EVOLUTION OF INTERSPECIES INTEGRATION AND ECOSYSTEM 



719 



The various types of organisms com- 

 monly found living in close association 

 with social insects, particularly with the 

 ants and termites, are classified by Was- 

 mann (1920) in five ecological categories 

 on the basis of their relationship to their 



Fig. 256. Trachopeplus setosus, a staphylinid 

 syniphile from the nest of the termite, Nasuti- 

 termes nigriceps, in British Guiana. 



hosts: (1) synechthrans, or persecuted 

 predators; (2) sijnoeketes, or tolerated 

 scavengers (Fig. 255); (3) trophobionts, 

 living in the trophoporic field, usually out- 

 side the nest, but attended for their secre- 



bionts and symphiles return some compen- 

 sation to the social insects and receive con- 

 siderable attention from their hosts, much 

 of wliich is doubtless beneficial to the sym- 

 biote, thus estabhshing a true mutuafistic 

 relation. As might be expected, there are 

 various gradations and pecufiar combina- 

 tions of relationships between these various 

 insects and their hosts, but Wasmann's 

 classification seems to have stood the test 

 of time, and the majority of new species 

 discovered fall readily into one or the 

 other of these categories. In some instances 

 there is reason to believe that the categories 

 represent evolutionary sequences. 



Wheeler (1928b), in an expanded and 

 modified version of Wasmann's classifica- 

 tion, gives several examples of relation- 

 ships that are less readily classified into 

 these categories. For instance, the first in- 

 star larva of a Queensland moth, Cyclotorna 

 monocentra, is an ectoparasite on a species 

 of leaf hopper (Cicadellidae) that is at- 

 tended on a tree and "milked" by the ant, 

 Iridomyrmex sanguineus. The caterpillar is 

 carried to the ant's nest, where it trans- 



Fig. 257. Termitonicus mahout, a staphylinid synoekete that rides on the heads of the 

 workers of the termite, Velocitermes beebei, and takes portions of the food passed from one 

 worker to another. 



tions; (4) symphiles, or true guests within 

 the nest, that return exudates to their hosts 

 who feed and guard them (Fig. 256); (5) 

 parasites, both external and internal. 



The synechthrans, synoeketes, and para- 

 sites may be included under various aspects 

 of exploitation and toleration. The tropho- 



forms into a second stage larva that exudes 

 a liquid upon which the ants feed. This 

 larva sucks the juices from ant grubs. The 

 mature catei-pillar follows the ants back to 

 a tree, where it pupates. Here is certainly 

 a peculiar combination of relationships 

 that could be partially classified under the 



