Videnskabelige meddelelser

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Videnskabelige meddelelser

22

ates (1897, p. 318) „that the eggs are laid in batches loose in the

water, not being anchored anywhere. They had so nearly the

same specific gravity as the water that the movement in the water,

due to the adults, was sufficient to cause the eggs to rise now

and again nearly to the top of the tube". I am inclined to think

that here we only have to do with an aquarium phenomenon.

Piers i g (1900, p. 392) indicates that the sixlegged larvæ espec-

ially are parasites upon Ciilc.v „die sie bei deren Ausschliipfen

aus der schwimmenden Puppenhiille befållt." When the gnats re-

turn for egglaying the larvæ leave them ; the nymphs are origin-

ally very small ; the second pupa stage takes place upon water-

plants.

Soar (1906, p. 364) maintains that he has found Hydnjphantes

attached to a fly Caenia obscura Mg. belonging to the family

Kphijdr'mæ the larvæ of which live in waterplants. Thon reports

that he has found a nymph of H. dispar (v. Schaub) in the mantle

behind the head of Paliidina contccia, one of the very few state-

ments of Hydrachnids upon snails. Remarkably enough Soar (1906,

p. 364) mentions that also Wesché has found Hijdryphantes

on Paludinci. According to Thon the peculiar coneshaped form

of the rostrum and the sharp claws of the mandible show peculiar

adaptations by means of which the mite is anchored. From this

he expects a similar mode of living for Diplodonlus, Enpalra and

Thyas, which owing to the lack of swimming hairs are referred

to parasitic life. He emphasizes that Thyas is found creeping upon

Paliidina and Planorbis. At this moment it is quite impossible to

reconcile the indications of Piersig and Soar with those of

Thon.

Diplodontus.

D. despiciens (O. F. M.). Duges (1834, p. 155) states that the

newly hatched larvæ swim very well and rise to the surface upon

which they run with extreme rapidity. He supposes that these

larvæ search for Odonata, Tipiilidæ and Cnlicidæ and sooner or

later return to the water again. No direct observations support his

supposition ; the thought has struck him because he has found in

the water both a very small eightlegged nymph probably belonging

to Diplodontus and also others much larger sitting between water-

plants; these nymphs were hatched and Diplodonlus came out.

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