580 CLASS IX. 



Sp. Limnochares holosericea, A cants aquaticus L. (excl. citatione FRISCHII et 

 SULZERI), EtESEL Ins. ITI. Tab. 25, DE GEER Mem.vu. PI. 9, figs. 1517, 

 KOCH in HERRICH-SCH^FFER DeutscU. Ins. Heft 150, Tab. 24 ; 2"' or 3'" 

 long, elongate, very soft, during life vermilion-red : this little animal creeps 

 on the bottom of morasses and ditches, and upon water-plants. The young 

 animals have six feet, and attach themselves by their sucker to Germ 

 lacustris (p. 443) DUGES Ann. des Sc. not., sec. Serie, I. p. 161. 



Eylais LATE. Palps with basal joints short, penultimate large, 

 last subulate, armed with spines. Rostrum short. Mandibles ter- 

 minated by a movcable claw. Ocelli four, approximate in the mid- 

 dle of the anterior part of body. Feet long, slender ; two posterior 

 pilose, the rest ciliated. 



Sp. Eylais extendens, Hydrachna extendens, MUELL., ffydr. Tab. 9, fig. 4, 

 KOOH 1. 1. Tab. 21, 22 (according to KOCH Acarus aquaticus L., which 

 however is doubtful, and is in opposition to the citation of ECESEL from 



LINNAEUS). 



Hydrachna MUELL. (in part), LATE., DUGES (and Diplodontus 

 ejusd.). Penultimate joint of palps forming with the last a forceps. 

 Ocelli two, or four bigeminous, lateral, distant. Feet ciliated. 



Sp. Hydrachna cruenta MUELL., Hydryphantes cruentus KOCH, DE GEER 

 M6m. vii. PL 9, figs, u, 12, MUELLER Hydr. PL 9, fig. i, KOCH in 

 HERRICH-SCH^FFER D. Ins. Heft 150, Tab. 16. The young animals of 

 this and other species with six feet and a sucker, as MUELLER had already 

 remarked (pullos ex ovis excludi sex tantum pedibus et prdboscide singulari 

 instructos'), are described as distinct species of Acarida by AUDOUIN, under 

 the generic name Achlysia (Mem. de la Soc. d'ffist. not. de Paris, I. 1823, 

 pp. 98 109). DUGES has illustrated this subject by continuous observa- 

 tions, and has made known the entire life of these water-spiders in its 

 different periods, Ann. des Sc. not. 2e SeYie, I. pp. 165 171. From the 

 eggs, which have been laid in spring in the stems of water-plants perforated 

 for the purpose, little hexapod animals come to view, with a large heart- 

 shaped sucker, which might be taken for a head, but that the eyes are 

 situated behind it, on the anterior margin of the back. After an interval 

 they attach themselves to different water-insects (Nepa, Ranatra, Dytiscus), 

 and, whilst the abdomen is growing and extending itself into an elongated 

 sac, the feet and the sucker remain of the same size. In this form the 

 water-spiders were observed by SWAMMERDAM on Nepa (Bijbel der Natuur. 

 PL in. figs. IV. and V.), and described by him as the eggs of this animal, 

 although he had already expressed his doubts whether they were not rather 

 distinct animals, which had their increase by sucking the blood of the Nepa 

 (biz. 230). In this period the animalcules are named Achlysia by AUDOUIN; 

 DUGES then calls them nymphs ; within the skin the perfect animal is 

 formed, like a fly in the pupa coarctata (see above, p. 273). BURMEISTER 

 also, simultaneously with DUGES, announced from his observations that 

 Achtyiia is a youthful form of Hydrachna. OKEN'S his, 1834, s. 138 14 2 - 



