396 Stainforth: The Guests of Yorkshire Ants: 
Staphylinus stercorarius under a stone in an ants’ nest, says 
with a certain amount of contempt, “Oh, that common 
fellow is only an accidental guest ; he’s of no interest to me. 
The genus Staphylinus is not even referred to as a myrme- 
cophile in Wasmann’s ‘ Critical List of Myrmecophilous and 
Termitophilous Arthropods,’ of 1894; therefore I'll let him 
go.”’ Yet it would be a pity if we did not carefully note down 
our observations on the occurrence of species of Staphylinus in 
ants’ nests. Through my finds in the Grand Duchy of Luxem- 
bourg I have come to the conviction that in the case of Staphy- 
linus stercorarius especially, and perhaps also for other species 
in the same genus, we are confronted with a local adaptation 
towards a robber life in ants’ nests, and a commencement 
of “synechthry.”’’ The writer then goes on to give a critical 
account of his observations on Staphylinus species in the field, 
and of experiments carried out in observation nests of various 
ants. He clearly proves that these beetles are able to “ make 
a living’ in ants’ nests at the expense of the inhabitants. 
Terrestrial isopods occur frequently in ants’ nests which 
they doubtless find to be suitable harbourage, their hard 
integument rendering them immune from the attentions of 
the ants. Their occurrence (with the exception of Platyarthrus) 
is, however, doubtless accidental. In the same situation I 
have also frequently found the Pill Millepede, Glomeris margin- 
ata. This was especially the case at Weedley. 
The symbiotic relationship existing between ants and other 
arthropod animals is a subtle and far-reaching ecological 
problem worthy and needy of more attention than has usually 
been accorded to it in our county. If in this paper the beetles 
and spiders have been mainly dealt with it is because these 
particular orders have been more fully studied than others 
equally important and interesting. It is only bya careful search 
in ants’ nests that many of the rarer of our coleoptera and arach- 
nida can be obtained. It is a subject also which appeals to 
some extent to the lepidopterist, for among the myrmecophilous 
symbionts are the caterpillars of some of the Lycaenids which 
are sought after by ants, who lick them and protect them for 
the sake of the sweet secretions they supply. The butterfly 
collector in search of a rare ‘ blue’ finds out first whether 
the ants are there; if they are, the butterfly may be.* It is 
quite possible that the scarcity or disappearance of * blues’ in 
Yorkshire localities has depended upon the scarcity of ants. 
It is often difficult to decide whether an animal is truly 
myrmecophile or whether its occurrence in proximity to a 
colony of ants is accidental. Most cases can be settled by 
umerous independent observations and this is work that can 
arse “limi, Intceee leo)? wos), qo, 217). 
Naturalist, 
