526 ANTS. 



association obtain> it> food only from the tongues of the Mynnica 

 workers ( /'. c., by regurgitation), or by licking their oily bodies, but 

 when it is separated from the Mynnica in an artificial nest, it begins 

 to visit the food dish and feeds, rather awkwardly at first, but eventually 

 quite like the nonparasitic species. In this case, an instinct, which 

 would certainly be put down by the casual observer as completely 

 absent, can be resuscitated under experimental conditions. The nidi- 

 fication of ants also furnishes examples of vestigial activities. Cre- 

 inastogastcr lincolata, c. g., a common North American ant, which nests 

 in the ground or in rotten wood, belongs to a largely tropical, arboreal 

 genus, many species of which construct great paper or carton nests, 

 roughly resembling the nests of certain social wasps (see Chapter 

 XIII). On very rare occasions, however, and in moist localities which 

 somewhat resemble the jungles of the tropics, C. lincolata constructs 

 small carton nests or diminutive " sheds " of the same material over 

 the plant-lice and mealy bugs on whose excrement it feeds. This is 

 obviously a feeble reminiscence of formerly well developed carton- 

 building instincts. 



That the instincts of ants may become pathological, or, at any rate, 

 result in the production of diseased individuals, was shown in Chapter 

 XXII, where I described the habits of Lomcchusa and Xcnodusa. The 

 presence of these parasitic beetles in the nest causes the ants to 

 neglect their own brood and even to rear abnormal or defective indi- 

 viduals (pseudogynes), which are of no use to the colony. A similar 

 aberration of instinct is seen in the rearing and toleration of the mer- 

 mithergates in nests of Pheidole couninttata, and perhaps also in the 

 production of workers of the intermediate type in nests of Ph. instabilis 

 infested with Orascnw. 



All of these parasites eventually bring about the decay of the colony 

 in which they establish themselves, through a disturbance of its trophic 

 status, or balance. This balance is an extremely delicate adjustment 

 to the food supply and any change in it is very soon reflected in the 

 growth or decay of the colony as a whole. Such growth or decay is 

 best gauged by the appearance or disappearance of the brood, or of 

 certain castes which require an unusual amount of food for their main- 

 tenance. Favorable trophic conditions show themselves first in the 

 increase and growth of the brood, and unfavorable conditions in 

 the arrest of its growth and its disappearance. The second indication 

 of prosperity in a colony is the increase in the number of large workers 

 or soldiers and the appearance of virgin queens. Pricer and I have 

 shown that incipient colonies of ants contain only minim workers and 

 that the major and maxima forms and the queens appear only after 



