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. 
