May 16, 1902.] 



SCIENCE. 



Ill 



They are fed, groomed and guarded by the 

 numeroiis workers of the colony and may 

 therefore be said to live in a condition of 

 domestication like the queens and males. 



During the past three years I have had 

 many opportunities to examine Pheidole 

 colonies in different stages of growth, and 

 my observations bear out the following gen- 

 eral conclusions which agree with those 

 advanced by Adlerz: 



1. Both the morphological and color 

 variations increase both absolutely and 

 relatively in number as well as in ampli- 

 tude with the increase in the number of 

 individuals in the colony. 



2. This increase in variability is also in 

 direct proportion to the increase in the 

 trophic status of the colony. 



The truth of these statements will be ap- 

 parent from a consideration of a few cases. 

 The first offspring of the mother queen of 

 a Pheidole colony consist of a few very 

 diminutive workers only. The second batch 

 of young, at least in one nest of Ph. dentata 

 which I examined, Avere, with a single ex- 

 ception, also workers, though larger than 

 those found in the earliest stage of colony 

 formation. This single exception was a 

 soldier, with a much smaller head than 

 that of the typical soldiers of this species, 

 and its coloration was that of the workers. 

 In more advanced nests the typical soldiers 

 make their appearance, at first a few, then 

 more, till they are abundant in old and 

 well-established colonies. But they never 

 become as numerous as the workers, since 

 the latter are being continually reared in 

 considerable numbers during the whole life 

 of the colony. It is easy to observe, with- 

 out resorting to statistics, that the number 



another pit-fall in the same locality two large ants 

 {Camponotus sansaieanus) were being treated in 

 the same manner by the soldiers and workers of 

 Ph. splendidula. These observations are suggestive 

 in connection with the problem of ' communica- 

 tion ' among ants. 



and range in the color variations in both 

 the soldiers and the workers keep increas- 

 ing, and in polymorphic forms, like Ph. 

 instabilis, the heads of the soldiers show a 

 remarkable progressive enlargement and 

 increased complication in the details of 

 coloration and sculpture. I have repeatedly 

 found incipient nests of this species con- 

 taining only workers and the small-headed 

 soldiers of different sizes, so that I was at 

 first deceived as to the species of Pheidole 

 I had before me. One nest, examined dur- 

 ing the current year, contained only a 

 single soldier of the extreme, large-headed 

 type so characteristic of the species. Such 

 soldiers appear in considerable numbers 

 only in very large, i. e., old nests, and it 

 is only in such nests that one finds, during 

 late May, the highest efflorescence of the 

 colony, the hosts of males and winged 

 females. The soldiers of the extreme type 

 in Ph. iiistaiilis assume a monstrous, one 

 might almost say hypertelic, appearance, 

 the head being so large in proportion to 

 the body that it may lead to serious results 

 to the insect. I observed that when one 

 of these soldiers happened to fall on the 

 back of its head in one of my glass nests, 

 it was often quite unable to right itself, 

 but stood on its head wriggling its tiny 

 body and legs for hours till it could clutch 

 at a passing soldier and thus regain its 

 normal position.* 



It is an interesting fact that the workers 



* This observation suggested some experiments 

 with isolated soldiers. When these are dropped 

 on their heads from a little height on a smooth 

 surface, like clean glass or polished wood, they 

 are often quite unable to regain a footing. 

 Many remain in this position for hours or even 

 for two or three days, struggling at brief inter- 

 vals and finally dying of hunger or fatigue. If 

 a bottle, the inner surface of which is moistened 

 with a drop of chloroform or alcohol, is placed over 

 the insect, it is at first stimulated to the utmost 

 exertion to right itself, but it often dies of suffo- 

 cation without being able to turn over. 



