22 September 2008

Smoky Rubyspot: New county record

One of our tasks this summer was to tag Monarch butterflies at the Detroit River International Wildlife Refuge, mostly the Humbug unit but other Detroit River habitats. Since Point Pelee is such an important migratory stopover for Monarchs, we thought this would be a worthwhile project for the U.S. side of the river. As luck would have it, this has been a spectacularly dismal year for Monarchs. We optimistically ordered two hundred tags, but have only tagged TWO butterflies so far!

Our consolation prize was found at Humbug on Saturday. Stylurus caught this old female damselfly. At first, we weren't sure what it was, although the little white pseudostigma pointed to a broad-winged damsel (Calopterygidae).

It was too dull and narrow-winged to be a jewelwing, leaving us with a rubyspot. We came to the conclusion it was a Smoky Rubyspot, Hetaerina titia, a species with only about 7 other state records, none for our county. I gave it a careful exam, since this is a species we had little experience with. Her thoracic pattern matched, her legs were dark, as was her ovipositor. These characteristics help separate it from the much more common American Rubyspot, H. americana. And the clincher is the spine on the dorsal surface of segment 10, shown in this shot.

Nice scans that help show these featuers can be found online: Smoky Rubyspot here, and American Rubyspot here.

Smoky seems to prefer larger rivers and streams than American. The similarity of the females of both species, and the later flight period of Smoky might indicate they are overlooked in Michigan, but this is probably fairly close to the northern limit of its range. Considering we have never recorded American Rubyspot at Humbug, or any location along the Detroit River, this Smoky Rubyspot was an unexpected find!

3 comments:

Mark said...

GREAT FIND! I have been puzzled why we have seen so few places where they occur --but they do seem to have a later season that H. americana.

John said...

Great record!

Stylurus said...

thanks, Mark and John

I found another interesting dragonfly yesterday and will write a post later.