill seen in the photograph, and located near New Haven, Connecticut, forty white 

 pine trees have been killed or injured. 



apparent exception was one low, flat mound in which the only ants observed 

 were the common black, Formica fusca Linn. var. subsericca Say. Since, 

 however, the red ant is parasitic an the black, it is not improbable that even 

 in this case the red ant was responsible for the damage done. This view is 

 strengthened by the fact that inspection of a considerable number of other 

 black ant nests has revealed none of the characteristic injury to tree growth. 

 In a few cases colonies of a dark-colored aphid tended by ants were found 

 on trees near the red ant nests. 



Most of the damage noted has been to white pine (Pinus strobus), from 

 a few to fifteen years of age. Other species observed by the writers to have 

 been affected were Scotch pine {Pinus sylvestris), red cedar (Juniperus 

 virginiana), American aspen (Populus trcmuloides), shag-bark hickory 

 (Hicoria ovata), gray birch (Betula populifolio), Bear oak (Quercus 

 nana), and Staghorn sumach (Rhus hirta). The effects are most noticeable 

 in pine plantations and in openings in the high forest where young trees 

 are coming in. 



The areas of infection are irregularly circular, and the radius within which 

 trees are damaged about each ant hill is subject to considerable variation, 

 reaching a maximum of 25 feet, with an average possibly of about 10 feet. 

 The largest number of trees noted, killed or attacked about a single colony, 

 was 40. Where ants are abundant the loss may be very considerable. In one 

 white pine plantation of about a quarter acre near Union, Connecticut, fully 



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