10 INVERTEBRATE ZOOLOGY 



projection. The meso- and metathorax are united immovably 

 with the abdomen and are covered by the two pairs of wings. 

 The anterior or mesothoracic wings are parchment-like and are 

 not functional in flying, but, like the wing-covers of beetles, are 

 held out at right angles to the body during flight. The meta- 

 thoracic wings are membranous and are folded longitudinally 

 like a fan beneath the forward wings, when at rest. Each 

 somite bears a pair of legs on its ventral surface. The cutic- 

 ula of each thoracic somite is composed of a number of 

 distinct plates. Those which constitute the dorsal and the 

 ventral surfaces form the tergum and the sternum of the somite, 

 respectively; those constituting the lateral surfaces form the 

 pleura of the somite. Thus we speak of the pro-, meso-, and 

 metasternum, etc. 



In the abdomen the cuticula of the dorsal and the ventral 

 portions of each somite is composed of a single plate, which is 

 called the tergite and the sternite, respectively. The abdomen is 

 made up of eleven somites, which are not all, however, perfect 

 segments, the sternite of several of the terminal somites being 

 wanting. The posterior end of the abdomen is different in the 

 two sexes, the female possessing an ovipositor, by means of 

 which she buries her eggs in the ground. The sternites of the 

 ninth, tenth, and eleventh somites are wanting in the female, the 

 last sternite being the eighth. Tergites of the three terminal 

 somites are, however, present. Projecting from the hinder end 

 of the abdomen is the ovipositor, which consists of two pairs of 

 short, movable, curved, and pointed structures. One of these 

 pairs is dorsal in position, and the anus is at its base ; the other 

 is ventral, and at its base is the external opening of the 

 oviduct. Extending from the posterior border of the tenth 

 tergite is another pair of pointed projections, called cerci, which 

 may have a sensory function. Just beneath each cercus is a 

 plate called a podical plate. Between the two podical plates on 

 the dorsal side of the animal is the triangular eleventh tergite. 



