62 A CENTIPED. 



into thorax and abdomen ? Count the segments. The number 

 is sometimes of importance in classification. 



b) Examine the legs. Do they differ in any respect except that of 



size ? How many joints in a leg ? The number of pairs should 

 correspond exactly to the number of trunk segments. What is 

 the function of the single claw on the end of each leg and of the 

 spines on some of the joints ? 



c) The legs of the hindermost segment are modified into a pair of 



anal feelers, probably to enable the animal to perceive what is 

 back of it. 



d) Examine now the modified front pair of legs, sometimes called 



maxillipeds. These curve forward so as to act with the mouth 

 parts and terminate each in a strong claw traversed by a duct 

 leading to a poison gland. The opening of the poison duct is 

 near the tip of the claw, but you may not be able to find it. Con- 

 trary to popular opinion, the claws of the other legs are not poison- 

 ous. 



e) Determine the number of joints hi the antennas projecting from the 



front of the head. This point is also sometimes useful in classify- 

 ing the species. 



f) Just back of the antennae are the eyes. Study these carefully. 



They seem to be simply groups of ocelli. Determine the number 

 of ocelli for the species you have in hand. Is the number constant 

 for all the specimens used in the class ? In one genus, at least, 

 the eyes are rudimentary not sufficiently developed for vision. 

 How is this fact correlated with the habits of Centipeds? The 

 House Centiped Scutigera has compound eyes. 



Exercise i . Draw the entire animal, dorsal view, if necessary enlarging 

 enough to make the sketch four or five inches in length. 



g) Study the under side of the head. There is a more or less movable 



upper lip, labrum, and three pairs of mouth parts proper, not 

 including the poison jaws. The last pair of these, most posterior, 

 is the second maxillae. They lie just in front of the poison 

 jaws, their palps projecting far enough to be easily distinguished. 



