262 



ORDER ISOPODA ; LIMNORIA, WOOD-LOUSE. 



and producing an evident swelling externally. Between eight 

 and nine hundred young ones have been observed beneath the 

 body of a single female ; and the parent has the instinct to set 

 them free in situations frequented by the Prawns. Of those 

 marine Isopods which are not parasitic, the most worthy of notice 

 is the Limnoria terelrans ; which, although not more than a 

 sixth of an inch in length, is, through its boring habits, and its 

 powers of multiplication, exceedingly destructive. It pierces 

 timber in different directions with astonishing rapidity, appa- 

 rently for the purpose of feeding upon it, as in its stomach are 

 found minute particles of the wood. It is found in different 

 parts of the British Ocean, attacking wooden piles, immersed in 

 water, in our dock-yards, bridges, flood-gates, chain-piers, &c. ; 

 and perforating them in the most alarming manner. 



799. It is in the terrestrial species, that we find the most 

 remarkable provision for the inclosure of the respiratory organs ; 

 these being completely folded over, by plates developed from the 



abdominal members ; and 

 the anterior plates being 

 perforated with a row of 

 small holes, through which 

 the air gains access to the 

 gills within. Like the Land 

 Crabs, these terrestrial Iso- 

 pods (of which the common 

 Wood-louse is a very familiar 

 example), for the most part 

 frequent damp situations; 

 inhabiting dark and con- 1 

 cealed places, such as cellars, \ > 

 caves, holes in walls, the un- 

 der-side of stones, &c. They feed upon decaying animal and vege- 

 table matter, and come forth from their retreat in damp weather. 

 They crawl slowly, except when alarmed ; and they have the 

 power of rolling themselves into a ball, so as to expose on the 

 outside nothing but the plates of the back, and to conceal the 

 appendages of the underside of the body. 



FIG. 486. ARMADILLO 



PUSTULATUS. 



FIG. 485. ANILOCRA. 



