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 ? 



Exercise 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 antennae, the position of the compound eyes and 

 ocelli and the upper lip, and label them all. 



