WHEELER— ANT LARV^. 337 



ecto- and entoparasites which are intimately associated with their 

 hosts (e. g., Sacculina, many Copepods, Isopods, tapeworms, etc.). 

 The origin of these strange characters is evidently spontaneous, or 

 mutational and dependent on the favorable conditions under which 

 they arise. In the case of the domestic animals we know that the 

 unusual characters are being continuously and rapidly perfected and 

 established by man's selective activity. It does not follow, however, 

 that the analogous developments of symphiles are the outcome of a 

 similar activity on the part of the ants and termites. The resem- 

 blance of the aberrant characters of symphiles to " hypertelic " 

 structures in many other insects has been noticed by Dahl. That 

 the phenomena in both cases are due to the same cause, i. e., the re- 

 laxation or suppression of natural selection, is much more probable 

 than Wasmann's contention that the ants take the same interest in 

 breeding Paussids and Clavigerids- with extraordinary antennje that 

 we do in breeding lop-eared rabbits and fan-tail pigeons. Nor is 

 there any evidence that even the biologically useful characters of the 

 symphiles, namely their trichome glands and exudate tissues, are 

 engendered or perfected by 'amical selection. The truly amazing 

 cases of convergent or parallel development of these structures in 

 symphiles belonging to the most diverse genera is, in all probability, 

 attributable to the adaptive activities of the symphiles themselves, 

 just as we attribute the convergent development of hooks, suckers, 

 hermaphroditism, blindness, etc., in entoparasitic worms or aptery 

 in ectoparasitic insects, such as lice, fleas, Polyctenids, Nycteribids, 

 etc., to the parasites themselves and not to specifically selective 

 efforts on the part of the host organisms. 



Holmgren accepts Wasmann's ariiical selection and carries it a 

 step further in his contention that it accounts for the development 

 of the various castes in the termite colony. He says (1909, p. 200) : 



If now the above described connection between feeding and exudate 

 secretion holds good, so that the quantity of exudate secretion determines 

 the kind of feeding, it would seem to be self-evident that the exudate secre- 

 tion is intimately connected witli the development of castes, for Grassi and 

 Sandias have shown that feeding is probably to be regarded as a factor in 

 caste development. And if, therefore, the exudate secretion is the cause of 

 feeding we must regard it as the cause of the differentiation of the various 

 castes. 



