126 
Psyche 
[March 
the encounter because its subsequent flight was very erratic. The 
Somatochlora males are very aggressive and will try to grasp any 
other dragonfly — its own species, Cordulia shurtleffi / or even the 
much larger A eschna interrupta. 
Water and air temperatures are relatively low in ponds at high 
altitudes although the diurnal water temperatures are not as low as 
might be expected due to the heat absorbing qualities of the pond 
bottoms and the shallowness of the water. The water temperature 
averages I2°C. (varies from 9 0 to I4°C.) when the larvae first 
emerge in the morning, whereas the air temperatures, which rise very 
rapidly once the sun is up, average 9°C. (vary from 4 0 to I2°C.). 
The night air temperatures drop below freezing and, on many morn- 
ings, frost still lay on the ground when the first larvae appeared. 
The larvae climb up the sedges in areas where the water is seldom 
more than 30 cm deep and usually 3 to 8 cm deep. The larvae start 
to leave the water after sunrise (0700 to 0800 MDT). 
The maximum number of larvae leave the water between 0800 
and 1100 hours (Fig. 4). By 1000 to 1700, they are ready to fly. 
In 1972, observations of undisturbed ponds indicate that 75% or 
more of the tenerals actually leave the ponds between 1100 tnd 1230 
if the weather is fair and the air temperature varies between 16 0 
and i8°C. The initiation of the flights appears to be temperature- 
dependent. On 1 July 1972, flights began at 1100 with an air tem- 
perature of i8°C. The flights stopped abruptly at 1230 when clouds 
covered the sun and the air temperature dropped to I4°C. Flights 
did not resume until 1430 when the sunshine returned and the air 
temperature rose to i6°C. All flights ended for the day at 1500 
When a thunderstorm started and the air temperature dropped to 
I4°C. and below. Any adults which had not flown by this time had 
to remain on the sedges until the following morning. 
Birds are the main predators of Somatochlora during the actual 
transformation process. Spiders and ants will attack larvae near the 
shore but generally account for a very small proportion of the loss. 
Specific data are being assembled for a separate report on bird preda- 
tion and will not be presented here. However, a general summary is 
essential for the present argument. In general, bird predation does 
not begin until the second or third day of emergence. Under normal 
weather conditions, daily loss does not exceed 30 to 50% of the 
*In the studies on drought resistance in Somatochlora larvae, Willey and 
Eiler (1972) misidentified Cordulia shurtleffi larvae for those of Libellula 
quadrimaculata. 
