26 Trans. Acad. Sci. of St. Louis. 



upon the European species point to the conclusion that 

 it does afford protection. 



One wonders about the value of protective coloration 

 when one sees a dark gray female, resting on a green 

 tamarack, very conspicuous indeed, greedily devouring 

 one which is green. But again in contrast to this, when 

 the green nymphs are at rest on the clematis or hop 

 vines and an attempt at their capture is made, they dart 

 from leaf to leaf, quickly turning to the under side, then 

 drop to another and vanish in less time than it takes to 

 tell. 



Color Change. 



We have seen in the chapter on the moulting process 

 that the insects at hatching are all alike of a light yellow 

 color. Just after the first real ecdysis they occur in 

 many colors, the two extremes being distinct green and 

 dark brown. We have seen that green insects gradually 

 change to brown ;^=^ this may be due to the color of the 

 environment. My attention was first attracted to this 

 by the following observations upon nymphs and adult 

 females which were kept for other notes. 



In the first instance the cage contained no potted 

 grass nor green things of any kind, and the insects could 

 rest upon nothing but the almost black wire screening of 

 the cage. It seemed to me that the ventral surface of 

 this adult female — the part in constant contact with the 

 screening — became darker from day to day. Whether 

 this happened on account of the environment or in mere 

 coincidence is not known, but we must not fail to con- 

 sider that this was a full-grown, winged insect when 

 placed here. 



In the second case the adult insect when placed in the 

 cage was entirely green, both body and wing. After 

 being there for thirty-four days until its death, we found 

 the wings and the abdomen under the wings still green, 



" See pages 15, 16. 



