42 BRITISH ANTS. 



etc. This does not seem to be a very satisfactory definition, as all 

 the workers in a colony, intermediate between the macrergate and 

 the micrergate, would be called desmergates. 



29. The dinergate, or soldier (which is indicated by the symbol 

 for Jupiter " 14. ", to distinguish it from the worker, for which 

 that of Mercury " " is used) is a macrergate with a greatly 

 developed head. The jaws are often very large, long, or massive, 

 and the thorax sometimes approaches that of the female in struc- 

 ture. The name " soldier " is not very happily chosen for these 

 forms, as they by no means only fight and guard the nest, but also 

 perform other special functions, in different species, such as crush- 

 ing seeds, using their heads to act as " front-doors," etc. They do 

 not occur in any British genera. 



Polymorphism is so vast and complicated a subject, and so many 

 different opinions have been offered to explain the origin of its 

 various phenomena, that it can only be further discussed very 

 briefly in this work. Anyone who is anxious to study the subject 

 more deeply, will find the whole matter thoroughly dealt with by 

 Emery, Escherich, and Wheeler. 



The chief problem of polymorphism is to account for the various 

 worker forms, and those such as the soldier, pseudogyne and 

 ergatogyne, etc., which are intermediate between the worker and 

 the female. 



Weismann believes that the various castes are represented in 

 the egg by corresponding units, fertilization being the stimulus which 

 calls the female determinants into activity, and meagre feeding the 

 stimulus which arouses the worker -producing determinants in the 

 young larva from fertilized eggs. 



Herbert Spencer thought that the female castes were not pre- 

 determined, but that they were brought about by differences in 

 the feeding. Neither of these opinions offers an adequate explana- 

 tion ; it is certain, however, that both qualitative and quantitative 

 feeding do exercise considerable influence in the matter. 



A point that requires explanation is the fact that " queen " 

 ants are not reared in captivity, the only exception being recorded 

 by the late Lord Avebury. He mentions that the nest in question 

 had been richly supplied with animal food, which he says may 

 possibly account for the fact. In my own experience, however 

 well fed my ants may have been, I have never succeeded in getting 

 females produced in my observation nests.* 



This would seem to show that either (1) the workers are unable 



* Just before going to press a number of winged females have hatched 

 from pupae in my observation nest of Myrmecina graminicola. I have had 

 this colony in my possession for over five years (see page 81) ; these females 

 must therefore have been produced from eggs laid in captivity ! The ants 

 in this nest have been supplied with a large amount of animal food during 

 the last six months. 



