128 LI MAC I DAE 



Family LIMACIDAE 



The snails considered in the preceding pages have spiral 

 shells which are large enough to retain all or nearly all of the 

 contracted animal. However, several species of snails called 

 slugs have little or no external shell. In one family found in 

 Illinois, the Limacidae, a thin, shelly, non-spiral plate of cal- 

 careous matter acts as a partial protection to the lung. 



A characteristic of all slugs is the ability of the animal to 

 exude quantities of mucus when it is disturbed. This mucus 

 is so tenacious that with it the animal may suspend itself from 

 a bush or weed and even descend to the ground, much as some 

 caterpillars do with their silken thread. 



Most of the native slugs found in Illinois are small and 

 inconspicuous, but in the states bordering the Pacific Ocean 

 occur several species belonging to the family Arionidae which 

 attain a length of nearly 6 inches. The largest species, Ariolimax 

 columbianus (Gould), is of a greenish yellow color, sometimes 

 with irregular purplish blotches. Philomycus carolinianus, which 

 is very common in Illinois, is the nearest approach in size to 

 this western giant among slugs. 



In the Limacidae, the long and narrow body is somewhat 

 humped toward the middle and front end, where a rounded 

 projection called the mantle covers the lung region. The eye 

 peduncles are long, rounded and tapering. The tentacles are 

 very short. The body is covered with elongated tubercles sepa- 

 rated by shallow^ furrows, which are often marked by color 

 lines. The tail or posterior part of the animal tapers to a point; 

 the upper side of the tail is carinated near the end. At the edge 

 of the mantle, near the posterior end, animals of the family 

 Limacidae have a small opening, which is the breathing pore 

 or orifice. 



The small Limacidae are vegetable feeders, eating decaying 

 vegetation, as well as healthy plants. 



Genus DEROCERAS Rafinesque 



The genus Deroceras includes small Limacidae not exceed- 

 ing 2 inches in length. In slugs of this genus, the mantle covers 

 only a small portion of the long, narrow body. 



Deroceras has long been known under the name Agriolimax, 



