NEUROPTERA, EPHEMERIDA, AND ODONATA 121 



FIG. 142. Photograph of a model to show the structure of the honey bee; a, 

 salivary gland ; b, brain ; e, esophagus ; h, honey stomach ; hr, heart with five 

 cross slits through which the blood enters ; t, tongue ; m, mandible ; mx, max- 

 illa ; n, one of the eight ventral ganglia made of nerve cells and connected by 

 white nerve cords ; p, poison gland ; r, rectum or end-portion of the intestine ; 

 rt, aorta or mainblood vessel ; s, true stomach ; st, sting ; t, intestine surrounded 

 by white tubes, the kidneys ; u, ventral head ganglion. 



there are never more than three pairs, are joined to the 

 thorax. All insects having a complete metamorphosis 

 pass through four stages in their life history known as the 

 egg, larva, pupa, and imago. Some forms, such as the 

 Orthoptera, Hemiptera and Odonata, are said to exhibit 

 an incomplete metamorphosis because the difference in 

 form between the larva and pupa is not very marked. The 

 young of these orders is therefore often called a nymph. 

 The larval form of the Lepidoptera is named a caterpillar , 



