AMERICAN HYMENOPTERA. 



Notes on the architecture and habits of FORMICA PENN- 

 SYIiVANICA, the Pennsylvania Carpenter Ant. 



BY REV. HENRY C. MCCOOK. 



In the summer of 1874, my attention was called to a colony of the 

 Pennsylvania Carpenter x\nt, Formica Penns^i/fvanica, De Geer, which 

 had established a nest in a corner beam of Maryann Forge Mill, Blair 

 Co., Pa. At a subsequent visit, August, 1876, I was enabled to obtain 

 the section of the beam containing the formicary. The beam is of 

 white pine, twelve by ten inches thick. This valuable privilege was 

 due to the rare liberality of two of the heirs of the Bell estate, Mr. 

 J. W. Riddle, the manager, and Mr. John Bell. Workmen were 

 employed by these gentlemen to prop up the adjoining timbers, saw 

 out the desired section, and substitute a block of equal proportions. 

 Previous to this a vertical cutting had been chipped from the beam 

 with the aid of augur and chisel, which exposed the interior of the 

 nest quite fully. After the block had been thus removed, I had it 

 sawed into smaller blocks in order to exhibit the entire internal struc- 

 ture of the formicary, of which it was thus possible to make a tolerably 

 complete study. Indeed, the whole series of blocks forms as perfect an 

 example of ant architecture as could well be obtained. 



The first feature that attracts the eye in the vertical sections is 

 this: on one side, and towards the centre the galleries are smaller 

 and more thickly placed. It may be conjectured that here the origi- 

 nal lodgment was made, and that the first galleries were carried up- 

 ward and downward along this axis. As the necessities of the colony 

 grew, and the supporting partitions and columns were reduced to the 

 slightest dimensions commensurate with their purpose, the space re- 

 qu'ired seems to have been procured by extending the boundaries on 

 either side, until they reached within an inch of the surface. 



Turning the attention to this labyrinth of cells with a view to its 

 systematic structure, one observes the evident arrangement into stories 

 and half stories, as represented at Fig. 1, Plate II. The surfaces of 

 the floors are uneven, but may be traced for considerable distances 

 upon the same general level. 8ome of these stories have been formed 

 by driving tubular galleries, which were continually and gradually 

 enlarged, and finally blended. The appearance of corridors or halls 

 is quUe manifest, running parallel in series of two, three, and more. 

 (PI. II, Fig. 1, a, a.) These are separated by columns and arches, or 



