20 Bulletin American Museum of Natural History. [Vo\. XXIII, 



individual, dissected by Professor Montgomery, contained two somewhat 

 smaller parasites, together with many of their eggs. I have seen speci- 

 mens containing as many as six and eight parasites. The specimens 

 dissected by Professor Montgomery were "either fully mature or in M^hat 

 von Linstow^, calls the second larval stage, which is, however, really the 

 immature stage." 



While it is certainly somewhat singular that a species of Mrrmis should 

 occur in ants, even greater interest attaches to the cases under discussion, on 

 account of the manifest effects of the parasite on its host. The fact that all 

 the mermithergates are of huge size as compared with the normal workers 

 is remarkable, for, on first thought, one would certainly expect an animal 

 infested with such large parasites to be stunted, or, at any rate, below the 

 average stature of the species. This paradoxical condition of the mermither- 

 gates of Ph. dentata is easily understood, however, when we make due 

 allowance for certain peculiarities in the behavior of ants. In the first place, 

 it is obvious that the parasite must enter the body of the ant while she is 

 still a larva. This was proved by the fact that two of the large mermither- 

 gates were callows, one of them still very soft and pale yellow, the other 

 with harder integument but without the deep coloration of the mature 

 workers. Such huge parasites could scarcely have made their appearance 

 in ants so recently escaped from their pupal envelopes. But even if there 

 had been no callows among the mermithergates, the truth of the above state- 

 ment would still be patent, both because the mermithergates were all 

 infested while none of the normal workers were found to contain parasites, 

 and because the structure of an ant is, of course, fixed in the pupal stage and 

 cannot be subsequently increased to the dimensions of the insects under 

 consideration. 



It is evident, furthermore, that the larger stature, which is very apparent 

 not only in the distended gaster of the mermithergates, but also in all the 

 other parts of the body, can have its origin only in an unusually large amount 

 of food consumed during the growth period of larval life. Now Ph. com- 

 mutata is exclusively carnivorous and feeds at least its older larvae 

 with pieces of insect food. The workers cannot, therefore, accurately 

 regulate the amount of food consumed by each larva, and it must be possible 

 for larvfe infested with parasites, and hence presumably endowed with a 

 more voracious appetite, to consume a greater quantity and hence produce 

 larger pupae and imagines than unparasltized individuals. If this inference 

 is correct we must suppose that the stimulus to the increased feeding, i. e. 

 the appetite, which results in the larger stature of the mermithergate, resides 



1 Das Genus Mennis. Arch. f. niikr. Aiuit., LIII, 1898, pp. 149-168, Taf. viii. 



