Ophiogomphus bison
In the spring, along rushing rivers cascading out of the Santa Lucia Mountains, a lucky observer might find one of the most fascinating odes in Monterey County: the Bison Snaketail. Males sit on rocks out in the rapids (below) but only the female has the tiny pair of bison-like 'horns' atop the head (above).

Bison Snaketail is one of four species of snaketail in California, but the only one in MTY. Males have expanded 'clublike' tips to the abdomen (like a cobra hood) and the abdomen is a colorful yellow and black. Bison Snaketail has a bright green throax with a broad dark-brown stripe across the side. Males sit on rocks in the current, waiting for females or disputing other males, often with raised abdomens.

Before 2007, there were only two records of Bison Snaketail in Monterey County. P.H. Arnaud, Jr., collected singles on successive days at "Big Sur State Park" on 19 & 20 June 1949. It is assumed this was Pfeiffer-Big Sur State Park, and presumably the snaketails were along the Big Sur River. The first one, a female in poor condition on 19 June 1949, is now #8934 in the collection at Illinois State University. The second is now held at the California Academy of Sciences, San Francisco. [Thanks toTim Cashatt, curator at Illinois State Univ., and Tim Manolis for these details.]

In Apr-May 2007, populations of Bison Snaketail were discovered along the Arroyo Seco and upper San Antonio Rivers (D. Roberson et al.). The species may be present along all the major rivers running out of the Santa Lucia Mountains.

Photos of males (above) 28 Apr & 5 May 2007 Arroyo Seco River
Photos of female (below) 12 May 2007 North fork San Antonio River

Females may occur rather far from water, perched in the woods (like this one left, above, and below). They have a gorgeous pattern of yellow, green, and brown to go with the yellow face and gray eyes. Females have the tiny pair of 'horns' atop the head for which this species is named. In a very close look (the top photo on this page), note that each 'horn' is topped with black although the base and 'platform' for the 'horns' is bright orange-yellow.

A character of snaketails that helps to distinguishe them from Pacific Clubtail, which can occur in the same habitat, is the pale stripe on the thighs of the rear legs. The clubtail has all-black legs.

The map shows the currently known locations for Bison Snaketail in MTY: along the Big Sur, Arroyo Seco, and upper San Antonio rivers. The Big Sur specimens were back in 949, so whether they still occur there is not yet known. The species occurs on gravel bars in rivers throughout the foothills of both the Sierran and Coast ranges of northern California. MTY is its southernmost known locale in the Coast Range [it occurs south to Tulare Co. in the Sierra Nevada].

Though flight dates ranges from April-October, it is said to be most common from May to July (Manolis 2003). The known dates in MTY are 28 Apr-20 June.

Literature cited:
  • Manolis, T. 2003. Dragonflies and Damselflies of California. Univ. of Calif. Press, Berkeley.
Web resources:
Major identification web sites with much information on California odes include: For sites with excellent photos to compare for identification or to simply enjoy, see: Many of these sites have links to other useful pages. Kathy Biggs's site is particularly useful in her selection of links.

All photos © Don Roberson 2007


Page created 8 Mar 2007, updated 16 May 2007