﻿NORTH AMERICAN NOTOSTRACA — LINDER 13 



Populations without males, or with very few, have been known 

 for a long time. A list of such cases in A. cancriformis from Europe is 

 given by Gaschott (1928, p. 276), from whose paper the following 

 examples may be cited: Schulze examined more than 1,000 speci- 

 mens dm-ing 4 successive jesiTS from the vicinity of Dresden, Germany, 

 and found no males; Siebold (1871) found only females among about 

 9,000 specimens from Franken, Germany, collected during the 

 summers of 1857-1869, in the last 6 of which he tried to examine 

 the whole population; less extensive samples without males (100-243 

 specimens) are reported from Munich and Erlangen, Germany, 

 Prague, Czechoslovakia, and Pavia, Italy. Further proof of the 

 existence of parthenogenesis in this species is given by Grasser (1933, 

 pp. 319-320), who succeeded in rearing specimens from eggs laid in 

 aquaria populated by females only. These females were taken from 

 a population where no males were observed. Bisexual populations of 

 the same species are also common (Gaschott, 1928). 



Obviously, there are similar conditions in the American species A. 

 longicaudatus. A. oryzaphagus and A. biggsi (Rosenberg, 1947) are 

 probably parthenogenetic populations, and, on account of significant 

 similarities with A. longicaudatus, ought to be included in this species 

 (p. 64). Bisexual populations seem to be more common in this species 

 than in A. cancriformis, and in them the males sometimes are almost 

 as well represented as the females. In such populations there is a 

 greater range of variation in the total number of body-rings. «- 



I have seen a number of relatively extensive samples of LepiduruS 

 arcticus, L. apus, A. cancriformis, and A. longicaudatus with no males. 

 Even here, the variation in the total number of rings is always small. 

 The following sample, a lot of 1 13 females of L. arcticus from Ooglamie, 

 Alaska (U.S.N.M. No. 7903), is representative (no males were found 

 in the sample) : 



Among these specimens the incomplete rings varied in size from a tiny 

 piece to an almost complete ring. No correspondence with size, or 

 with other characters, was observed in any of the groups. The 

 specimens varied much in size. We find, also, that 99 specimens have 

 27 rings and 14 specimens 26 +i rings. This is the whole variation in 



