PROCEEDINGS 



OF THE 



AMERICAN PHILOSOPHICAL SOCIETY 



HELD AT PHILADELPHIA 

 FOR PROMOTING USEFUL KNOWLEDGE 



THE PARASITIC ACULEATA, A STUDY IN EVOLUTION.^ 



By WILLIAM MORTON WHEELER. 

 (Read April 25, igig.) 



There is undoubtedly much to be said in favor of the opinion 

 commonly held by entomologists that the fruitfulness of their inves- 

 tigations is apt to be directly proportional to the intensity of their 

 specialization, but it is also true that this very specialization may 

 often preclude an adequate appreciation or even a recognition of 

 phenomena that would profoundly impress the worker who pos- 

 sesses more general biological interests. This statement is not 

 inapplicable to the subject of the following study, which is an at- 

 tempt to collate the data accumulated in their respective fields by a 

 number of observers of ants, bees and wasps and relating to certain 

 types of parasitism w^iich keep recurring in various natural families 

 of the Aculeata in response to frequently recurring stimuli or situa- 

 tions in the organic environment. The few who have published 

 comprehensive accounts of the phenomena have failed to present 

 then! as clearly and cogently as the facts would seem to warrant. 

 I am aware that my own treatment of the subject may leave much 

 to be desired and especially that my account of the bees, a difficult 

 and extensive group to which I have been able to devote compara- 

 tively little study, is rather summary, but every attempt to attain 



1 Contributions from the Entomological Laboratory of the Bussey Insti- 

 tution, Harvard University. No. 155. 



PROC. AMER. PHIL. SOC, VOL. LVIII. A, JUNE II IQIQ. 



