ANT ACACIAS AND ACACIA ANTS OF MEXICO AND 



CENTRAL AMERICA. 



By W. E. Safford. 



[With 15 plates.] 



Among the plants of the New World which have attracted the 

 attention of earl} 7 explorers and naturalists are certain acacias 

 armed with large spines, which serve as nesting places for intrepid 

 little stinging ants. These spines, which occur in pairs joined at 

 the base, bear a resemblance to the horns of animals, some of them 

 to the spreading or incurved horns of oxen or buffaloes, others to 

 the erect horns of certain antelopes, while others, sometimes 

 curiously twisted, suggest those of an ibex. From the base of each 

 pair of spines at the median point grows a bipinnate lacy fernlike 

 leaf, which at length falls off, leaving the branches and stems 

 of the acacias studded with the persistent thorns. These leaves bear 

 on their petiole or main stem one or more glands, which when young 

 secrete nectar, often in such abundance that it drops to the ground ; 

 and on the tips of many of the leaflets small waxy bodies resembling 

 microscopic eggs or pears, which abound in oil and protoplasm. 

 On plate 2 is shown a leaf of Acacia comigera from a plant growing 

 in one of the greenhouses of the United States Department of Agri- 

 culture, bearing on its petiole an elongated nectar-gland and on its 

 leaflets numerous apical bodies. Both the nectar secreted by the 

 glands and the apical bodies on the leaflets furnish the ants with 

 nutritious food and are fed by them to their larvse cradled in the 

 hollow thorns of the plant. When the bush is jarred or shaken the 

 ants come swarming out furiously to attack the intruder with their 

 stings. Certain writers hold the theory that these plants, com- 

 monly called bull-horn acacias, have been able to enlist the ants as 

 a body guard, furnishing them quarters -and subsistence, in return 

 for their protection against leaf-cutting ants and other enemies, and 

 the plants have accordingly been called myr?necophilous, or " ant- 

 loving." Others refuse to accept this view, declaring that the 



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