ON THE nEVELOPMENT OF SEX IN SOCIAL INSECTS. 195 



and wings, and with the generative organs in a very imperfect con- 

 dition, so that they are incapable of copulation and are usually in- 

 capable of laying eggs ; they are, however, provided with certain 

 structures not possessed by the cpieen, which enable them to carry on 

 the labour of collecting pollen and doing the necessary work of the 

 hive. 



In termites and ants much the same general principles with regard 

 to the 2^i''>ductiou of males, queens and workers appear to hold good ; 

 but Grrassi has shown tliat, in the case of the latter, the community 

 determine, still using food as the stimulus, whether the insect shall be 

 an ordinary worker or a modified worker, i.e. a soldier. 



The out-and-out Lamarckian attributes this difference in develop- 

 ment to the difference in the character of the environment (the 

 determining factor of which in this case is food). The Darwinian ex- 

 planation is much more complex. Darwin leaves out all consideration of 

 food, and states that occasionally animals in a state of nature are sterile, 

 that if insects were occasionally sterile and sterile forms were found to 

 be useful to the community, natural selection would preserve such. He 

 points out also that the neuter insect differs greatly from its fertile 

 parents. It is also absolutel}^ sterile, so that it could never have trans- 

 mitted specially acquired modifications of structure or instinct to its 

 progeny. The special structural characters of the neuter insect ajDpear, 

 however, always to be correlated with its sterility. The process of 

 natural selection may be applied to the community as well as to the 

 individual ; hence, selection has in this case been applied to the family 

 and not to the individual for the purpose of gaining a serviceable end. 

 Furthei', slight modifications of structure and of instinct correlated 

 with the sterile condition of certain members of the community have 

 proved advantageous, consequently the fertile males and females have 

 flourished and transmitted to their fertile progeny a tendency to produce 

 sterile members Avith the same modifications, and this process has 

 been repeated an immense number of times until the differences between 

 fertile and sterile females have been arrived at. Darwin further states, 

 that the neuters having been formed, variation in the neuters would 

 lead to natural selection bringing about such forms of variation as are 

 of the greatest use to the community, that where two forms of neuters — 

 workers and soldiers —have been developed, these are the extremes of a 

 series of variations, the extremes having been preserved because both 

 are of use to the community, whilst the intermediates have been weeded 

 out by continual selection. 



For myself I am unable to see how food as a factor can Ije left out. 

 Allowing the influence of food as the primary cause of determining the 

 direction which the female larva shall take, one can understand that 

 modification may not be due so much to the direct quantity (or quality) 

 of the food tending to produce actual structures in excess or defect, as 

 to the indirect influence that it exerts (as a stimulus acting on the 

 organism as a whole) in causing the organism to j^roduce certain 

 structures in the case of the queen, others in the case of the worker. 

 It is not simply the quantity of the food-suppl}' which determines 

 the final result, but rather the influence of the food-suppl}'^ on the 

 system, because it apjiears evident that the larvas, whether they finally 

 produce queens or workers, get as much food as they need, once the 

 point is determined as to which form of the female they shall produce ; 



