No. 418.] NESTS OF AMERICAN ANTS. 805 
concerning the friendly relations of the two species. By the 
following morning the Leptothorax and most of the Cremas- 
togasters were either dead or dying, having been suffocated 
by the pungent exhalations of the latter species. Thus the 
little I could observe of the relations of the two species 
resembled those which I have recorded for L. emersoni and 
Myrmica brevinodis — only reversed, the L. canadensis behaving 
like the Myrmica, while the Cremastogaster behaved some- 
what like Z. emersoni. 
3. L. pergandei lives, probably as a guest, in the nests of 
Monomorium minutum var. minimum (see p. 539). 
4. The single colony of the Mexican Z. petiolatus which I 
have seen was living in parabiosis with species of Cryptocerus 
and Cremastogaster (see p. 527). 
5. L. tuberum var. unifasciatus lives with the European 
- Formicoxenus vavouxi, the relations between the species being, 
perhaps, the same as those which obtain between Formica rufa 
and Formicoxenus nitidulus (see p. 538). 
6. L. muscorum, L. acervorum, and L. tuberum live as slaves 
or auxiliaries with the European Tomognathus sublevis (see 
PP. 70, 71). 
7. L. curvispinosus probably performs the same rôle in the 
nests of 7. americanus (see p. 715). 
8. L. tuberum has been found associated with Strongy- 
lognathus testaceus. Here, too, the Leptothorax probably acts . 
as the slave of the dulotic species (see p. 710). 
9. L. emersoni lives with Myrmica brevinodis as described 
in the first part of this paper. The compound nest resembles 
that of Z. canadensis with Cremastogaster and of Formicoxenus 
nitidulus with Formica rufa, but the relations between the two 
Species of ants are like those existing in mixed nests. In 
one sense L. emersoni is the dominant species and the huge 
Myrmicas are its auxiliaries, or slaves; in another sense the 
