Videnskabelige meddelelser

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Videnskabelige meddelelser

17

sig (1900, p. 422), Thon (1901, p. 125, 1906, p. 40) and M u s-

selius (1914, p. 61). All the authors agree that the mites

lav an extreme number of eggs and that they are laid almost

simultaneously and upon the same rather restricted localities. Espec-

ially E. e.vfendens (O. F. M.) has been studied but it is a very

difficult matter to distinguish the different species from each other;

therefore it is also rather problematic whether the determination

of the species has always been quite correct.

Neuman and Piersig

The egglaying takes place in July ;

indicate that of eggs produced in aquaria some hibernate and do

not develop before next spring. The stage into which the larvæ

arrive in spring is the same in which they appear in autumn. The

great eggmasses are glued as a coherent cover to the substratum

and concealed beyond a protecting layer of yellow hyaline gelatine

through which the scarlet stained eggs are showing.

Thon (1901. p. 124) has made the interesting observation

that the newly laid eggs lack the layer of gelatine; he has ob-

served that the females ran slowly over these eggmasses; the

apex of the snout being pressed against them ;

from

the mouth a

secretion, which immediately hardened in the water, ran out over

the eggmasses, joined the individual eggs to each other and pro-

tected them ;

the secretum is probably derived from the salivary

glands, the volume of which varies at the different seasons. Ac-

cording to Neuman it bardens to a mass so remarkably hard

that it can only with difficulty be pierced by a needle.

The larvæ are hatched in the first days of August (Thon).

Duges (1834, p. 159) has seen them swimming. Krendowsky

maintains according to Musselius (1914, p. 63) that they shall

arise to the surface by means of airbubbles derived from the water-

plants. Arrived at the surface they run upon this as also stated

by Neuman (1880, p. 107) with an extreme velocity searching

for insects which for the egglaying purposes visit the pond. When

the Eylæis eggmasses are to be hatched the leaves of Xiiphar

and Xymphæa are stated to be coloured red by the enorm-

ous masses of larvæ (Musselius). According to Thon (1901,

p. 125) they shall also seek on to mud and vegetation. The hosts

are not with certainty known. Krendowsky maintains that the

larvæ seek on to „die aus der Puppenhiille ausschliipfenden Mucken

Vidensk. Medd. fra Dansk naturh. Foren. Bd. 70. 2

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