CHAPTER XVIII 
TRACHEATA 
Cuass II]. MYRIAPODA 
Chilopoda—Lithobius, Scolopendra, Scutigera. 
MrEraropa Diplopoda (Chilognatha)—Julus, Polyxenus, Pawropus. 
CHARACTERISTICS.—Tvracheate Arthropoda with a distinct head 
and a number of similar somites ; no distinction of thorax 
and abdomen. A pair of antennae, mandibles, and maxillae, 
and numerous six- or seven-jointed clawed legs present. 
Of all the Tracheata, with the exception of Peripatus, the 
Myriapoda exhibit least signs of specialisation in their external 
structure. The segments posterior to the head, which in the 
GEOPHILIDAE may amount to some hundreds, are all very 
similar, and they are not externally grouped together into any 
regions such as thorax or abdomen. 
The Myriapoda are divided into two orders : (i.) the Chilo- 
poda and (ii.) the Diplopoda or the Chilognatha. 
Order 1. CHILOPODA. 
CHARACTERISTICS. — Myriapoda with dorso-ventrally compressed 
body. Antennae long, with many segments. The second parr 
of postoral limbs form the poison claws. One sternum and 
one pair of legs to each segment. Genital orifice posterior. 
Stigmata lateral, tracheae branching and anastomosing. 
Lithobius forficatus is the commonest English centipede ; it 
is found all over Europe, in the summer living under stones, 
leaves, etc., and in the winter hiding itself in the earth. It is 
about one to one and a half inch long, and of a chestnut- 
