142 HVMENOPTERA chap. 



Much has been written about the mode in which the variety 

 of forms of a single species of ant is produced. As to this there 

 exists but little actual observation or experiment, and the 

 subject has been much complicated by the anxiety of the writers 

 to display the facts in a manner that will support some general 

 theory. Dewitz was of opinion that workers and c^ueens of ants 

 were produced from different kinds of eggs. This view finds 

 but little support among recent writers. Hart in recording the 

 results of his observations on the parasol ant (of the genus Atta) 

 — one of the species in which polymorphism is greatest — says ^ 

 that these observations prove that " ants can manufacture at 

 will, male, female, soldier, worker or nurse," but he has not 

 determined the method of production, and he doubts it being 

 " the character of the food." There is, however, a considerable 

 body of evidence suggesting that the quality or quantity of the 

 food, or both combined, are important factors in the treatment 

 by which the differences are produced. The fact that the social 

 Insects in which the phenomena of caste or polymorphism occur, 

 though belonging to very diverse groups, all feed their young, is 

 of itself very suggestive. When we add to this the fact that in 

 ants, where the phenomena of polymorphism reach their highest 

 complexity, the food is elaborated in their own organs by the 

 feeders that administer it, it appears probable that the means 

 of producing the diversity may be found herein. Wasmann has 

 pointed out that the ants'-nest beetle, Lomechusa, takes much 

 food from the ants, and itself destroys their young, and that in 

 nests where Lomechusa is abundant a large percentage of erga- 

 togynous forms of the ants are produced. He attributes this to 

 the fact that the destruction of the larvae of the ant by the 

 beetle brings into play the instinct of the ants, which seek to 

 atone for the destruction by endeavouring to produce an 

 increased number of fertile forms ; many ergatogynous individuals 

 being the result. This may or may not be the case, but it is 

 clear that the ants' instinct cannot operate without some 

 material means, and his observation adds to the probability that 

 this means is the food supply, modified either qualitatively or 

 quantitatively. 



The existence of these polymorphic forms led Herbert 

 Spencer to argue that the form of an animal is not absolutely 



' Nature li. 1894, p. 125. 



