378 WILLIAM MORTON WHEELER 



a pin with a winged female of subsericea, which he had taken 

 July 31 at Westport Factory, Mass., where he had found a 

 large colony of the wasps nesting in a pebbly wood-road. They 

 were bringing in the subsericea queens in great numbers and, 

 curiously enough, were themselves being captured and destroyed 

 by large robber-flies (Deromyia umbrina). 



The queens of the four Formica enumerated above, differ 

 considerably from one another, those of subsericea being much 

 larger than any of the others and those of nitidiventris differing 

 greatly in color, as they have the head and thorax red instead 

 of black. The queens of the true fusca and neoga gates are much 

 alike in size and in being very smooth and shining, but the 

 latter species is readily distinguished by the red color of the 

 legs and the erect hairs on the lower surface of the head. It 

 is significant that all these queens belong to species noted for 

 their cowardly disposition, and as the normal hosts of the slave- 

 making ants (Polyergus lucidus Mayr and the various subspecies 

 of Formica sanguinea Latr.) and of a long series of temporary 

 social parasites (the various subspecies of F. rufa L., truncicola 

 Nyl., exsectoides Forel, etc.). Although nearly all of these pre- 

 datory and parasitic ants are abundant in the Blue Hills, none 

 of their queens is captured by the Aphilanthops. We must 

 assume, therefore, that this wasp has learned to discriminate 

 between different species of Formica and to avoid the more 

 vigorous and aggressive queens of the sanguinea, rufa and exsecta 

 groups. The queens of the microgyna group, represented in the 

 Blue Hills by F. difficilis Emery, are in all probability avoided 

 on account of their diminutive stature. 



That the wasps capture the Formica queens while they are 

 celebrating their nuptial flight and do not take them from their 

 nests, was clear from observations made July 26, for on that 

 day flights of subsericea and sanguinea subsp. rubicunda Emery 

 were observed in the Blue Hills and the wasps were seen bring- 

 ing in numbers of the queens of the former variety. Still I 

 did not see the wasps in the act of capturing their prey till 

 August 15, when there was a great flight from all the colonies 

 of subsericea in Forest Hills and Jamaica Plain, Boston. While 

 walking along the street I saw an Aphilanthops suddenly swoop 

 down onto a queen that had just settled on the ground. Before 

 I could reach the spot the ant had been stung and the wasp 



