THE WEB OF LIFE 351 



through an island in the middle of a river, are large collec- 

 tive tasks, which are especially interesting because they do 

 not justify themselves greatly, if at all, until they are 

 finished. 



Domestication 



It is very well known that a few species of ants treat 

 certain Aphides or green-flies as if they were domestic 

 animals. They ' milk ' them, stroking them with their 

 antennae, and inducing the exudation of some drops of 

 ' honey-dew. ' They stable them underground in the winter 

 and put them out to pasturage again in the early summer. 

 But this weU-known case does not stand by itself. 



Many years ago Fritz and Hermann MiiUer described 

 how the larvae of a Membracid (Potnia or Umbonia) were 

 used as milk-cattle by a Brazilian stiagless bee {Trigona 

 cagafogo). The bee in question is somewhat remarkable 

 for its tastes ; it is very fond of oily matters and frequents 

 flowers with many glands ; it also feeds on carrion and is 

 attracted to rotten cheese. Its popular name of ' spit-fire ' 

 alludes to its intensely irritant venom, for although it is 

 stingless, it has well-developed poison-glands. 



Approximating to domestication is the extraordinary 

 relationship, described by Viehmeyer, between a species of 

 ant from Manila {Camponotus quadrisectus) and a Lepidop- 

 terous pupa. The ant makes a weU-known hanging earthen 

 nest and the pupae are found in special cells in the centre. 

 When the nest was broken the furious ants grouped them- 

 selves around the pupae as if to protect them, but closer 

 investigation showed that their anxiety was not disinter- 

 ested. At the posterior end of the pupa there is a curious 

 chitinous crater, and opening into this a gland which seems 



