360 ADELE M. FIELDE. 



male offspring only, a queen, Camponotus pennsylvanicus, living in 

 a similar nest of mine, supplied with the same food, subject to 

 the same daily temperature, and having about the same number 

 of worker-servants, produced numerous offspring, exclusively 

 female. The Camponotus queen had been captured when 

 dealated, presumably after her mating. Although these queens 

 were of different subfamilies among the ants, the similarity in all 

 the conditions of their environment except the incident of mating, 

 points to a probability that the sex of their respective progeny 

 was determined thereby, unimpregnated eggs producing males, 

 and impregnated eggs producing females. 



It is an interesting fact that during the twenty-six months that 

 this Camponotus pennsylvanicus queen remained under my ob- 

 servation no male appeared among the many tens of her offspring ; 

 while eleven of her segregated daughters in the care of Dr. Field 

 produced at least three male, and no female, offspring. 



The observations here recorded establish the view that some 

 virgin workers lay eggs, and that many ant-eggs that have had 

 no contact with spermatozoa produce males. Not until female 

 progeny shall have been observed to issue from eggs protected 

 as were those of my Campon'otus pictus should we consider the 

 Dzierzon theory inapplicable to ants. No ant indisputably 

 virgin, with her eggs perfectly safeguarded from spermatozoa, 

 has yet presented evidence against the extension of this theory 

 to the Formicidae. 



MARINE BIOLOGICAL LABORATORY, 



WOOD'S HOLT,, MASS., September 1905. 



