228 BRITISH ANTS. 



which was situated in and at the roots of an old stump. As we took 

 two specimens of a beetle (Myrmedonia humeralis Gr.) in this nest 

 the primary host of which is D. fuliginosa and as some of the 

 inner wood of the stump showed traces of the black colour caused 

 by the latter ant in trees infested by it, I suggested that the stump 

 had originally been inhabited by fuliginosa 5 *. Subsequently when 

 referring to this record I stated " I now believe that this (the 

 black colour of the wood) was caused by the umbratus themselves, 

 as, this year (1912), I have found several nests in the ground under 

 heather at Weybridge, with what were evidently black carton cells 

 for the larvae, deep in the nest at the roots of the heather." 60 In 

 September, 1913, 1 dug up a nest of umbrata at Wellington College, 

 which was situated in the ground at a spot where formerly a tree 

 root or stump had been present, this being nearly entirely decayed. 

 Cells of hard earthy carton were found attached to the roots of 

 plants, which on analysis were found to be composed of : 



1. Numerous hyphae of a fungus, with spores, apparently. 



2. A few fine root-fibres (?) of the plant supporting the cells. 



3. The bark of the root (rhizome) (?) of the plant supporting the 

 cells. 



All these were much more numerous in the dark-coloured cells 

 than in the paler ones. 



4. Quartzite grains. These predominated. 



Some of the root-fibres and bark were, no doubt, taken from the 

 remains of the tree root or stump, and the presence of the fungus 

 would be due to the " cement " used by ants for fastening the 

 quartz grains, etc., together. 



Similar cells, of a darker nature, which were again found at 

 Weybridge, in 1913, also contained fungus 66 . 



On June 12th, 1914, in a bank at Woking I observed some neat 

 carton cells fastened by carton nodules to roots in the centre of an 

 umbrata nest,* and on July 16th I found some more dark carton in 

 an umbrata nest at Weybridge, its blackish colour contrasting 

 strongly with the light coloured sandy soil in which it was situated. 



Farren-White undoubtedly describes the carton made by 

 umbrata, though he evidently did not realize the nature of what 

 he saw. He writes : " Again, F. umbrata, as a rule, is found 

 following the occupation of a miner. Lately, when cutting down 

 what was once a magnificent willow adorning my paddock, but 

 which for the last year or so had been gradually losing its beauty 

 and hastening to decay, I was astonished at discovering in the very 

 heart of the tree a strong colony of F. umbrata. It was here occupied 

 as a carpenter as well as a miner. The work of destruction had been 

 commenced, I believe, by a wood-boring beetle, but had been 



* Again in 1915 I found at Woking on May 30th a similar nest to that 

 described in the text above. On the following day my friend Mr. Morice 

 accompanied me there and kindly photographed it (see Plate XII). 



