FORMICA. 251 



although they were always quite hidden from view ; but sometimes 

 they proved to be uninhabited." 68 



The reason why the undergrowth was better nourished in the 

 neighbourhood of the nests is probably that the soil was loosened 

 by the underground tunnels of the ants, which would have some- 

 what the effect of deep ploughing, and also because the vegetation 

 would be freed from any caterpillars, etc. 



When a rufa hillock has been overthrown, or disturbed, the 

 workers soon build it up again, but if it is continually interfered 

 with, the ants will move to another situation near by. 



Morley asks : " Why this species periodically deserts its nests 

 in the late autumn and is found to possess a brand new one, with 

 all parts complete, some twenty yards or so distant the next 

 spring ? " 59 but this is certainly not the usual habit of these ants. 

 If they find for some reason that the situation they occupy is un- 

 suitable, they will move, perhaps several times, and then they 

 often take part of the nest itself with them. I have seen the ants 

 of this species at Buddon Wood moving the whole nest to a spot 

 near by, the pupae and entire contents of the nest, and most of the 

 nest materials being carried bodily away, and many of the workers 

 were carrying their fellows. 



On the other hand, a nest in a suitable situation will, if undis- 

 turbed, remain on the same spot for a great many years Con way 

 pointed out in 1834 that the old habitations still remain in the same 

 place from year to year 8 , Forel has known a nest (of F. pratensis) 

 at Vaux for over forty years, Charles Darwin in a letter to Forel 

 mentions that an old man of eighty noticed one very large rufa 

 nest in the same place ever since he was a boy 48 , and I have known 

 another at Wey bridge for over twenty years. 



F. rufa occasionally makes its nests in stumps and posts, carving 

 out chambers in the wood, these stumps being often wholly or 

 partly covered with vegetable refuse. 



Forel mentions a curious nest he found near Munich, which was 

 situated at the foot of two posts two metres eight centimetres high, 

 belonging to a balustrade bordering a thick forest. The ants had 

 heaped up materials to the top of one of these, and the interior of 

 the post was entirely sculptured out 39 . 



I have seen rufa colonies at Bagshot situated in tree stumps on 

 a high bank ; no materials were present over the stumps except a 

 quantity of sawdust which the ants had accumulated in boring 

 out their galleries in the stumps. A single colony may have a 

 number of nests connected with one another by runs, paths, and 

 tracks, thus forming a vast community, or ant-town, over a large 

 area. 



A certain proportion of a colony will emigrate and form a new 

 nest with one or more queens, and a colony thus split is enabled to 

 spread in the immediate vicinity where the conditions are favour- 



