282 INSECT ARCHITECTURE. 



of their streets, vAuch. look as sombre as the most 

 smoke-dyed walls in the older lanes of the metro- 

 polis. M. Huber could not satisfy himself whether 

 it was caused by the exposure of the wood to the 

 atmosphere, by some emanation from the ants, or 

 by the thin layers of wood being acted upon or de- 

 composed by the formic acid.* But if any or all 

 of these causes operated in blackening the wood, 

 we should be ready to anticipate a similar effect 

 in the case of other species of ants which inhabit 

 trees; yet the black tint is only found in the exca- 

 vations of the jet ant. 



We are acquainted with several colonies of the jet 

 ants, — one of which, in the roots and trunk of an 

 oak on the road from Lewisham to Sydenham, near 

 Brockley in Kent, is so extremely populous, that the 

 numbers of its inhabitants appeared to us beyond 

 any reasonable estimate. None of the other colo- 

 nies of this species which we have seen, appear to 

 contain many hundreds. On cutting into the root 

 of the before-mentioned tree, we found the vertical 

 excavations of much larger dimensions, both in width 

 and depth, than those represented by Huber in the 

 preceding cut (page 281). What surprised us the 

 most, was to see the tree growing vigorously and 

 fresh, though its roots were chiselled in all directions 

 by legions of workers, while every leaf, and every 

 inch of the bark, was also crowded by parties of 

 foragers. On one of the low branches we found a 

 deserted nest of the white throat {Sijlvia cmcreciy 

 Tem3Iinck), in the cavity of which they were piled 

 upon one another as close as the unhappy negroes in 

 the hold of a slave ship; but we could not discover 

 what had attracted them hither. Another dense group, 

 collected on one of the branches, led us to the dis- 

 covery of a very singular oak gall, formed on the 



* The acid of ants. 



