NO. 2222. NORTH AMERICAN ONYCHIURINAE—FOLSOM. 643 



Left. Right. Left. Right. Left. Right. Left. Right. Left. Right. 



Abd. 1 1 10 10 1 



Abd. 2 1 10 1 10 



Examples I'l 11 7 4 



Abd. 1 1 I 1 I X 



Abd. 2 1 1 X 



Examples 1 1 1 1 



Abd. 1 1X11 10 



Abd. 2 X X 1 1 



Examples 1112 1 



In a few instances pseudocelli were present in a rudimentary 

 condition, as indicated by X in the foregoing tables. 



These tables show that both pseudocelli on the left side were 

 lacking in 30 per cent of the specimens and those of the right side, 

 in 22 per cent. 



On finding these variations I examined some 80 specimens in 

 search of the normal condition (1+1 on both segments), but failed 

 to find a specimen that was not abnormal in material from Cham- 

 paign County, Illinois, from several localities, some of which were 

 12 miles apart. The few specimens that I had from New York State 

 also showed the same kind of variation. Of 15 specimens from Penn- 

 sylvania, however, 14 were abnormal and one was normal, having a 

 pair of pseudocelU on each of the first two abdominal segments. 



Schaffer ('96, p. 162) has recorded the fact that certain variations 

 in the distribution of the pseudocelh appear sometimes to characterize 

 entire colonies. He found that a large number of individuals of 

 OnycMurus armatus from a single locaUty all lacked the pseudocelli 

 of the mesothorax and of the third abdominal segment. In the case 

 of 0. suhtenuis, however, the variation is not hmited to a single 

 locahty, but occurs in 99 per cent of all the specimens from three 

 States, the form regarded as "normal" being in fact extremely 

 rare. The species exhibits primarily a strongly inherited varia- 

 biUty of the pseudocelh of the fii"st and second abdominal segments, 

 and secondly a wide range of individual variation in the distribution 

 of the pseudoceUi on these segments. 



The tooth of the unguis varies in size and is absent in some of the 

 specimens from Pennsylvania. The setae of the body are somewhat 

 longer in specimens from New York than in those from Illinois. 



This species occurs abundantly under logs or dead leaves on damp 

 soil. 



New York: Near Keuka Lake, October 31, C. R. Crosby. 



Pennsylvania: Harrisburg, November 14, H. A. Surface. 



Illinois: Homer, April 2, 3, 9, May 7, 8, June 6, November 7, 25; 

 Urbana, February 19, March 13, 17, April 5, 11, 12, 18, 19, 25, 

 May 3. 



Ootypes.—C&t. No. 20764, U.S.N.M. 



