Videnskabelige meddelelser

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Videnskabelige meddelelser

38

(Hermann) is according to Piersig (1900, p. 208) parasitic upon

„Wasserkaferlarven". More thorough explorations upon this inter-

esting field are most desirable.

Subfam. Hygrobatinæ.

With regard to the development of the two large genera Hygrobates

and Megapus Neuman {^= Atractides C. L. Koch) we

hardly know anything. The larvæ of //. longipalpis (Hermann)

and Megapus spinipes (C. L. Koch) is according to Piersig (1900,

p. 190 and 196) parasitic upon larvæ of aquatic insects or upon

aquatic insects.

Subfam. Atacinæ.

The subfam. Atacinæ is the only subfam. of the Hygrobatidæ

of the development of which we have a rather thorough knowledge.

Still this holds good for only a rather few species.

Peculiarly enough O. F. Muller, who has examined the mus-

sels of Furesø and has described Atax crassipes, has not known

that the Atax species are parasites in Unio and Anodonla. It

is Bonz (1783) who was the first to find Acarus ypsilophorus

in these mussels. In the following years they were occasionally

found by Rathke (1797, p. 171). Pfeiffer (1825, p. 28) and v.

Baer (1827, p. 523). Each of these authors gives them a new

name. Say (1821, p. 9) mentions them in North American mussels;

also Dana, further Whelpley (1836, p. 354) and Haldeman

(1842) mention them. In 1850 appears the famous paper of

v. Beneden on Atax ypsilophora (^ A. intermedins Koen.).

Through this paper we get for the first time information relating

to the main points in the development of the Hydrachnids. A

more thorough knowledge we first get through Claparéde's ex-

cellent paper (1868, p. 445). Claparéde has studied three Atax-

species: Atax Bonzi Clap., Atax ypsiloplioras (Bonz) and A. cras-

sipes (O. F. M.). The first named is according to Claparéde only

found in Unio, A. ypsilophorus only in Anodonta; A. crassipes

as parasite is hitherto only known in the transitional stages be-

tween first and second larval stage. Claparéde supposes that

the species being frequent in the rivers (p. 471) is only parasitic

in these stages. Especially Atax Bonzi has been studied. For the

first time (p. 452) we find the five stages in the development of

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