BLACK TERMITE OP CEYLOX. 403 



fragments of wood, which were glued to the struetui'e by a 

 secretion from the mouth (see later for another similar instance). 

 Under normal conditions this does not occur, and it would 

 therefore appear that the wood was used in this case because 

 the supply of normal material had fallen short. That the 

 termites continued to build under such conditions is surely 

 evidence against the surplus material theory, unless it can be 

 assumed that they are impelled by some instinct to be always 

 engaged in building. 



This external structure is in many respects similar to the 

 chimneys of the nests of the mound-building species. It forms 

 a tubular entrance, or a series of entrances, to the nest, but 

 it is not made use of by the workers and soldiers, which enter 

 the nest by an opening near the base of the mass or in some 

 other part of the tree. In the case of the nest shown on 

 PI. XIII. the insects usually emerge through an opening four 

 feet further down the stem, and during the three years which 

 this nest has been under observation, this opening has not 

 exhibited any trace of an external black structure except 

 during February, 1912. Similarly the soldiers and workers of 

 the mound-building species leave the nest, when in search of 

 food, by means of underground passages, not as would be 

 expected via the main entrance, the chinmey. The chimney 

 of the mound -building species is built with the earth which is 

 excavated by the msects when extending the subterranean 

 nest. This earth is brought up to the top and deliberately 

 glued on the top of the chimney ; in this way the chimney serves 

 to get rid of material which is at the time not required. It 

 might be suggested that the black mass is a means of getting 

 rid of decayed wood which must presumably be removed by 

 the black termites when they wish to enlarge their nest ; the 

 walls of the cavity in which the comb is situated are often 

 smoothed down and usually blackened, and they do not bear 

 loose fragments of decayed wood as they would in their natural 

 state. But an examination of the black pellets shows that 

 the material which the termites have eaten has been derived 

 from external sources, not from the wood of the tree. It is 

 indeed probable that they do eat the decayed wood which 

 must be present in the cavity when thej^ first take possession 



6(8)13 " (52) 



