682 CLASS IV. INSECTA. 



all refuse including what has passed through the alimentary 

 canals of others, and hence termed proctodaeal food, but the cast 

 skins and the dead bodies of their companions. When the last 

 trace of nutriment has been absorbed from the repeatedly digested 

 food, the ejecta are either left outside the nest, or carried outside, 

 or used in plastering the walls of the galleries. Another kind 

 of food is the regurgitated contents of the crop called stomo- 

 daeal food, and a third is the secretion of the salivary glands, 

 whilst the soldiers at any rate consume alive the bodies of any 

 fellow Calotermes which may be ill or disabled. They occa- 

 sionally kill but do not eat members of other species such as 

 T. lucifugus. The young are at first nourished by the salivary 

 secretion alone, later they take stomddaeal and proctodaeal food 

 and at length are able to support a diet of triturated wood. 



Since as far as we know termites of all grades resemble one 

 another when first hatched ; and since it is evident that the 

 grade of the insect can be determined by the community, for 

 not only can substitution royalties be produced, but forms far 

 along the road leading to the winged state can be diverted 

 and turned into soldiers, their rudimentary wings being absorbed ; 

 it seems evident that heredity cannot be the determining cause 

 of any individual assuming its final grade. Grassi, whose re- 

 searches have done much to throw light upon the problems of 

 termite life, attributes the various forms we know to diet, and 

 it is probable that he is right. 



Termites flourish best in the tropics and subtropics, but a few, 

 as we have seen, spread into the warmer temperate regions. 

 Their nests are made of chewed wood or earth solidified by the 

 excretions of the insect. The earth which forms their galleries is 

 often carried in the form of branching tunnels even on to the finer 

 twigs of the trees they are devouring ; and as these galleries crumble 

 from time to time the soil returns to the surface, and it has been 

 suggested that in Africa termites take the place of earthworms in 

 renewing the surface soil. An Australian species has the pecu- 

 liarity of placing its flattened upright nest with the long axis 

 pointing east and west. In the nests of T. bellicosiis and T. 

 augustatus the nurseries, where the young are reared, are lined 

 with the mycelium of a fungus. The habit which compels a 

 termite to work in the dark, under cover of some excavated 

 tunnel or hastily constructed gallery, is thought to be connected 



