Honey-Producing Caterpillars. 135 



when they are instantly withdrawn. The ants pay no heed 

 to the tubes. They seek for nothing from them, and expect 

 nothing. But they turn at once to the eleventh, caress the 

 back of that segment, and, putting their mouths to its open- 

 ing, exhibit an eager desire and expectancy. Suddenly a 

 dull green, fleshy, mammilloid organ protrudes, and from the 

 summit of which comes a tiny drop of clear green fluid, 

 which the ants, some two or three perhaps standing about 

 it, lap greedily up. As the drop disappears, this organ sinks 

 in at the apex, and is so withdrawn. The ants then run 

 about, some in quest of other larvae upon the same stem, 

 some with no definite object, but presently return and pursue 

 the caressings as before. The intervals between the appear- 

 ance of the globule vary with the condition of the larva. 

 Where exhaustion by long-continued solicitings occurs, some 

 minutes elapse before renewal is effected, the tubes in the 

 meantime remaining concealed. Fresh larvae, however, require 

 little or no urging, and globule follows globule, as many as 

 six emissions in seventy-five seconds, without even a retract- 

 ing of the organ. Often the presence of the ant, when the 

 larva is aware of it, evokes, all unsought, the sugary fluid. 



Ordinarily the tubes expand when the ants are absent from 

 the last segments, and are certainly withdrawn when they 

 come near. These tubes, from all appearances, serve as 

 signals to the ants. When the latter discover them expanded, 

 they know that a refection is ready, and rush to the opening 

 in the eleventh segment where it is to be found. The tubes 

 certainly serve no other purpose. No visible duct appears 

 in the dome of the tube when largely magnified, and the ants 

 seek nothing from it or the twelfth segment. They cannot be 

 used to intimidate, or to frighten away enemies, for in the 

 younger stages, when the larvae have the most to dread, 

 neither the tube nor the organ in the eleventh segment is 

 available. The outward openings, and the orifice in the 

 eleventh segment, exist in the youngest larval stages, but are 

 functionless until the larva has nearly attained maturity. 



