150 ./ATS. 



mate symbiotic relations would lie ini])ossil)le between species of very 

 diverse habits. 



3. The host, being in all cases a very widely distributed and abun- 

 dant species, forms an omnipresent substratum, so to speak, on which 

 the sporadic parasitic forms manage to graft themselves. That the 

 latter are either rare ants or abundant only in circumscribed localities, 

 suggests that the adoption of their queens by alien workers is beset 

 with manv obstacles. The colonies of some of these ants, like those 

 of /". rnfa and exsectoides, when once established, may, indeed, grow 

 to enormous dimensions and extend themselves over a number of nests 

 by repeatedly adopting fertile queens of their own species, but the geo- 

 graphical distribution of these forms is never as continuous and uniform 

 as that of the host. 



4. The hosts of the temporary parasites are, as a rule, cowardly 

 and prolific species. Both of these peculiarities fit them for being 

 exploited, not only by these parasites, but also by the slave-making ants. 

 And as ant colonies are the more timid and conciliatory the smaller 

 they are, we find that the parasites prefer incipient or moribund colonies 

 to the larger and more aggressive communities of the host species. 



5. Temporary parasitism, being transitory, has not, as a rule, pro- 

 foundly affected the morphological characters of the species. The 

 workers, in fact, have remained unaffected, though the female, in 

 whom the peculiar habit centers, certainly shows structural and instinc- 

 tive peculiarities that can be interpreted only as adaptations to a para- 

 sitic life. Such are the dwarf stature, the mimetic coloration, the long 

 yellow hairs of F. ciliata and crinita, so like the trie-homes of many 

 myrmecophilous beetles, and the conciliatory and insinuating behavior. 



6. The production of a great number of dwarf females by pure 

 adult colonies of F. consocians and A. tennesseensis bears a very inter- 

 esting and suggestive resemblance to the production of a vast number 

 of minute eggs by many nonsocial parasites like the ascarids, cestodes, 

 Saccnlina, etc. This has been universally regarded as an adaptation 

 to the great destruction of individuals incident to the complicated and 

 arduous efforts of the parasite to get a foothold on or in its host. The 

 exception to this rule furnished by the macrogynous Formica: of the 

 ni fa and c.rsccta groups may be due to the fact that in these species 

 the queens are so often adopted by workers of their own opulent colo- 

 nies, and the occasions on which they actually need to found colonies 

 with the aid of alien species so infrequent, that they have not become 

 dwarfed in stature and have not developed pronounced mimetic or 

 myrmecophilous characters. 



