The Dragonflies
(Insecta: Odonata)
of the Columbia Basin, British Columbia:
Field Surveys, Collections Development and Public Education
Table
of Contents
Return to Family Gomphidae
Gomphus Leach
Gomphos means bolt in Greek, and refers to
the similarity of the shape of the dragonfly's body to the arrow
of a crossbow. This is an old and frequent allusion in the English
language. The genus is a large one, but only a single, rare species
enters British Columbia in the extreme south.
Gomphus graslinellus
Walsh*
Pronghorn Clubtail
|
 |
Provincial Status
CDC rank: S2
Red List
Gomphus graslinellus is a rare species of warm lakeshores and
streams in a few valleys in southern British Columbia. Columbia-Kootenay
Distribution
In the Kootenays G. graslinellus is known only from Christina
and Wasa lakes. Dean Nicholson, a project volunteer, discovered
the Wasa Lake population in 1998. The Christina Lake population
was known in Whitehouse's day (Whitehouse 1941) and a male was photographed
there in 1980 (G. Doerksen, RBCM collection), but we did not find
the species during the 1998/1999 survey. It probably still lives
around Christina Lake; the early-season collecting there in 1999
was hampered by inclement weather.
Global Distribution
Southern British Columbia east to Ontario; south to Ohio, Texas
and Washington State (Bick and Mauffray 2000). Faunal element: Transition
(see Appendix 2).
Biological Information
The larvae burrow in the sand and silt along wave-washed shores,
and when ready to emerge, they crawl only a few inches away from
the edge of the water on the sand or gravel where they metamorphose.
The adults bask on sunny beaches, roads and paths near the water.
They have a characteristic undulating flight. Kootenay dates range
from 3 June to 20 July; the recorded flight period in British Columbia
is 3 June to 25 July (Cannings and Stuart 1977, present study).
Management and Protection Considerations
More precise knowledge of larval distribution would assist in making
decisions bearing on the health of G. graslinellus and other
lacustrine species -- but its shoreline habitat is often shared
with intensive human recreation use. Marina developments, pollution
from power boats and popular swimming beaches all have potential
impact on larval survival. The areas around Christina Lake where
Whitehouse (1941) found G. graslinellus in 1921 and 1938
have been developed with vacation homes and marinas. Any remaining
natural beaches should be protected where possible. In the riverine
environment, the impact of introduced predatory fish (especially
bass) on this scarce dragonfly is also of concern, but no data concerning
this situation are available.
|
