1912] Mann — Parabiosis in Brazilian Ants 39 



species should have become arboreal in a region where so many 

 animals have taken up this habit. 



I admit that the finding of one example is not conclusive evi- 

 dence of regular parabiotic association, but the observations here 

 recorded seem to indicate a much closer relation than that of Doli- 

 choderus and Cremastogaster, for it is evident that both species 

 would derive benefit from the association. In the earthy, arbo- 

 real nest of Dolichoderus, Odontomachus finds a condition similar 

 to that of the ordinary nesting place of the genus, while to the 

 other, a feeble species, the advantage in having a colony of power- 

 ful stinging ants in the same nest is obvious, provided of course 

 that it, itself, is not molested. For the reasons stated above, I 

 do not believe that such molestation occurs. 



The difference in the stimulus necessary to bring each species 

 out of the nest is interesting. Dolichoderus sallied out at a slight 

 disturbance, Odontomachus not until the nest was more thoroughly 

 jarred and prodded. Ordinarily the smaller ant would be able 

 to combat a feeble enemy, while one capable of seriously disar- 

 ranging the nest would excite the more powerful nest-mate. This 

 difference of habit was observed a number of times in the same 

 nest. 



As both of the forms of Dolichoderus and Odontomachus are 

 new to science, I append a description of the worker of the latter 

 and of all the phases of the former. 



Odontomachus afiinis Guerin, subsp. tnayi subsp. nov. 



Worker. Length 9.5 mm. Head, excluding mandibles, 1^ times as long as 

 broad. Mandibles f length of head; inner edge with twelve fine teeth; apex with 

 three large teeth, the most apical long and pointed, the most basal nearly as 

 long, but sharply truncate; between these, closest to the most apical and one half 

 as long as this is a smaller tooth. Thorax as in affinis, but sculpture on pronotum 

 is longitudinally oblique. Petiolar node short and thick, spine slender, acuminate. 



Head shining, finely punctate. Thorax opaque; pronotal sculpture strong, 

 cencentric, on disc longitudinally oblique, diverging from the median impression. 

 Abdomen smooth, shining. 



Head with fine short, recumbent pubescence; vertex in front with two long hairs. 

 Pronotum above with several long erect hairs. Abdomen with erect pile and re- 

 cumbent pubescence. Coxae and base of posterior border of femora with long 

 hairs. Legs finely pubescent. Pubescence and pile pale yellow in color. 



Color rufo-testaceous, the apex of the abdomen in some specimens is slightly 

 darker. Mandibles fuscous. 



