152 BRITISH ANTS. 



On September 14th, 1912, I found in a nest of Formica rufa at 

 Weybridge three very large workers of Leptothorax acervorum, 

 which were light in colour, but each possessed a large gaster and a 

 somewhat larger thorax than that of the ordinary worker. 



The female of this species is able to found a colony alone ; the 

 small colony in the oak-apple before mentioned was probably an 

 instance of this kind, and I observed a solitary deflated female in a 

 small cavity under a stone at Nethy Bridge on May 19th, 1912 64 . 



A female may also enter the nest of some other species of ant, as 

 Leptothorax acervorum is often found in such situations. 



This ant is of a peaceable and gentle disposition, it does not 

 attack other ants of its own, or different species, and it does not 

 appear to be attacked by them. On March 7th, 1910, I collected 

 two small colonies of this species at Weybridge, which were both 

 situated under the bark of fir stumps as these two stumps were 

 at a considerable distance from each other, the two colonies could 

 not have been connected in any way and each consisted of a 

 similar number of workers, a dealated female, and some larvae. 

 When introduced into a small, single-chamber, .plaster nest the two 

 colonies were quite friendly together, and joined forces at once, all 

 the larvae were collected into a heap in one corner of the nest, and 

 both the females rested on them 58 . They were kept under observa- 

 tion for nine months, during which time they prospered, eggs were 

 laid, and larvae reared. I have written in my notebook on 

 October 30th " Introduced a dead house-fly into the nest, much 

 excitement noticed, the workers appear to signal to each other by 

 striking the bottom and side of the plaster nest with their gasters." 



A number of instances are on record illustrating how frequently 

 L. acervorum occurs in the nests of other ants of different species : 



Farren-White found a colony at Shirley inhabiting a gorse 

 stump in the centre of a nest of Formica sanguinea 28 ; Rothney 

 records specimens in a nest of the same ant in the same locality 

 previous to 1882 20 , and in October, 1891, being again at Shirley in 

 quest of nests of F. sanguinea, he was indebted, in his success in 

 finding a small colony of that species, entirely to a worker of 

 L. acervorum which by careful watching led him some yards straight 

 to the former's secluded retreat, in which he also found other 

 workers of the latter 24 . Again in 1892 the same observer found 

 specimens of the Leptothorax in and about the nest of sanguinea 

 at Shirley, more especially in April and May. He writes " One 

 worker which I watched entered the nest, remained a few seconds, 

 and came out again in no way interfered with by sanguinea ; but 

 a small nest of Myrmica scabrinodis } situated within a foot or two of 

 sanguinea's, which I opened up, was smartly attacked, and the 

 workers dispersed. These observations seem to point to some fixed 

 relations between sanguinea and acervorum"' 2 ' 1 



Burns took the acervorum in a nest of F. fusca at Bidston Hill, 



