164 Chapter IV. 



is no possibility of developing into certain forms, there 

 is, of course, no basis, no material for the exercise of 

 the nursing instincts of the workers. From this it 

 becomes clear, why fixed intermediate forms between 

 females and workers occur with certain species, dif- 

 ferent forms with other species, whilst with others 

 again there are none at all. But, within the limits of 

 this natural disposition for further development, there 

 remains to the ants a wide range for exercising their 

 nursing instincts. 



These intermediate forms between females and 

 worker ants I have grouped into six classes, but here 

 we are concerned with but one or two of them. In 

 some of these "evgatogyne" forms it appears almost 

 at a glance, how they came into existence, namely, 

 whether the larva, reared up to a certain stage to be 

 a worker, was later on cared for so as to become a 

 female, or whether the opposite took place. In the 

 first case the intermediate form makes the impression, 

 that the worker-character had been developed to 

 excess ; in the second case, that the female character 

 had been stunted ; in the former the so-called worker- 

 like (ergatoid) queens are the result, in the latter a 

 kind of female-like workers, which I have named 

 pseudo-females (pseudogynes). The former combine 

 the vaulted thorax of females with the small and 

 abdominal development of queens ; the latter unite 

 the vaulted thorax of females with the small and 

 stunted abdomens of workers. Especially the latter 

 form, the pseudogynes, are apparently best accounted 

 for on the score of education rather than by a peculiar 

 disposition inherent in the egg, from which they are 



