ORTMANN: THE CRAWFISHES OF THE STATE OF PENNSYLVANIA 419 
from the surface. The holes are driven down by the crawfish to such a depth that 
a good supply of water is at the bottom at all seasons. Where the water appears at 
the surface, or is very near to it, the holes are sometimes hardly a foot deep. Gen- 
erally they are considerably deeper, as much as two and three feet. They certainly 
at times go even deeper than this, but I never tried to dig at places where such con- 
ditions prevailed, that is to say, where from all appearances the level of the ground- 
water was more than three feet from the surface. Such conditions were not infre- 
quently met with in the case of C. carolinus. 
In a general way we may say that the holes of C. bartoni are very simple 
(Pl. XL, Fig.8; Pl. XLI, Fig. 1). Among the true chimney-builders the holes 
of C. diogenes are also rather simple, consisting often of a single shaft with a pocket 
at the bottom (Pl. XLI, Figs. 5 and 6). In C. monongalensis they are decidedly 
more complex (Pl. XLI, Fig. 2), and the highest degree of complexity is reached 
in C. carolinus (Pl. XL, Fig. 9). 
The shape of the burrows of C. diogenes was first described by Girard (1852, p. 
89), who called attention to their variable character. Tarr (1884, p. 127) has given 
sketches of burrows of this species, and also observed their variability. Of C. caro- 
linus, only the fact that it is a chimney-builder was known (Faxon, 1885a, p. 71). 
The burrows of C. monongalensis (as dubius) were described by Williamson (1901, p. 
12), and he emphasizes their complexity as compared with those of C. diogenes. 
c. Construction of the burrows and of the chimneys. 
Although the “chimneys” or mud-piles at the mouths of the burrows have 
often been described and their purpose discussed, (Girard, 1852; Tarr, 1854; Shu- 
feldt, 1896; Harris, 1903), the manner in which the crawfish excavates the burrow 
and piles up the mud in front of it had never been correctly observed. Abbott 
(1885) describes how Mr. J. DeB. Abbott saw the crawfish (C. diogenes) engaged in 
building its chimney, and states that it comes out of its hole “ bearing on the back 
of its right claw a ball of clay mud, which by a dexterous tilt of the claw was 
placed on the rim of the chimney.” ‘This description, as we shall presently see, is 
apparently founded upon correct observation, but the observer witnessed only the 
final act, and drew from it a wrong inference. ‘The old observation of Goodman 
(1833, (1842), p. 293), that C. bartoni brings out of its hole an ‘“‘armful of rubbish 
and throws it over the side of his cell, and down the stream,” should be quoted, 
since, although referring to another species, it is pertinent and applies well to the 
regular chimney-builders as regards the mode of carrying the mud.” 
3° The way of carrying the mud out of the holes seems to be identical in all burrowing species. It has been observed 
in a similar form by Mr. W. S. Sutton in C. pilosus Hay, as described by Harris (1900, p. 272). That the crawfish uses 
