50 



U.S. NATIONAL MUSEUM BULLETIN 259 



Table 4. — Comparison of the mean size ' of sexually mature individuals from different 

 ■populations of Stygonectes pizzinii {Shoemaker) 



1 statistical significance by t-test between different population size means of females: 

 Reftons Cave: Wetzels Spr. (p<.001) Silver Mine: Gables Woods (p<.05) 



Reftons Cave: Chester Co. (p<.001) Wetzels Spr.: Cables Woods (p<.OOI) 



Reftons Cave: Gables Woods (p<.001) Wetzels Spr.: Cliester Co. (.05<p<.10) 

 Reftons Cave: Silver Mine (not sign.) (not sign.?) 



for determining sexual maturity in males appears, however, to be the 

 prominent distoanterior lobe of the seventh pereopodal basis. This 

 structure, however, apparently increases in size with age, and it is, 

 at best, a subjective judgment as to exactly when this structure has 

 reached the stage of being indicative of sexual maturity. With 

 females, as already pointed out, sexual maturity is apparently reached 

 when brood plates become marginally setose, thus providing a well- 

 defined criterion for determination of maturity in this sex. 



