ORTMANN: THE CRAWFISHES OF THE STATE OF PENNSYLVANIA 175 



ber or October they have attained a Iriigth of from 40 to 50 mm., and the males 

 have assumed tlie 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 as in the previous fall. In Ajiril 

 the females spawn, and it i.s remarkable that spawning takes place normally from 

 four to six months after copulation. The males generally go through the spririf/ 

 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 a size of over 60 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 indivi<lual 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 fii-st sum- 

 mer, and that thus the fii-st 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 ca.'^es life is prolonged an additional 

 year, as for instance in exceptionally large individuals (about UO mm. long). But 

 we may safely assume that three years, or at the outside in exceptional cases four 

 yeai-s, 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 limosns (|UoteMi al)ove. The process of moulting, 



" Possibly be^iiinin^ at the end of AnKii.st and extending to .Innunty. 



"Andrews ( 1901, p. 204) was able to trace ('. liiiwsuii only to the tliird siiniiuer, when the sole snrvitor o( his 

 material reached the size of 90 mm. 



