May 16, 1902.] 



SCIENCE. 



773 



Pheidole species, but peculiar microgynes, 

 or dwarf queens, certainly occur in some 

 of the members of this genus. Emery* 

 describes a dwarf dealated queen of Ph. 

 pilifera, which was scarcely 3.5 mm. long. 

 Normal queens of this species measure 

 6-6.5 mm. Emery's microgyne exhibited 

 also an aberrant configuration of the 

 epinotal spines. Eeeently Rev. P. J. 

 Schmitt took two similar dealated micro- 

 gynes in the nest of an undeseribed Phei- 

 dole which occurs in Colorado and New 

 Mexico. He kindly sent me one of these 

 insects, which is smaller than any of the 

 soldiers from the same nest. It measures 

 only 2.5 mm., whereas a typical queen of 

 the same species in my collection is 5 mm. 

 long; and therefore eight times as large 

 (in volume) as the microgyne. In this 

 case the microgyne differs from the normal 

 queen in color, pilosity and sculpture, so 

 that had it been captured apart from the 

 colony, it would certainly be regarded as 

 the mother queen of a minute and very 

 distinct species of Pheidole. 



If it is true that the increasing vari- 

 ability exhibited by the Pheidole colony is 

 the result of an increase in the number 

 of its component individuals, and if this, 

 in turn, may be traced to favorable trophic 

 conditions, we should expect to find but 

 little variation in colonies that are poorly 

 fed and therefore unable to increase 

 rapidly in number. This I find to be the 

 case. In central and western Texas during 

 the past autumn and winter the meteoro- 

 logic and food conditions were extremely 

 unfavorable, not only to ants, but to insects 

 in general. Between September and the 

 latter part of March almost no rain fell, 

 and the protracted drought together with 

 the cold of the winter months was very 

 trying even to the ants that feed on stored 



* ' Beitrilge zur Kenntniss der nordamerikan- 

 isehen Ameisenfauna,' Zool. Jahrb., Abth. f. Syst., 

 1894, p. 290. 



seeds. During this period the number of 

 soldiers in the Pheidole nests was found to 

 be unusually small. In some nests of con- 

 siderable size {Ph. dentata) they were en- 

 tirely absent. One might suppose that the 

 soldiers had died off: on account of the 

 unfavorable conditions, but this is im- 

 probable, because the vitality and hence 

 also the longevity of the soldiers is superior 

 to that of the workers, just as the vitality 

 of the queens is much superior to that of 

 all the neuter forms and the males.* I am 

 therefore of the opinion that the scarcity 

 of soldiers in the Pheidole nests was due 

 to their not having been reared by the 

 workers on account of insufficient food, 

 moisture and warmth. Thus there was a 

 tendency to suppress ■ even the normal 

 dimorphic variation of the neuter phase. 



A peculiar Texan Pheidole {Ph. lamia 

 Wheeler) may also be adduced as evidence 

 of the inhibitory effects of unfavorable 

 conditions on variability. Ph. lamia is a 

 very small, timid species which lives a sub- 

 terranean life under stones and feeds on 

 dead insects, myriopods and crustaceans 

 somewhat after the manner of the diminu- 

 tive 'thief -ants' {Solenopsis molesta Say 

 and S. texana Emery). It has the pale 

 yellow coloration so characteristic of hypo- 

 gseic species. Its very small colonies con- 

 tain barely fifty individuals, and though I 

 have found some eight or nine nests of 

 this rare species in different localities and 



* This is easily proved by observations on arti- 

 ficial nests that have not been supplied with 

 the requisite food and moisture. In a nest of 

 Myrmica brevinodis Emery which on September 

 14, 1901, contained forty virgin queens and five 

 times as many workers, thirty of the queens but 

 only two workers were still living March 14, 

 1902. Myrmica brevinodis lives in cool New 

 England bogs, and it was difficult to maintain 

 the right amount of moisture in the nest at all 

 times during six months of very dry Texas 

 weather. In this connection see also Lubbock's 

 notes on longevity in ants ('Ants, Bees and 

 s,' pp. 41, 42). 



