58 INSECT BEHAVIOR 



where it acts as a solid plug. When the waste matter is expelled the 

 grub often loses its original color, which is due only to the sewage 

 showing through its transparent skin. In the case of the shell-wasp, 

 it changes from a clouded honey color to white, slightly tinged with 

 yellow. It also becomes more opaque. 



Ten days after excretion the insect pupates. Then comes another 

 wait of three weeks before the final wasp issues from its cell. 



During these twenty-one days, the pupa receives its finishing 

 touches at first, when the transformation from the larval state takes 

 place, there is no dark pigment in the body. It is yellowish white 

 and rather translucent. Color appears first in the eyes, which turn 

 light lavender, then brown and finally black. Next, the pigment ap- 

 pears in the remainder of the head. Then, as though coming through 

 some hidden tunnel below the flesh, it appears as a mere dot of dark 

 fluid in the center of the thorax. Slowly the dot expands, throwing 

 out arms of color which later combine and fill the entire thorax with 

 pigment, like a rocket that unfolds its display in the sky. Next the 

 slender petiole of the abdomen becomes clouded. This soon gives 

 place to darker color while its recent cloudiness appears in the abdo- 

 men itself. At length the entire insect turns black save for the three 

 small orange -yellow patches on its abdomen. 



This general dullness is due to the pupal skin in which the finished 

 wasp is now resting. We see it through this delicate membranous 

 covering which is immeasurably thin, and fits the insect as closely 

 as her own external skeleton. Under the transparent covering the 

 insect appears dull, but otherwise quite normal except for her wings. 

 Her legs and antennae are of proper length, her head and body neatly 

 proportioned, yet her wings are but a third the natural size. They 

 are hollow appendages intricately folded and held in place by the 

 wing bags of the membranous covering. Later with the pupal skin 

 of which they are a part, these bags are shed, releasing the true wings, 



