I'KIDTHJOK ØKLANI). M.-N. Kl. 



Ill« p.uiicuhirs (ifihc (lisiril)iiiioii in NVjrway are evident from map i and 

 list of localities f^ivcn in lli«- AppcMfJix, and may thus be summed up: the 

 ylnoii (lier is (oiind (lom the \\( -,t oj tli» Kristiania Fjord along the coast 

 to Trondhjem, in a zone about as bivjad as the length of the P'jords. North 

 of the Trondhjeiu Ijoid localizations are scanty, which to a certain extent 

 is due to the lack of investigation, and the most northern locality, as has al- 

 ready been mentioned, is Ribbenesö in Finmarken (70° N. L.). (As to distribu- 

 tion towards the east, see foot-note p. 20). Accordingly the species has 

 not been assigned to the large valleys in the south-east (Österdalen, Gud- 

 brandsdalen, Valdres and Mallingdalen), though 1 have spoken to several 

 persons who are of the opinion that they have seen it there. But as con- 

 fusion with the large black Liiiiax cincreo-nigcr Wolf is not out of the 

 question, these assertions need verification. 



In Norway Arion ater is not met with at any great altitude. I have col- 

 lected it at Opset (between Finse and Voss), 850 m. above the level of the sea. 



Bionomics. When night conies on, or the weather is cloudy, Avion 

 ater may be seen in large numbers on the roads, in meadows, and in 

 forests too, though less frequendy in forests of conifers. It only rarely 

 leaves the ground to crawl on bushes. According to its appearance in 

 rain}' weather — from which it gets the name "regnorm", — it is often 

 said to predict rain. 



It is eminently omniphagous, feeding on all kinds of soft vegetable 

 matter, not rarely being seen on fungi, and also devours the dead bodies 

 of small animals. As Wotton (1893) states, it may do without solid food 

 for weeks if only sufficient moisture is present. 



In Norway the parasites of this species have not been subject to close 

 investigations, but it may be mentioned that 1 have recorded one of the 

 most interesting, viz. Lcptodcra appvndiciilata Schneider. This nematode, 

 belonging to the family of Angiiillnlidae, was found by the present author 

 in specimens from Osterö in the neighbourhood of Bergen and from Tromö 

 near Arendal. Undoubtedly this is merely an indication of a considerable 

 distribution in this country ^ 



KüNKEL (1916) and Adams (19 10) have published good observations 

 concerning the copulation, and I may be allowed to sum up the results of 

 these. I have only found Arion ater copulating a few times, always in 



' Concerning this nematode the following facts may be mentioned (Claus 1868). In the 

 slug the little worms (i — 2 mm.) are enclosed in the anterior part of the foot-sole, 

 especially to both sides, and at this stage are distinguished by two long cuticular rib- 

 bons on their posterior part ; they have neither mouth nor anus, and are sexual 

 dimorphous, the female being longer than the male. Later on they make their way 

 from the foot, and when for instance the slug is placed into water, it may easely be 

 seen that they creep out. In the ground they quickly attain maturity, and then several 

 free-living generations, perhaps of indemnité number, succeed each other, all of them 

 smaller than the parasitical one. At last some specimens will enter an Arion ater, 

 where they are said first to occur in the blood-vessels. 



