HARDWICKE'S SCIENCE-GOSSIP. 



271 



what tribe, then, does it belong ? Many of our 

 readers will doubtless be surprised to learn, that the 

 crawling thing they have always considered as an 

 insect is in reality a crustacean ; that is to say, it 

 belongs to the large family of crabs, and is a cousin, 

 though a distant one, of the little creatures whose odd 

 sideway movements in the rock -pools left by the 

 retreating tide are the delight of children at the 

 seaside. 



At least three species of woodlouse are common in 

 England, yet few people, except naturalists, know 

 how to distinguish them. The first and perhaps most 

 generally known is the "pill-woodlouse," the scien- 

 tific name of which is Armadillo vulgaris, in allusion 

 to the odd likeness it bears with its hard shelly 

 covering to the armoured quadruped so-named. The 

 pill-woodlouse seems really clad in mail, for the 

 horny surface of its carapace has the bluish gleam of 

 steel, and is as polished as a knight's cuirass. More- 

 over the armour of the woodlouse is even superior, in 

 point of make, to a perfect suit of harness finished 

 by the hand of the most skilled of ancient armourers. 

 For it is so cleverly jointed, that it not only does not 

 interfere in the least with the free movements of its 

 owner, but it actually enables the latter to roll him- 

 self into a ball, each segment fitting one into the 

 other and presenting a shining impervious sphere to 

 the attacks of every enemy. Its striking resemblance, 

 when thus coiled up, to a pill, has given to the 

 woodlouse its English name, and it is said that in the 

 earlier days of medicine they were actually used by 

 druggists. How this may be we know not, but 

 certain it is that they have been employed by many 

 a schoolboy in very unpleasant practical jokes. 



The second species, the common woodlouse 

 (Porcellio scaber), is devoid of this ability to roll 

 itself up, and this constitutes one of the differences 

 between it and the first-named. The colour is much 

 the same as that of the pill-woodlouse ; but it is not 

 nearly so polished, and is sometimes spotted with 

 white. The chief mark, however, by which the two 

 species may be distinguished, is the projection in the 

 common woodlouse of the abdominal appendages 

 beyond the carapace. In the pill-woodlouse these do 

 not appear. 



The third species is the land-slater (Onisats asellus), 

 and this kind also does not roll up. This woodlouse 

 is known by its having eight joints in the antennae, 

 whereas the others have only seven. It has also two 

 rows of yellow spots, and the same number of white 

 spots along the back. All the species have seven 

 pairs of legs, equally developed. 



Woodlice, like other crustaceans, breathe air by 

 gills ; but it is essential to their well-being that the 

 air they breathe should be saturated with moisture. 

 Accordingly, they never object to shelter under a 

 stone, otherwise conveniently situated, on the score 

 of its being too damp, though they occasionally 

 prefer, as a refuge, a rotten log, or some other piece 



of decaying timber. Damp and darkness are their 

 delight, and the light of day is hateful to them ; they 

 will take advantage of any retreat to avoid it. Hence 

 they are sometimes found in the galleried nests of the 

 hill-ant (Formica ritfa), where its hosts do not 

 interfere with it, and, indeed, seldom take any notice 

 of this uninvited guest. 



Their food is chiefly of a vegetable nature, and as 

 they are very sharp-toothed little creatures, they are 

 rather destructive in gardens, and where they abound 

 it is not easy to get rid of them. Fowls will eat 

 them readily, and when woodlice are too plentiful, 

 the inhabitants of the hen-house may be let loose 

 upon them with great effect ; only that in a well-kept 

 garden we are apt on such occasions to find — as the 

 ancient Britons found when they called upon the 

 Romans to fight their battles for them — the invaders 

 more formidable enemies than those they were 

 intended to drive out. 



In the order Isopoda, to which woodlice belong, 

 the young are developed within a larval membrane, 

 and when they are liberated by the bursting of the 

 membrane, they nearly resemble the adult, with the 

 exception of having only six pairs of legs instead of 

 seven. The respiratory system is curious. The seat 

 of the organs of respiration is the lower surface of 

 the abdomen, these organs consisting of leaf-like 

 branchiae, or gills, protected by plates folding over 

 them. 



Woodlice are not by any means the only creatures 

 to be found under stones. Almost as common, 

 perhaps, as these are the millepedes, strange little 

 beings, in appearance something between a hard- 

 bodied caterpillar and a centipede. These are some- 

 times called "wire worms," but quite erroneously, 

 the real wire-worm being the larva of the click-beetle 

 (Elater). Their bodies are perfectly cylindrical ; 

 they are generally from an inch to an inch-and-a-half 

 in length, and though they have not really a thousand 

 legs, as their name implies, they have a goodly 

 number, namely, from a hundred and sixty to two 

 hundred. These feet look almost like a fringe of 

 delicate white hairs, and, as the millepede glides 

 along, the movement of its many legs imparts a kind 

 of rhythmic wave-like motion to its whole body, which 

 is pretty to watch. 



Three species are common in England. The first, 

 and perhaps best known, is called Julns sabulosus ; 

 its colour is dark greyish-brown, with two reddish lines 

 running down the back. The common millepede 

 (Jitlus terrestris) is the second species, a little 

 smaller than the first, and distinguished from it by 

 lacking the two reddish dorsal lines. The third 

 species (Glomeris marginata) is sometimes called 

 the "pill-millepede," and is even mistaken for the 

 pill-woodlouse, from its habit of rolling itself up 

 spherically. The other millepedes roll themselves 

 also when touched or disturbed, but in a flat spiral, 

 like a coil of wire. The pill-millepede may really 



