OBSERVATIONS ON COPULATION AMONG 

 CBAWFISHES WITH SPECIAL REFER- 

 ENCE TO SEX RECOGNITION 



DR. A. S. PEARSE 

 University of Michigan* 



During the past winter the writer kept about three 

 hundred crawfishes in aquaria for a couple of months and 

 had opportunity to observe their copulating reactions 

 from time to time. As the published statements in regard 

 to sex recognition in the genus Cambarus are somewhat 

 meager, the results of some of these observations may be 

 of interest. The species represented in the aquaria were, 

 Cambarus blandingi acutus Girard, C. diogenes Girard 

 and C. virilis Hagen. Most of the observations here re- 

 corded were made upon the last-named species, but noth- 

 ing was observed in the behavior of the others to make it 

 appear that there was any essential difference in the 

 mating reactions of these forms. 



Andrews 1 was the first to give a careful account of 

 copulation in the genus Cambarus. He discovered that 

 while the male holds the female on her back beneath him 

 a spermatophore is transferred from his abdominal ap- 

 pendages to the cavity within the annulus ventralis of the 

 female, where it remains sealed up until the eggs are laid. 

 Andrews gives an excellent account of the details of the 

 process but refers only indirectly to sex recognition. He 

 remarks (p. 868) : 



become aware of the presence of the female and does not act as he does 



