A WASP 3 
somite bears a pair of legs on its ventral surface, and the meso- 
and metathorax bear each a pair of wings on the dorsal surface ; 
it is thus in the thorax that the organs of locomotion of the 
animal are concentrated. Find the sutures between the thoracic 
segments. The dorsal cuticula of each thoracic segment is 
called the tergum; the ventral cuticula, the sternum; and that 
of each lateral side, the pleurum. Thus we speak of the pro-, 
meso-, and metasternum, etc. 
In the abdomen the dorsal and the ventral portions of the 
cuticula are composed each of a distinct plate in each somite, 
which are called the tergite and the sternite, respectively. The 
abdomen bears no appendages ; it contains most of the vegeta- 
tive organs of the animal. At its hinder end are the vent or 
anus and, in the female, the sting. Do you find a straight row 
of minute dots on each side of the abdomen and the thorax? 
These are the spiracles, the external openings of the tracheal 
or respiratory system. In dark-colored wasps it may be impos- 
sible to see them with a hand lens, and it may be necessary to 
remove the cuticula from the side of the body and examine 
it under a compound microscope. How many are there on each 
side, and what relation do they bear to the segments? 
Hxercise 1. Draw an outline of the side view of the wasp on a 
scale of 4 or 5, indicating the segmentation and all the 
parts observed. The three thoracic segments may be 
difficult to distinguish at first, but if it be kept in mind 
that each one of them bears a pair of legs, the task will be 
easy. Number on your drawing the thoracic and abdominal 
segments, and carefully label all the different parts and 
organs. 
Exercise 2. Draw an outline of the face on a scale of 10, 
showing exactly the relative length and the segmentation 
of the antenne, the position of the compound eyes and 
ocelli and the upper lip, and label them all. 
