PACIFIC FORKTAIL

Ischnura cervula

Pacific Forktail is a common and widespread little damselfly. Only an inch in length, the male is nonetheless easily recognized by the four tiny blue dots atop the black upper surface of the thorax. It frequents aquatic edges – ponds to marshes to drainage ditches – throughout much of the year.

photo (above) 23 July 2006 Salinas wastewater ponds
photo (below) 21 Oct 2006 Lake San Antonio
Beyond the thorax pattern, males (above & below) are characterized by aqua-blue sides to the thorax, black atop the abdomen, and an extensive blue patch on segments 8 & 9, which the blue on top the segments connecting around the sides to the blue undersides. Note also the green lower half to the eyes and around the face. Males have impressive and complex appendages (see Manolis 2003 for details). Among the habitats preferred are small ponds with much duckweed (below).
photo (above) 9 July 2006 Laguna Grande
photo (below) 7 July 2006 Carmel River mouth
While male Pacific Forktails are rather straightforward, the identification of females is complex as they come in two types and change pattern as they age. Of course, when found "in wheel" (left), one can assume that the female is actually a Pacific Forktail!
Female Pacific Forktails typically oviposit alone. This one (below) is depositing eggs well below the surface of the duckweed-topped pond. This is a gynomorphic female that looks quite different than the male, with Army-green sides to the thorax crossed by a thin side stripe.
photo (above) 19 July 2006 Laguna Grande
photo (below) 10 Mar 2007 Laguna Grande

An andromorphic female is more like a male with an aqua-blue and black pattern, but this one (right) is quite young because of the orange spots behind the eye. Note that the "blue tail" (blue patch near end of abdomen) encompasses only the 8th segment in females (males have both 8th & 9th segments blue). Some andromorphic females are almost identical to males; others have a 'dash-and-a-dot' pattern atop the thorax (like an exclamation point), but all have only one abdominal segment blue.

Gynomorphic females have a bewildering array of patterns as they change from immature (below left) to old, dark, pruinose adults (below right). In all cases, though, the abdomen is rather thin and looks long, compared to the shorter, much chunkier abdomen of pruinose female Western Forktails.

Youngsters often have a thorax that is white, tan, pale green, or pale blue, with thin side stripes, but apparently some can even be orange.

Some older females, like this one (above), give me headaches. It is heavily pruinose, including across the top of the thorax, recalling Western, but the abdomen still too slim and long (I still misidentified it). It is sometimes said that Pacific females have white pterostigma while Western have dusky stigmas. This one, however, has a dusky pterostigma. Dennis Paulson (in litt.) advises that while the stigma of Western averages darker — they don't get as ghostly white as many Pacific — in both species the stigma darkens with age. Thus an old Pacific, like this one, can have a dusky pterostigma. Western at the same age should be darker still — it can be black — but determining the age of these little damsels is problematic. So there is another field mark to use with caution.

photo (above left, half page) 6 July 2006 Frog Pond Natural Area
photo (above right, half page) 24 July 2006 Arroyo Seco Lakes
photo (above right, half page) 19 Sep 2006 Laguna Grande

All young female Pacifics, though, apparently have orange spots between the eyes on the back of the head. Very young female Westerns are orange all over.
photo (above) 20 Sep 2006 Laguna Grande

Pacific Forktail is a common and widespread species in MTY, as it is across western North America. The map shows selected locales of specimens or observations, but it likely occurs almost anywhere, at least in the lowlands.

Flight dates in MTY range from 10 March to 2 Dec, one of the longest spans among local odonates. It is often the first ode of the spring. Elsewhere in California, this forktail has been recorded in every month.

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

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Page created 14-15 Mar 2006