1974] 
Willey — Subalpine Dragonfly 
13 
nocturnal or early morning emerging populations. Teneral adults 
which fly up during the middle of the day are subject to harassment 
and possible damage from the reproductive males. However, by the 
time the first Somatochlora reproductives return to the Colorado 
ponds, 95 to 100% of the annual production of tenerals have already 
left the pond (Figs. 2 and 3). The diurnally temporal separation 
of the reproductives and the nocturnal or early morning tenerals of 
the lower altitudes has been replaced by the seasonal separation of a 
1 to 2 week teneral maturation period during which time the dragon- 
flies fly in the forest away from the ponds while the remainder of the 
population is emerging. The high altitude ponds of Colorado seem 
to be sufficiently isolated from each other to keep recruitment of 
reproductives from lower, and therefore earlier, ponds to a minimum. 
The diurnally transforming dragonflies are also exposed to preda- 
tion by birds. The highly synchronized emergence of Somatochlora, 
however, provides that the relatively large number of larvae which 
emerge during the first few days ensure that many tenerals get away 
from the pond. To what extent a synchrony of emergence provides 
selective advantage to the dragonfly population by ( 1 ) partially fore- 
stalling the results of a revised predator searching image and/or 
shift in prey preference or (2) saturating the environment with prey 
with a resulting early satiation of the predators is as yet undeter- 
mined. It is likely that both predation tactics are involved and 
thwarted by this mechanism. 
Summary 
Somatochlora semicircular is has been able to adapt to the rigors of 
the subalpine and lower alpine habitats of Colorado. The corduliid 
tendency toward a flexible, early morning emergence pattern has con- 
tributed to its shift to a full diurnal emergence pattern. In addition, 
it may be able to initiate emergence at relatively low water and air 
temperatures. The emergence pattern has been strongly synchronized, 
shortened and restricted to a single seasonal peak, possibly as a result 
of ponds drying up early in the season at high altitudes, predation 
pressure, which may be the same or worse than that at lower alti- 
tudes, and the effects of potential interference between the aggressive 
reproductive males and the soft-cuticled teneral adults. 
Acknowledgements 
I wish to thank Dr. Robert B. Willey for constant advice and 
encouragement. I appreciate the valuable critical reviews by Drs. 
