New Nests of Ants ly Myrmeco])hilous Goleoptera. 415 



means : — (1) by leaving a nest in company with their 

 hosts when the latter seek a new one, the true guests 

 being perhaps * carried by, or riding on the ants, the otlier 

 species running along with them ; (2) by a nest being 

 captured by another colony which may kill off the original 

 holders, and live in their domicile, or during the so-called 

 slave-making raids, when the marauders not only capture 

 and carry off the brood of the other ant, but also the beetle 

 larvae in the nest ; (3) by attaching themselves to winged 

 female ants they might be carried out during the marriage 

 flight and thus come to inliabit the new nest founded by 

 this female. In other cases when the ants fall to the 

 ground, the guests might enter some neighbouring nest, or 

 be taken in by its ants. There is finally Wallace's sugges- 

 tion in the letter to Darwin referred to above — that the 

 ants'-nest beetles occurring in Madeira might have been 

 introduced as ova attached to winged queen ants occasion- 

 ally blown over to the island. 



In order to test the above hypotheses I propose to con- 

 sider the evidence afforded by some of the ants'-nest 

 beetles which occur in Britain. 



Homoeusa acuminata, Mark. 



Normal host?. — Lasius niger, L., and L. fidiginosus, Ltr. 

 Wollaston took this species in a nest of Formica fusca, L. 

 near Bromley, in 1856 (Zool. 1856, p. 5178), and several 

 specimens again in 1857. 



Chitty and I took a few specimens with the same ant at 

 Doddington, Kent, May 12th, 1901 (E. M. M. 1902, p. 74). 



I took a specimen at Mickleham in a mixed nest of 

 Lasius fiavus and niger under a stone May 27th, 1900. 

 As it is unusual for these ants to live together, they were 

 probably encroaching on each other, and eventually the 

 one might exterminate the other. Should L. fiavus have 

 been the victor, we might thus account for a specimen 

 occurring in a nest of this ant. 



O. E. Janson took a specimen running on a bank at the 



* A. R. Wallace, in a letter to Darwin (Z. c. p. 19) remarks : . . . 

 "it may well be that the ova, or larvae, or imagoes of the beetles 

 are not carried systematically by the ants, but only occasionally, 

 owing to some exceptional circumstances. This might produce a 

 great effect in distribution, yet be so rare as never to come under 

 observation." 



