THE ABILITY OF THE MUD-DAUBER TO RECOGNIZE 

 HER OWN PREY (HYMEN.) 



PHIL RAU 



St. Louis, Missouri 



INTRODUCTION 



During the summer months two species of mud-dauber are 

 often seen at the edges of streams, filling their mandibles with 

 the soft mud, carrying load after load to some sheltered spot 

 and fashioning it into a many-celled nest. As each cell is com- 

 pleted the wasp provisions it with spiders, usually paralyzed by 

 her sting, cements her egg to one, almost always the last one 

 brought in, and then seals the cell. The egg hatches and the 

 larva spends its time in devouring the spiders while the mother 

 wasp goes on adding cell to cell until the nest grows to great 

 proportions, sometimes as many as thirty-six cells. 



Of these two species so commonly seen the steel-blue wasp 

 is Chalybion caeruleum and the yellow-legged one Sceliphron 

 (Pelopoeus) caementarium. Our observations are almost entirely 

 upon the latter species. The experiments are for the purpose 

 of ascertaining the wasp's ability to distinguish her own prey 

 or to recognize another's spiders, and her attitude toward such. 



In 1912 * we were watching a Pelopoeus mother industriously 

 filling her cell with spiders. While she was out foraging we 

 borrowed four fine fresh spiders from another new nest near 

 by and with the forceps carefully inserted them into her cell. 

 Upon her return she was at once aware of the intrusion and 

 set about to carry out the foreign spiders with much indignant 

 buzzing. Nor did she stop at this, but carried out and threw 

 away three of her own hard-earned prey as well, before her 

 indignation had cooled sufficiently to permit her to continue 

 her work. It was quite apparent that she recognized the spiders 

 not of her own capture, but why should she reject them because 

 a sister wasp had caught them, and why should she discard a 



1 Ent. News, vol. XXIV, pp. 392-396. 



240 



