22 INVERTEBRATE ZOOLOGY 
MYRIAPODA 
A CHILOPOD. A CENTIPED (Lithobius) 
Myriapods are worm-like animals which live under logs and 
stones, beneath the bark of decaying stumps and trees, and 
in other dark, damp places. The two main groups of myria- 
pods may be easily recognized by the differences in shape and 
habits, — the Chilopoda being flattened and very active animals 
with one pair of legs to a segment, the Diplopoda being usually 
cylindrical animals with short legs, two pairs of which are 
present on'most of the segments. 
Observe the vermiform body, the well-marked segmentation, 
and the segmented legs ; also the lack of specialization among 
the segments, there being no division into thorax and abdomen. 
The animal is plainly an arthropod, but it is not an insect ; it 
is a lower animal than an insect, because its body shows less 
specialization. Note the single pair of antenne and the insect- 
like mouth-parts, also the large hook-like appendages just back of 
the head. These latter are homologous to the first pair of 
legs; they are the principal organs of prehension and are 
provided with poison glands which open on the inner surface 
near the end. Note the anal feelers; these are homologous to 
the hindermost legs and enable the animal to perceive what is 
back of it. 
Exercise 1. Draw an outline of the dorsal aspect of the animal 
on a scale of 5 and label all the organs observed. 
Exercise 2. Draw a ventral view of the head on a scale of 
10, showing the cephalic appendages in position. The 
mouth-parts consist of a pair of mandibles and two pairs 
