ACARINA 



451 



Fig. 708 Hygro- 



bates longipalpis 



(Wolcott). 



2. FIONA* Koch (Curvipes Koenike). Fourth joint of pedipalp usu- 

 ally with 2 papillae; legs all with swimming hairs; genital pore close 

 behind the hind coxal plates: 19 American species, among the largest 

 and most active hydrachnids. 



P. spinulosa (Wolcott) (Fig. 709). Body broadly 

 elliptical and about .5 mm. long, being one of the 

 smallest of the genus and nearly transparent, with 

 patches of dark brown and a spot between the large 

 eyes; coxal plates close together and covering most of 

 the ventral surface; legs long and with few spines; 20 

 to 30 suckers on each side of genital pore: widely 

 distributed and common in central states. 



3. UNIONICOLAJ Haldeman (Atax Fabricius). Body 



ovoid or round ; genital opening at the hinder end of body, the plate on 

 each side of the opening bearing many minute suckers; pedipalps long, 

 in the parasitic forms thick ; first pair of legs usually thick, in the non- 

 parasitic species with long, movable spines ; third and fourth pair of legs 

 with swimming hairs: 16 American species, most of 

 which are parasitic either in youth or permanently, 

 on the gills of Unionidae and occasionally other 

 mollusks. 



U. ypsilophora (Bonz). Body ovoid, about 1.3 

 mm. long, yellowish-white in color with large brown 

 or black spots, and a yellow Y-shaped mark on the 

 back; about 20 minute suckers on each side of gen- 

 ital pore; first pair of legs not thicker than the 

 others: widely distributed and common in the 

 eastern and central states, occurring, with rare exceptions, in species of 

 Anodonta; Europe. 



U. fossulata (Koenike). Body ovoid, about 1.4 mm. long; 5 suckers 

 on each side of genital pore; first pair of legs not so thick as the pedi- 

 palps : central states, common, occurring, with rare exceptions, in species 

 of Unio. 



4. LiMNESiAj Koch. Body ovoid; fourth pair of legs without the 

 terminal claws, but with a bristle at the tip; pedipalps long with the 

 second joints thickened ; 3 or 4 suckers on each side of the genital pore ; 

 4 eyes: 6 American species. 



* See "The North American Species of Curvipes," by R. H. Wolcott, Trans. Am. 

 Mic. Soc., Vol. 23, p. 201, 1902. 



t See "On the North American Species of the Genus Atax Fabr.," by R. H. Wol- 

 cott, Trans. Am. Mic. Soc., Vol. 20, p. 193, 1899. 



t See "On the North American Species of Limnesia," by R. H. Wolcott, Trans. 

 Am. Mic. Soc., Vol. 24, p. 85, 1903. 



Fig. 709 



Fiona spinulosa 



(Wolcott). 



