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cules into the holes with the streams running down the trunks and passing through 

 the huge carpets of tree-mosses. Often the surfaces are covered with thick layers of 

 large Podura which later on form a decomposing mass on the bottom. Some gras- 

 hoppers f. i. Meconema varium, Carabidce, Oniscidw, which here, curiously enough, 

 meet with a few living Asellus aquatius but especially many snails f. i. Limax o. a., 

 are swept down into the holes and drowned. 



In dry summers f. i. 1918 the holes contain no water from the first days of 

 August to October; in the course of the autumn the holes were filled, but in De- 

 cember they froze and were frozen till the last days of March. To aquatic animals 

 in the free-swimming stage the holes are only habitable for about four months, but 

 in these four mouths long periods of drought may intervene, and the holes may be 

 laid dry for weeks and even months. 



Curiously enough, these rather unpleasant localities contain a crowd of ani- 

 malcules which have here found a home and are adjusted to the remarkable con- 

 ditions these holes can offer their habitants. Now and then the water contains in- 

 fusoria in countless numbers, the animalcules forming stripes and clouds in the 

 water; also many rotifers are common, more especially those of the Philodinidce, 

 probably swept down from the mosses on the trunks; yet it is much more remark- 

 able that Copepoda and Ostracoda are very common, the former in the water itself, 

 the latter on the bottom, living on the decaying leaves; the Ostracoda more espe- 

 cially are common; the species hitherto found are Cyclops bisetosus Rehberg, Cyc- 

 lops pulchellus Koch, Candona compressa Brady. I beg Dr. Sven Ekman Upsala to 

 accept my best thanks for the determination. Once I found a few Asellus aqua- 

 ticus in a single hole. In the upper layer of the bottom are found many hitherto 

 undetermined Nematoda, in the lower, various Oligochseta. The greatest and most 

 interesting contingent is yielded by the Insects. 



Very frequent are the larva? of different Chironomidce, further of Ceratopogon 

 and Eristalis (rattle snakes). These larvae, especially, may be present in great num- 

 bers; common are also the larvae of Helodes sp. 



Amid this company we also find the mosquito larva? which, when hatched, give 

 the beautiful mosquito Finlaya yeniculata hitherto unknown in our country and the 

 larva of Anopheles nigripes, mentioned later on. The number of larva? of F. geniculate! 

 found in the holes is always very restricted; often I have only found two or three, 

 commonly about ten, in spring however I have often found fifty and only once 

 about eighty; the larva? are extremely slow and sluggish, difficult to observe in 

 Nature, always seeking back into the darkest parts of the small water volumina or 

 between the leaves; in my aquaria they only rarely come to the surface to breathe, 

 they lie on the bottom or search the bottom for food. When there, they only move 

 forward slowly; the body is commonly held obliquely, and the very short flabella? 

 are in constant motion, brushing off the surface of the bottom; the description and 

 drawings show that the larva differs very much from all other Danish mosquito 

 larva?'; the antenna? are extremely short; the eyes rather small, the anal segment of a 



