THE TEMPORARY SOCIAL PARASITES. 451 



7. The elimination of the host queen in colonies invaded by the 

 temporary parasites destroys the reproductive powers of the host 

 colony. Hence this form of parasitism is strictly comparable to the 

 castration induced in their hosts by many nonsocial parasites like 

 Sacculina and Stylops. We may therefore designate cases like that of 

 Bothriomyrme.i" and Tapinoina as examples of social castration. This 

 term, as will be shown in the sequel, will apply also to most of the 

 mixed colonies formed by dulosis and permanent social parasitism. 



8. The future development of the temporary parasites may be sup- 

 posed to lead most naturally in the direction of permanent parasitism. 

 This, however, can eventuate only if the species limits and accelerates 

 the growth of its colonies or foists itself only on well-developed colonies 

 of the host. Contrariwise the parasite would outgrow the host colony, 

 or the latter would die off prematurely unless its queen were retained 

 in the nest. We shall see that such Malthusian practices are actually 

 carried out by the permanent social parasites and have resulted in the 

 complete extinction of the unnecessary worker caste. 



