264 HENRY C. MCCOOK. 



Adding Stories.— Oq the east and west sides of the hill several 

 inches from the top, deep fissures had been cut, looking like sun 

 cracks, the lower edges of which were being built up, and the upper 

 bent over. An additional story was thus being added to the cone. 

 Here grass-straws were strewn over the summit, and others which I 

 threw upon the hill were dragged into place and utilized with skill. 

 This story was well nigh completed by Monday morning. The build- 

 ing was carried forward (and such was the case on the large hill and 

 on others observed), by erecting warts or small cones upon the sur- 

 face and around the openings or doors of the galleries, and filling 

 between them. I could trace evidently the outlines of galleries 

 laid out. 



Pellets.— The question arose, especially in view of such opera- 

 tions as the covered gallery at Fig. 1, by what means are the pellets 

 of earth, used in building, caused to adiiere to each other? The fact 

 is beyond question in my mind that the ants proceed with intelligent 

 purpose, directed by experience, to spring the arches of galleries and 

 lay out and conduct other building operations. But I was anxious 

 to know whether the pellets were fixed in their appointed places by 

 "mortar" formed from the natural moisture in the soil or by some 

 secretion from the ant. I feel well assured from the fticts above re- 

 corded and kindred observations, that the moisture of rain is neces- 

 sary for the work of construction. The galleries were being enlarged 

 during the dry weather, and the pellets thrown out in large quantities 

 upon several hills; but there was no effort to erect them into stories 

 and galleries for enlarging the hills. The heavy shower was the signal 

 for such work to begin, and it went on energetically and continuously 

 throughout the succeeding period of our stay, during which the effects 

 of the shower upon the earth were apparent. This would seem to 

 indicate that if there be any secretion from the mouth organs of the 

 insect (which I do not think probable), it is insufficient to procure the 

 adhesion of the pellets. A highly suggestive remark was offered by 

 Prof. Koenig. in connection with a verbal communication made to the 

 Acadeniy of Natural Sciences, Philadelphia, of some of the above facts, 

 viz. : that formic acid which is so abundantly extruded by these ants, 

 forifts with the silica of the soil a natural cement. Can it be, that 

 these pellets which are composed largely of sand, are thus cemented 

 together? xVt least, one who may have the o])portunity to make ob- 

 servations similar to these here recorded, should pay particular atten- 



