443 



teneral to full adult coloration is a phenomenon which is not well 

 understood. Just why the thoracic stripes of Bnallagma signatum, 

 for instance, should change from a pale but distinct blue to a bright 

 orange in the course of development, while the stripes of the same 

 region in Lcstcs rcctangularis change from a dull brown to pale blue, 

 is impossible to explain without a more thorough knowledge of the 

 chemical nature of the pigments which undergo the changes. 



The following observations were made upon the emergence of 

 Ischnura verticalis. The rate of development is approximately simi- 

 lar to that of all Coenagrionidae. The rearing-jar was kept in the 

 laboratory on the west side of the building and hence did not get the 

 early morning sun. This accounts for the late emergence of the 



nymph. , . , . , 



9 130 A. M. The nymph crawled out upon the weeds withm the 

 jar and seemed about ready to emerge. The nymph when removed 

 was dissatisfied and restless and tried to get a firm hold on something 

 with its claws. 



9 135. Body nearly dry. 



9:45. The thorax suddenly splits and the insect rapidly emerges 

 from the skin ; color mostly light green and pale yellow ; dorsal por- 

 tion of the eyes dark ; sides of the thorax darker. 



9:50. Clear of the skin; wings 4 mm. in length, abdomen 10 

 mm. ; general color becoming darker ; greens becoming brown ; wings 

 increasing in length; insect restlessly moving about on the support. 



9:55. Eyes plainly striped with brownish bands; abdomen 11 

 mm. in length, wings 4 mm. ; wings suddenly elongating near the 

 proximal end. 



9 : 57- Wings 7 mm. in length. 



10:00. Wings 8 mm., abdomen 12 mm. in length. 



10:01. Wings 9 mm., abdomen 12 mm. in length. 



10:03. Wings 11 mm., abdomen 12 mm.; wings pale light green, 

 thorax and head brownish green ; abdomen pale green at base, darker 

 at apex. 



10:06. Wings 13 mm., abdomen 12 mm. 



10:07. Wings 15 mm., abdomen 12 mm. 



10:09. Wings 15 mm., abdomen 13 mm.; abdomen suddenly 

 elongating at the base. 



10:14. Wings 15 mm., abdomen 15 mm. 



10:18. Wings 15 mm., abdomen 15 mm. 



10:20. Wings 15 mm., abdomen 16 mm. 



10:24. Wings 16 mm., abdomen 20 mm. 



10:28. Wings 16 mm., abdomen 24 mm. 



