22 



AN INTRODUCTION TO ENTOMOLOGY 



when present are simple ocelli; but there may be a group of ocelli 

 on each side of the head. Figure 28 represents a typical centipede. 



Sub-Class NOTOSTIGMA 



Scutigera and its Allies 



In the genus Scuttgera and its allies, 

 which constitute the sub-class Notostigma, 

 there is a very distinctive type of respiratory- 

 organs. There is a single spiracle in each 

 of the spiracle-bearing segments, which are 

 seven in number. These spiracles open in 

 the middle line of the back, each in the hind 

 margin of one of the seven prominent terga 

 cf the body-region. Each spiracle leads into 

 a short sac from which the tracheal tubes 

 extend into the pericardial blood-sinus. 



There are fifteen leg-bearing segments in 

 the body region; but the terga of these 

 segments are reduced to seven by fusion and 

 suppression. 



The eyes differ from those of afl other 

 members of the old group Myriapoda in 

 being compoimd, the ommatidia resembling 

 in structure the ommatidia of the compound 

 eyes of insects. 



The following species is the most familiar 

 representative of the Notostigma. 



The house centipede, Scutigera forceps. — 

 This centipede attracts attention on account 

 of the great length of its appendages 

 (Fig. 30), and the fact that it is often seen, 

 in the regions where it is common, running on the walls of rooms in 

 dwelling houses, where it himts for flies and other insects. It prefers 

 damp situations; in houses it is most frequently foimd in cellars, 

 bathrooms, and closets. Sometimes it becomes very abundant in 

 conservatories, living among the stored pots and about the heating 

 pipes. It is much more common in the South than in the North. 



Fig. 30. — Scutigera forceps. 



