THE CONCHOLOGIST, 



C. alba. Barmouth. 



Utriculus obtusus. Barmouth or Mochras. 



Actaeon tornatilis. Mochras, Harlech. 



Barmouth, Portmadoc, Beaumaris. 

 Scaphander lignarius. Penmaenmawr, 



Barmouth, Beaumaris. 

 Philine aperta. Barmouth. 

 Melampus myosotes. Aberavon. 



The number of species enumerated in this 

 list is 135, and 19 varieties. 



SLUGS AND FROST. 



By E. I. Lowe, F.K.S., &c. 



IT has been noticed that excessively cold 

 winters, instead of (as generally supposed) 

 destroying slugs, have a contrary effect, and 

 this is very noticeable at the present time. 

 A less frost with mild intervals, inducing the 

 slugs to leave their winter quarters, would be 

 more destructive than a continuous frost. 



When the late frost commenced, the slugs 

 congregated under leaves (good resisters of 

 cold), but as the severity increased they dis- 

 appeared, descending deeper and deeper into 

 worm holes, &c., where they would find a 

 warmer temperature, but, now the frost has 

 ceased, they are again on the surface, ap- 

 parently with no diminution in their numbers. 



The following records bearing on this 

 subject will be instructive. In the frost of 

 1860-61, and again in that of 1879-80, some 

 experiments were made as regards the amount 

 of frost sufficient to kill slugs, &c. These 

 may be briefly stated. A bell-glass was 

 placed on a slate, under which were Arioti 

 ater, Limax favus, L. maximns, L. agrestis, 



and Amalia inargitmta* When the tempera- 

 ture fell to 14°, the slugs were frozen and 

 stiff, and not one recovered, so that 18° 

 of frost is enough to destroy their lives. 

 Helix aspersa, under another glass, survived ; 

 it, like other non-operculated slugs, had a 

 covering of a light layer of mucus (impreg- 

 nated with calcareous salts), which had the 

 power of resisting many degrees of frost, for 

 as salt water requires a greater degree of 

 cold to freeze it than fresh water, no doubt 

 this layer of mucus was a sufficient protec- 

 tion. The common gnat {Culex pipiens), 

 and larva of the weevil {Ctirciilis sulcatus), 

 were similarly treated, and when the tempera- 

 ture fell to 20° (12° of frost), the gnats fell 

 dead, and the weevil larva became frozen and 

 perished. 



Frost will, with difficulty, penetrate organic 

 soil and decomposing leaves. At Highfield 

 House, near Nottingham, in the great frost of 

 1860-61, when the temperature fell to 8° below- 

 zero at four feet above the ground, and to 

 13-8'' below zero on the grass — a drain, cut 

 through a bed of organic soil (mainly com- 

 posed of nut branches), had a temperature 

 four inches below^ the surface, of 42° above 

 zero, i.e. 55*8° higher than on the grass at a 

 few yards distance. Although the river Trent 

 was frozen, this drain, only one foot wide, 

 and containing less than twelve inches (in 

 depth) of water, remained unfrozen, the heat 

 of this ancient bed of organic matter keeping 

 off frost. Here Li/iiax Icevis was found, under 

 pieces of wood, regardless of the great cold. 



The temperature at different depths in the 

 ground, and the time occupied in reaching those 

 depths is an interesting enquiry, for we find 



* On reporting these experiments to my friend, the late Dr. 

 Gwyn Jeffreys, his attention was called to peculiarities in the 

 animal of the members of the Liitia.x family that did not exist in 

 Ajnalia inarginata, but he thought they were not sufficient to 

 warrant the adoption of a separate genus {or Amalia inarginaia 

 and gagates. More recently, the great difference observed in the 

 time occupied in coition, viz. : — only forty seconds with Limax 

 agrestis, and from six to eight hours with Amalia marginaia, 

 seems to be a convincing proof that these two slugs cannot belong 

 to the same genus. 



