80 Zoologica: N. Y. Zoological Society [HI; 3 



beetles are often kept out of the colony, the fact that the beetles 

 of two or more colonies occupying different petioles, will, when 

 the latter are split open and placed in the same tube, mingle 

 without the slightest signs of hostility, would seem to show that 

 even strange beetles may occasionally enter an unguarded colony 

 and become members of it in good standing. It has since 

 occurred to me that female beetles, at least, might be permitted 

 to pass the sentinels unchallenged. Unfortunately I failed to 

 dissect and determine the sex of the beetles with which I 

 experimented. 



The laxity of the beetles in guarding the entrances is, indeed, 

 amply proved by the presence in their nests of several species of 

 insects, some of which are harmless or indifferent while others 

 are injurious either to the beetles and their larvae or to the 

 coccids. From analogy to the guests of ants, those of the former 

 category may be called "synoeketes," or indifferently tolerated 

 guests, the latter "synechthrans" (predators) and parasites. To 

 the synoeketes belong a Collembolan, a mite and a small Phorid 

 fly. The Collembolan is most frequently seen, especially in large 

 petioles containing small colonies of beetles and therefore allow- 

 ing ample space for its movements. It is a minute silver gray 

 species, which Prof. Folsom has described and figured as Ento- 

 mobrya ivheeleri (Zoologica III, No. 11), and occurs in droves of 

 individuals of all stages, running hither and thither over the walls 

 of the petiole, like certain species of the same genus (E. myrmeco- 

 phila Reut. and dissimilis Mon.) and Cyphodeirus (C. albinos 

 Nicol), which are often abundant in the nests of ants. Like the 

 ants the Coccidotrophus pay no attention to these diminutive in- 

 sects and are probably not even aware of their existence. The 

 mites (Hypoaspis sp.) and Phorid flies (Aphiochieta scalaris) 

 were more rarely seen. They probably breed in the accumulations 

 of refuse at the ends of the petiolar cavity and may therefore 

 be regarded as scavengers, like the mites and Phorids which 

 occur in many ant-nests. 



Careful examination of the alimentary tract of the Coccido- 

 trophus would probably show that the beetle harbors a number 

 of entoparasites, at least certain bacteria, but I could not find the 

 time to make such an examination when fresh material was avail- 

 able and my alcoholic specimens are worthless for the purpose. 



