178 ARTHROPODA. 



2. The following appendages will be found : 



(a) The chelicerce. What is their structure? Are they 

 armed with pincers? 



(6) Four pairs of long walking legs. How many segments 

 have they? The viscera extends into the bases of these appen- 

 dages. 



(c) The male is provided with a pair of ventral appendages 

 called the ovigerous legs, by means of which the eggs are collected 

 as they are laid by the female. These appendages are not present 

 in the female. 



Make a drawing of the under side of a specimen. 



Cole: Pycnogonidia of the West Coast of North America. Harriman 

 Alaska Exped., 10, 1904. 



MYRIAPODA. 



LITHOBIUS. (Centipede, Earwig.) 



These animals may frequently be found under stones, logs 

 or boards, or about rubbish or manure heaps. They live largely 

 on insects, larvae, and small worms, and are very active. 



1. Notice the shape of the body and count the number of 

 segments. Is there a distinct head? Are the segments very 

 movable? 



2. How many appendages does each segment possess? Are 

 all of the segments provided with appendages? Allow the ani- 

 mal to run and see how the legs are used. Do those of a side all 

 move in the same direction at the same time? Are all of the 

 legs alike? Notice the pair of appendages just behind the head 

 and see how they differ from the others. These appendages are 

 organs of prehension that are used in grasping the prey. They 

 are provided with poison glands that open on their inner sides 

 near their free ends. 



3. Examine the head and find the eyes, antennae, and mouth 

 parts. The latter consist of a labrum, a pair of mandibles, and 

 two pairs of maxillce, the last pair of which are united to form a 

 labium. 



