686 Ants’ Nests and their Inhabitants. [August, 
The fourth class of guests in ant-hills can be regarded only as ; 
visitors. They appear to be accidental inhabitants, just as abun- : 
dant elsewhere, but not at enmity with the ants and tolerated by 
them. 
The fifth class, or true parasites, comprises certain minute Chal- 
cids belonging, like the ants themselves, to the order Hymenop- | 
tera, and a peculiar Stylops, one of the most degraded Coleop- $ 
tera known. The latter is known only through some parasitized 
specimens of ants from South America which are now in the 
British Museum. 
That the Chalcids are parasitic is assumed from the habit of 
the others of the group. So far as I know they have never been 
actually bred. 
The Stylopidæ are, as a rule, parasitic upon wasps, principally 
in this country, species of Polistes and the occurrence of a spe 
cies upon an ant is remarkable, for it would seem that the a 
would be able to discover the parasite and rid their infested friend 
of his troublesome guest. l 
There are a large number of other insects found in ants’ nests, 
-such as Acaridæ and Poduridæ, but too little is known of their 
relation to the ants to allow of their being placed in any of the 
categories that I have mentioned. 
The ant-hill fauna of Europe and North America, so far as the 
latter is known, run tolerably parallel. Similar genera are found, 
but thus far only one or two identical species. There are, how- 
ever, a large number of genera found in Europe of which ber 
- have as yet no representatives, and on the contrary we have 
_ forms of very striking appearance which are unknown to them. 
j 
a i a a Aa a A, 
species it is small, and with larger species it also increases in ne 
In shape and appearance the Pselaphide offer remarkable ra 
blances, and it requires a knowledge that the insects are there, 
and a trained eye, to discover them. Mr. Schwarz informs pa 
that on one occasion when collecting in Florida prairie lands 7 
found Ti apinosoma sessile, a small dusky ant, in enormous po 
s. They were everywhere, and covered all the v 
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