ORTMANN: THE CRAWFISHES OF THE STATE OF PENNSYLVANIA 475 
ber or October they have attained a length of from 40 to 50 mm., and the males 
have assumed the first form. The females also are sexually mature, and copulation 
takes place from September to November.” During the winter no changes occur, and 
in early spring they are in about the same condition asin the previous fall. In April 
the females spawn, and it is remarkable that spawning takes place normally from 
four to six months after copulation. The males generally go through the spring 
moult in May, the females a little later in June. This brings up the size of this 
generation to from 50 to 60 mm. ‘Then the fall moult begins, lasting from August 
to October, in which the specimens attain asize of over60 mm. After the first sum- 
mer only two moults, the one in spring and the other in fall, seem to take place. 
At about this time, (October of the second year), the specimens are seventeen 
months old. They go through a second copulating season, and through the follow- 
ing winter, and again through the spring and summer with the same changes, 
attaining by the two moults their maximum size of over 70 mm. in length. A 
third copulating season follows, their age being now two years and five months. After 
this they live until the next spring, when the old males die in April and May, and 
the old females probably in June. This shows the life of the individual to be about 
three years.” 
This seems to be the usual life-cycle of this species. But there are exceptions, 
which are primarily due to the fact that in the first summer the growth of single 
individuals may be quicker or slower. Whether slow growth, inducing late devel- 
ment, influences the total length of life cannot be ascertained, but it must lead to 
the result that some specimens are not sexually mature at the end of the first sum- 
mer, and that thus the first copulation is postponed a whole year; for copulation 
seems to depend directly on the season, and takes place exclusively in fall, but never 
in spring. Furthermore it may be that in single cases life is prolonged an additional 
year, as for instance in exceptionally large individuals (about 90 mm. long). But 
we may safely assume that three years, or at the outside in exceptional cases four 
years, is the duration of the life of this crawfish, and that an individual that lives 
up to this age without having met with an accident has fulfilled its destiny and dies 
a natural death. 
A few additional remarks should be made with reference to egg-laying, moulting, 
and copulation. The act of laying eggs is hard to observe, and I cannot improve 
upon Andrews’ observations on C. limosus quoted above. ‘The process of moulting, 
7 Possibly beginning at the end of August and extending to January. 
73 Andrews (1904, p. 204) was able to trace C. limosus only to the third summer, when the sole survivor of his 
material reached the size of 90 mm. 
