VARIABILITY IN THE NUMBER OF TEETH ON THE 



CLAWS OF ADULT SPIDERS, SHOWING THEIR 



UNRELIABILITY FOR SYSTEMATIC 



DESCRIPTION. 1 



CARL HARTMANN. 



Since the number of teeth on the claws of spiders is often used 

 as a specific character, the need of testing its constancy sug- 

 gested itself. It has been pointed out by W. Wagner 2 that the 

 number of ungual teeth varies with each moult. In the present 

 study of the variations in the adult this fact was well taken into 

 consideration, great care being exercised in choosing fully mature 

 individuals that had undergone the last moult. To my knowl- 

 edge no one has ever tested the constancy of the number in 

 fully mature individuals. 



The study was made on the claws of the right legs of 70 

 females and 40 males and comprises, therefore, observations on 

 nearly 1,320 claws of 440 legs. Representatives of a number 

 of different families were chosen as follows : Dictynidae {Dictyna 

 volupis, Keys., West Chester, Pa.), Theridiidae (Theridium tepi- 

 dariorum, Koch, Philadelphia), Pholcidae (Spermaphora sp .? 

 Hentz, Austin, Texas), Epeiridae (Epeira marmorea Clerck ; 

 E. benjaiiiini, Walck.; Acrosoma reduvianum, (Walck), West 

 Chester, Pa.), Lycosidae (Lycosa nidicola, Emerton, Austin, 

 Tex.). 



The counting of the claws was easy except in the case of 

 Dictyna volupis and of Spennophora ; but even here, if any mis- 

 takes in the counting are recorded, they are extremely few, for I 

 never left a claw until convinced that my count was correct ; or 

 in a few cases where this seemed impossible the individual was 

 entirely discarded. To count the teeth the three claws of each 

 leg, if they were large, were snipped off with a needle (keeping 

 the foot on a slide in a drop of alcohol) and pressed flat with a 

 cover-glass. If the claws were too small, the whole tarsus was 



1 Contributions from the Zoology Department of the University of Texas, No. 55. 



2 W. Wagner, " La Mue des Aragnees," Ann. Sc. Nat., 1888, p. 363. 



191 



