304 THE SCOTTISH NATURALIST 



this genus. On Exmoor he states he found none in the 

 open^ though other forms were present under " nine out of 

 every ten stones that he turned over, and here the smaller 

 species of ants also abounded." Close to stone walls, 

 however, the Armadillidia only were found ; and this was 

 thought to be due to the presence of swarms of the large 

 wood-ants, which he thought would attack and destroy any 

 species of woodlice that could not protect themselves by 

 rolling up. 



Relation to Habitat, etc. — Woodlice respond very quickly 

 to light, heat, varying weather conditions, etc. In the early 

 spring, when dusk, I have observed Oniscus asellus and 

 Porcellio sender in large numbers making their way from 

 outhouses into the garden. 



Pierce records that on "25th May, at 7.30 A.M., a large 

 number of sow-bugs had gathered at baits. At 8 o'clock a 

 sudden storm commenced to rise. The sow-bugs seemed 

 immediately conscious of the danger and hastened in all 

 directions for the highest shelter possible, gathering protec- 

 tion on the fence and beneath the clapboards of the house. 

 All were out of sight when the first drops of water fell. In 

 April and May there was considerable rain, and during the 

 periods of sunshine, at whatever time of day, the sow-bugs 

 were to be seen everywhere crawling over the side-walks and 

 pavements. 23rd and 24th April the ground was drenched 

 with water, and on the 25th dead sow-bugs were to be found 

 everywhere on the ground and on the side-walks. On 

 3rd June a similar observation was made in a spot where 

 the water had stood for several days. By 15th June the 

 intense heat had driven the sow-bugs from the open, so that 

 few could be found in unprotected places." 



Specimens of Porcellio scaber which had been kept in 

 water for a few minutes were noticed on being placed on 

 a piece of brick to at once commence a rhythmic movement 

 of the abdomen, raising and lowering it at the rate of about 

 forty-five times per minute. If placed upon a piece of 

 blotting-paper on being removed from the water, this 

 movement does not take place. 



Mr P. A. Aubin (20th October 1913) writes : — " If P. Icsvis 



