60 ENTOMOLOGICAL NEWS [Feb., '15 



was stretched, and above that a layer of cheese-cloth. The 

 edges of both were fastened by stones firmly to the ground on 

 three sides, that of the fourth being held down by the weight 

 of the water into which it extended. A natural habitat was 

 thus secured with grass, water, plenty of room for flight, and 

 sunlight a part of the day. 



Experiment. 



4 p. m., July n. Eight orange females ajnd four males 

 of Ischnura verticalis Say which had emerged in the laboratory 

 July 9 and 10 were placed in the cage. The length of the 

 abdomen of the females was noticeably different and when 

 measured was found to vary from 20.5 mm. to 23 mm., the 

 hind wing varying in length correspondingly. Each day the 

 grass was swept with an insect net, and when the damselflies 

 were removed the catch was put into the cage to supply food. 

 The females were examined daily and the colors noted. Two 

 orange females died and one was drowned within the first 

 four days. 



4 p. m., July 17. One female showed the first indication 

 of change, the bronze black of its abdomen beginning to look 

 dull and velvety. 



9 a. m., July 18. The female noted on July 17 was found 

 dead in the water. Three orange females now remained. On 

 one the black was dull and velvety and the under parts of the 

 head and thorax were greenish. 



3 p. m., July 19. Two females were entirely pruinose and 

 agreed so closely with Williamson's description of the living 

 black female that I can do no better than to quote it. "Bluish 

 or grayish, pruinose; mid-dorsal thoracic and humeral stripes 

 black ; abdominal segments i to 7 with their apices darker, 

 usually black, and 8 to 10 black." The marking on segment 8 

 was a black triangle covering the posterior half of the segment, 

 with the base of the triangle at the apex of the segment. The 

 face, sides of the thorax and under parts were greenish. The 

 pterostigmata of all four wings were brown. When placed in 

 alcohol this specimen agreed entirely with Williamson's de- 

 scription. 



