300 MOLLUSCA. 



fields in Britain. Like all slugs, its life is dependent on moisture. 

 In dry weather it gets under stones, &c., and comes out only at 

 night to feed. The body is spindle-shaped and ashy-grey in 

 hue, with a reddish or yellowish tinge, sometimes mottled ; the 

 foot has pale sides, and the shield is large. The oval shell is very 

 thin, and marked mth indistinct lines of growth with a broad 

 membranous margin. It exudes great quantities of slime, and is 

 most prolific. Seven or eight separate batches of fifty ova each 



Fig. 174.— Grey Field-sluo {Agrioliriiax agrestis). Slightly enlarged. 



are laid during the breeding season, which is from May to 

 November. The little ova are laid in heaps of six to fifteen 

 in the ground and under moss, especially during August, 

 September, and October. They take three weeks to develop; 

 the adults live many years. In the winter they may be found 

 under stones and rubbish in a semi-torpid state. All kinds of 

 plants are more or less attacked by them. It is chiefly in damp 

 weather that slugs are destructive. 



Another species is the Black-striped Slug (L. maxitmis), which 

 sometimes reaches seven inches in length. Although not very 

 prolific, it does much harm. The ova are deposited in heaps, 

 joined together with a gummy sKme, during the autumn. These 

 slugs vary much in colour : some are black, others yellowish, 

 spotted with black and white ; the foot is always edged with 

 white, and the slime is always iridescent when dry, white when 

 fresh. 



The common Black Slug (Arion afcr) is about four inches 

 long. It varies from black to red, yellow, dark-green, or brown, 

 and is covered with prominent tubercles, much contracted in 

 front and pointed behind ; the foot has a yellowish border, and 



