1974] 
Willey — Subalpine Dragonfly 
129 
c 
Figure 4. Daily emergence pattern of S. semicircularis on 2 July 1970 
at Irwin Pond South. Lower curve shows the number of nymphs leaving 
the water (solid line) and transformed teneral adults ready to fly (dashed 
line) at successive hours during the day. Middle curve shows water tem- 
perature 3 cm below the surface at two separate stations, 1 m apart, and 
air temperature 45 cm above the surface of the water in the emergence 
area. Top curve shows solar radiation. Nymphs recorded here completed 
the entire transformation process successfully. 
