16 A Cannditin Arctic Expedition, 1913-18 



corpus with a large anterior lobe extending below the rami, and bearing a pair 

 of lon^ anterior seta* and a pair of short apical setae. Clothing of curving setae 

 of moderate length, longer on the posterior part of the abdomen. Ano-genital 

 segment with two slender simple sensory .setae on each side. Integument tuber- 

 cnlate. Length: female, 1 mm.; male, 0.5mm. 



In small specimens the antenna 1 are shorter than the head. The number 

 of teeth of the inner dorsal lamella increases with age. Thus a female specimen 

 4 mm. in length had seven teeth, and one 0.9 mm. had seventeen. 



The many specimens that I have seen from the United States and Canada 

 agree with the examples that I have received from Europe. 



Sminthurides aquaticus var. levanderi Reuter. 



apic/ilis var. Lcv<inderi Reuter, 1891. 



(H/unticus var. Icrnndcri Schott, 1894. Krausbauer, 1902. 

 x m//w//r//.s- var. levanderi Borner, 1901a. Axelson, 1904, 

 l<.H)r> : i. Wahlgren. 1'HWa, 1906b. (Axelson) Linnaniemi, 1907, 1909, 1911, 

 1912. 



Light or dark violet in colour; in other respects like the typical form. 



The specimens collected by the Expedition belong to this variety, Icrandcrf, 

 and were all females, about half-grown. 



The genus Sminthurides comprises a few species, that are of special interest 

 in several ways. In this genus, as illustrated by S. aquaticus, the persistence of 

 traces of segmentation in the abdomen, an archaic character (Willem, '00), helps 

 us to understand the morphology of the trunk in the more specialized sminthurids. 

 The antennae of the male, with their peculiar hooks and tubercles, are modified 

 to encircle and to hold those of the female at copulation, as described by Renter 

 ('80) and Levander ('94). 



N. (H/unticus, like the other species of its genus, lives on the surface of the 

 water of ponds and streams, where it skips about in a lively manner, owing to 

 structural adaptations of the furcula, particularly the large paddle-like mucrones. 

 The species frequents the leaves of various aquatic plants, but occurs sometimes 

 on pools where there is no visible vegetation. A few specimens that I examined 

 at one time had desmids in the alimentary tract. This species is not limited to 

 fresh water, but has been taken on pools of salt water also. 



N. (H/Hati'dix is a common species in most parts of Europe, and is common 

 also in many parts of the United States. 



Fourteen specimens, from the surface of ponds. Bernard harbour. Northwest 

 Territories, May 2f>. 1<)H>, July 9, 1915. F. Johansen. 



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