1911] Mann — Some Northwestern Ants and Their Guests 105 



evidence for considering it myrmecophilous, but the repeated 

 occurrence during a period of over two weeks' time may have 

 some significance. The beetle is apparently new, and I am 

 describing it as Aphodius suspectus sp. nov. 



Toward the middle of March, larvae of Microdon were very 

 numerous in the nests. These pupated in the early part of April, 

 and I collected a number to rear. The first adult emerged April 

 20, and others from then until the middle of May. The species 

 is evidently a variety of Microdon tristis Loew. 



One specimen of Cremastochilus pilosicollis was taken on March 

 26, and two more were found in April. Toward the middle of May 

 they became abundant, twenty-eight being taken from one nest. 

 When the nests were uncovered pilosicollis would be seized by the 

 legs and thoracic angles by numbers of ants. In two instances ants 

 retained their grip even after death in the alcohol bottle. Larvae 

 of pilosicollis w^ere often exposed, but the ants did not attack them. 

 I have examined a series of fifty adults from the nest of ohscuripes 

 and failed to find a single mutilated specimen, so this ant must 

 be much more tolerant of Cremasfochilus than Pogonomyrmex, or 

 even Camponotus, with which mutilated beetles of this genus are 

 often found. This is surprising, for to judge from the ordinary 

 behavior of ohscuripes, tolerance is the last quality to be expected. 



One specimen of a small scavenger beetle, Tachyporus californi- 

 cus, was in one nest, and in another a single Cremastochilus knochii. 

 A spider, kindly determined for me by Mr. Banks as Tmeticus 

 perplexus Keyes, was very often found, generally deep in the nest. 

 It may feed on the very young ant larvae. Large spiders, most 

 commonly Thomisidae, are not uncommon on the outskirts of nests 

 of other ant species. They are very often seen holding dead ants, 

 so their proximity to the nest is easily explained. 



Formica rufa subsp. integra var. near coloradensis Wheeler. 

 A number of specimens were sent to me from Medford, Oregon, by 

 Mr. C. M. Keyes, and with them a number of Coscinoptera cases. 

 No adults emerged from these. 



Formica rufa subsp. near integra Nyl. — Several nests exam- 

 ined on San Juan Island. Myrmecophila formicarum abundant. 



Formica fusca var. argentata Wheeler. — Common in vicinity 

 of Pullman, either in independent nests or as slaves of Polyergus 

 rufescens subsp. breviceps Emery. A mixed nest examined March 



