THE CATERPILLAR AND THE MOTH 



the caterpillar, since the insect's brain occupies but a small 

 part of the interior of the head (Fig. 154, Br). From the 

 lower edge of the triangular facial plate (Fig. 152, Clp) is 

 suspended the broad, notched front lip, or labrum (Lm) 

 that hangs as a protective flap over the bases of the jaws. 

 At the sides of the labrum are the very small antennae 

 {Ant) of the caterpillar. On the lower part of each lateral 

 hemisphere of the head are six small simple eyes, or 

 ocelli (0), five in an upper group, and one near the base of 

 the antenna. With all its eyes, however, the caterpillar 



Vent 



Rect 



•An 



Fig. 154. Diagrammatic lengthwise section of a caterpillar, showing the 



principal internal organs, except the tracheal system 



An, anus; Br, brain; Cr, crop; Ht, heart; Int, intestine; Mai, Malpighian tubule 



(two others are cut off near their bases); Mth, mouth; Qe, oesophagus; Phv, 



pharynx; Rect, rectum; SkGl, silk gland; SoeGng, suboesophageal ganglion; Vent, 



stomach, or ventriculus; VNC, ventral nerve cord 



appears to be very nearsighted and gives little evidence of 

 being able to distinguish more than the presence or ab- 

 sence of an object before it, or the difference between light 

 and darkness. Those tent caterpillars that were starving 

 on the denuded tree failed to perceive other food trees in 

 lull leaf only a few feet away. 



The general external form and structure of the tent 

 caterpillar is shown at A of Figure 159. The body is soft 

 and cylindrical. The head is a small, hard-walled capsule 

 attached to the body by a short flexible neck. Back of 

 the head and neck comes first a body region consisting 

 of three segments that bear each a pair of small, jointed 

 legs (Z.); and then comes a long region composed of ten 

 segments supported on five pairs of short, unjointed legs 



[285] 



