26 RETROGRESSIVE DEVELOPMENT IN NATURE. [IX. 



habit of sallying forth in troops from time to time, to make 

 raids upon and plunder the nests of some weaker species, 

 such as the common Formica fusca. The object is, however, 

 not to destroy or devour the ants they attack, but merely to 

 carry off the pupae to their own nest, where they receive 

 every care : the workers hatched from them are then employed 

 as servants, or, to use the usual term, as slaves. These slaves, 

 fulfil all the duties of the nest, which would otherwise have 

 fallen to the share of the red workers ; they feed the larvae, 

 build galleries and chambers, bring in food-supplies, and even 

 feed their lazy masters ! This is no fable, as was once thought, 

 but an ascertained fact, proved to be such early in this century 

 by Huber of Geneva, a celebrated observer of ants, and since 

 fully confirmed b}'- his pupil and successor Auguste Forel, 

 as well as by Sir John Lubbock. I have also convinced myself 

 of the truth of the assertion. 



The most curious part of it, however, is that, in consequence 

 of being constantly fed b}'' their slaves, the red ants have 

 entirely forgotten how to procure food for themselves. If they 

 are shut up and supplied with honey, which is their favourite 

 food, they will not touch it, but will suffer hunger, become 

 weak and feeble, and ultimately die of starvation, unless pity 

 is taken upon them and they are given one of their dusky 

 slaves. Directly this is done, the slave falls to work, eats a 

 quantity of the honey, and then proceeds to feed its masters, 

 which are perfectly willing to be saved from starvation in this 

 manner. 



Here, then, as in the case of nestlings, the food-seeking 

 instinct and the power of distinguishing food by sight have 

 degenerated, and clearly in consequence of disuse. Inasmuch 

 as a colony of red ants always owns plent}^ of slaves, the 

 food-seeking instinct has become unnecessary, natural selection 

 has ceased to affect it, and it has gradually died out. Other 

 instincts too have been lost by these red ants in consequence 

 of their habit of keeping slaves; they have quite forgotten 

 the art of nest-building and in part that of tending their 3^oung. 

 Other species of ants devote much attention to their pupae, 

 moving them about the nest from time to time, and often 

 carrying them out into the air and sun, and the}'' feed their 

 larvae with the greatest assiduity. But the red slave-making 



