AMERICAN IIYMEXOPTERA. 265 



tion to the use made by the buiUlers while laying the pellets, of their 

 abdiiuiens from which the acid is secreted. 



The thou^iht occurred to mc that the confoi'mation of the pellets 

 themselves might greatly aid their mutual adhesiveness. A number 

 were therefore submitted to close examination. The figures at Fig. 4 

 are magnified drawings of a few of these forms. They evidently are 

 each accumulations of small particles of soil, united in various irregu- 

 lar shapes, by the pressure of the mandibles. Some of them present 

 the appearance of being cut down from larger masses, or cut away 

 upon the face. This may simply be the natural result of nianipulatioQ 

 under that toothed organ which serves the ant as trowel, chisel, spade, 

 hammer and hand. Whether or no these pellets be wrought into their 

 peculiar shapes with deliberate and intelligent purpose ; or, are only 

 an accident of their preparation or handling, it is obvious that their 

 form must greatly facilitate the work of the ant in fastening them 

 together. The irregular faces of the pellets fit into and fasten upon 

 each other, uniting the whole in a way which may not indeed be pro- 

 perly characterized by the terms " dovetailinsr," and "ball and socket" 

 jointing, but which nevertheless gives one a rude impression of such 

 niechanhcal contrivance. 



After having expressed the above opinion in the Academy, I sub- 

 mitted some of the pellets to Dr. Joseph Leidy for 

 observation under the microscope. He gave uie the 

 following opinion : " The pellets, examined by the 

 microscope appear to be composed of several small 

 rounded or ovoidel balls cemented together by the 

 same material. I could detect no special mechan- 

 FiG. 4. — Group of ism like facets or 'ball and socket' jointing." This 

 pellets of soil used y^^^ accompanied by a figure of a representative 

 pellet which is marked L in the group. It will be 

 seen at a glance that it does furnish a rude socket into which the 

 projections upon other pellets might readily fit. 



Ajje or Hills.— What is the age cf these hills? or more properly 

 speaking. How long does it take a community to erect hills of such 

 sizes as are here represented? There are various conditions which 

 must cause a necessary variation in the progress of the work at differ- 

 ent times and places. The condition of the season as to moisture, the 

 oa.ure of the soil, the inroads of enemies, the size and necessities 

 of the community, and other contingencies must make a difference 



