821 
No. 145.1 
obliterated after the worm has left it, but remains often for years 
afterwards, and forms a favorite abode for those pseudo-insects 
which are commonly designated sow-bugs or wood-lice. When 
one of these old burrows of the borer is examined, these little 
animals will commonly be found huddled together within it, and 
covering the sides of the cavity as closely as they can stand. And 
on digging around the root of a peach tree at any time several of 
them will commonly be found. As no notice of our American 
species of these creatures has ever been published, that I am 
aware, some account of them may appropriately be given in this 
connection. 
These animals are popularly known in different countries under 
the names of millipedes, wood-lice, hog-lice, slaters or sclaters, 
and sows. In this section “sow bugs” is the popular name in¬ 
variably given to them, whilst the name wood-lice w'ould here be 
understood as designating the wood-tick, Ixodes Jlmeiicanus , and 
its kindred species, and millipede would be regarded as a synonym 
of centipede or “ thousand-legged worm,” a species of Julus or 
Scolopendra. The sow-bugs were ranked as insects by the older 
naturalists, but by most writers at the present day they are 
grouped with the lobster, crab, craw-fish, horse-hoof, &c., in a 
distinct class, which is named Crustacea, in allusion to the hard 
shell-like crustaceous covering which forms the exterior coat 
invmost of the species. They differ from true insects essen¬ 
tially in their breathing apparatus, which is a kind of gills of a 
pyramidal form, and made up of thin plates or short threads 
placed on the under side of the body, commonly at the base of 
the legs. Insects, on the other hand, respite through spiracles or 
breathing pores, placed in a row along eacli side of the body, 
through which, by small pipes, air is admitted into two prino pal 
tubes which run parallel to each other, and are extended the 
whole length of the body. The crustaceans, like insects, have 
jointed antennae and legs, and the body composed of a number of 
segments connected by transverse sutures, but they differ from 
most insects in being destitute of wings, and in undergoing no 
metamorphosis, the young when first hatched having the same 
form and parts which belong to it when mature. In this class 
