GEOLOGIC WORK OF ANTS—-BRANNER. 333 
We only know that the openings beneath the surface are rudely equal 
to the amount of soil in the above-ground structures. 
RESUME. 
Ants and termites are vastly more numerous in tropical America 
than they are in the temperate regions. 
They show a marked preference for, or rather their structures stand 
up better on, clayey than on sandy soil. 
They affect the geology, especially the soil and subsoil, both directly 
‘and indirectly. 
Directly: 
1, By their habits of making underground excavations that 
radiate from a central nucleus and often aggregate several 
miles in length. 
2. By opening the soil to atmospheric air and gases. 
3. By bringing to the surface large quantities of soil and subsoil. 
4. By introducing into their subterranean excavations large 
quantities of organic matter which must yield acids that 
affect the soil and the subjacent rocks. 
5. By using these excavations for habitations and the produc- 
tion of gases that attack the soil and its contained min- 
erals. 
Indirectly: 
6. By the periodic passage and circulation of meteoric waters 
through their extensive tunnels. 
7. By affecting the availability of the soil for agricultural pur- 
poses. 
8. By affecting the habitability of the land by man. 
9. By the destruction of crops. 
10. By the consumption (by termites) of dead plants and of tim- 
bers and lumber used in houses and for the manufacture of 
furniture, machinery, etc. 
Although the data available are defective, we seem to be warranted 
-in concluding that ants and termites are quite as important geologic 
agents in tropical America as are the earthworms of temperate zones. 
They are also factors of great importance from an agricultural, 
economic, and social point of view. 
