RELATIONS OF ANTS TO OTHER INSECTS. 35 * 



additional observations have been made by Baer (1903) in Argentina 

 and Green (1900) in Ceylon. l>aer saw Camponotus pnnctnlatus 

 attending Enchenopa fcrruginea. Green's observations relate to species 

 of Ccntrotus, some of which have a long, brightly colored anal tube. 

 He says that he has " watched the la r vie of various species of Ccntrotus 

 being assiduously attended by ants. The larvae are gregarious, fre- 

 quenting the succulent shoots of plants, and have an extensile organ at 

 the extremity of the body, from which the coveted fluid is emitted. 

 This organ is distinctly 3-segmented. In the species from which the 

 accompanying drawings were made [Fig. 212], the small terminal seg- 

 ment was of a crimson color ; the penultimate segment black, with a 

 broad white median band ; and the basal segment (of the extensile part ) 

 white. When the insect is undisturbed, the organ is withdrawn into 

 the long conical segment which apparently terminates the body, but is 

 extended immediately upon application by the attendant ants." I have 

 repeatedly seen whole colonies of Formica obscuripes, ciliata and orcas 

 attending droves of young Membracids in Colorado. The Homoptera 

 responded to the antennal caresses of the ants in precisely the same 

 manner as plant-lice and scale-insects. In Maine and Massachusetts 

 F. glacialis and subsericea are often found attending Piiblilia concava 

 on the stems and petioles of golden rod. I have described and figured 

 (K}o6b) the sheds constructed by our eastern Formica Integra over 

 small colonies of 1'anditzea arcuata about the trunks of young birch 

 trees. 



As the relations between ants and the various Homoptera above 

 mentioned have been regarded as mutualistic, it may be well, before 

 proceeding further, to marshall the facts which seem to warrant this 

 interpretation. The term " mutualism " as applied to these cases, means, 

 of course, that the aphids, coccids and membracids are of service to 

 the ants and in turn profit by the companionship of these more active 

 and aggressive insects. Among the modifications in structure and 

 behavior which may be regarded as indicating on the part of aphids 

 unmistakable evidence of adaptation to living with ants, the following 

 may be cited : 



1. The aphids do not attempt to escape from the ants or to defend 

 themselves with their siphons, but accept the presence of these at- 

 tendants as a matter of course. The same patient attitude is exhibited 

 by coccids and membracids. 



2. The aphids respond to the solicitations of the ants by extruding 

 the droplets of honey-dew gradually and not by throwing them off to a 

 distance with a sudden jerk as they do in the absence of ants. Even 

 at such times, or when artificially stroked with some delicate object in 



