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A CPIE Notebook Project – Keys to Aquatic Biota of Hawai‘i Page I14
 
Key to Hawaiian Damselflies (Odonata)1

CPIE Aquatic Environments
Near Links: [ALGAE] | [HIGHER PLANTS] | [OTHER INVERTEBRATES] | [INSECTS] | [VERTEBRATES]

Phylum ARTHROPODA, Class INSECTA

The dragonflies (Anisoptera) and damselflies (Zygoptera) are represented in Hawai‘i by three families, 9 genera, and about 34 species (Nishida, 1992). The largest genus is Megalagrion with 23 species and 5 subspecies, all endemic to the Hawaiian Islands (Polhemus, 1995). Many of these are threatened with extinction and members of the genus are only rarely seen on O‘ahu in lowland areas.
Selected odonate links:

[DRAGONFLIES & DAMSELFLIES]

    
Suborder Zygoptera (damselflies) Damselflies are generally smaller and weaker fliers than dragonflies, although some of our native damselflies are of pretty good size and strength (Megalagrion blackburni for example). All of the native and introduced species of damselflies in Hawai`i are in the Family COENAGRIONIDAE.

Family COENAGRIONIDAE

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  127a (125) Front wings with 5 or usually more cross-veins between node and M1/M2 junction
~ Megalagrion spp.2
  127b Front wings with 4 (rarely 5) or fewer postnodal crossveins (pn in Fig. 1) before M1/M2 junction. { Color usually a shade of blue or green; if thorax red or orange, then lacking lateral black stripes [128]

Figure 1. Wings of female Ischnura posita. Modified from picture
obtained at Damselflies of Texas.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
128a (127) Front wing with three crossveins (pn in Fig. 1) between node and M1/M2 junction. Males with small, paired projections posterodorsal on abdominal segment X (ten). Coloration blue, green, or orange. Forktails [129]
128b Front wing with 4 (rarely 5) crossveins between node and M1/M2 junction. Without knob-like projections above anus. Males a striking, deep blue on thorax and abdomen. Bluet
~ Enallagma civile (Hagen)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
129a (128) Males with an electric blue spot near tip of abdomen (Fig. 2); females green, orange, or even red, but without lateral black bands on thorax (Fig. 3). Common
~ Ischnura ramburi (Selys-Longchamps)
129b Small, rather weak appearing greenish, yellowish, or blue damselflies. Dorsal surface of thorax marked with light stripes resembling exclamation marks (Fig. 4)
~ Ischnura posita (Hagen)
I. ramburi along Kawa Stream, Kane`ohe (EBG)

Figure 2 (left).  A male Ischnura ramburi is quite distinctive with its bright blue abdominal segment between two black segments at the tip of the "tail"
Figure 3 (below).  This red-orange female I. ramburi might be mistaken for a native Megalagrion, but note there are no lateral black bands on thorax.
I. ramburi at Na Pohaku o Hauwahine, Kawai Nui marsh
I. posita at Na Pohaku o Hauwahine near Kawai Nui marsh (EBG)
Figure 4. Two views of an Ischnura posita showing the distinctive exclamation point markings on the top of the thorax.
  ~~~~~ Nymphs (aquatic) ~~~~~~~~~~~~~~~

      2 The native Hawaiian genus, Megalagrion, is a diverse group of species for which excellent identification material exists in the form of a book by Dan Polhemus & Adam Asquith, titled: Hawaiian Damselflies. A field Identification Guide. Pictures of many species are available on the Internet as listed below.

    * Native damselflies

    Figure 5.  A Megalagrion xanthomelas photographed by Rodger Douglas
    in the Moanalua area of Honolulu.

    • Megalagrion vagabundum (Perkins) / photo.
  • Hawaii Biological Survey / B. P. Bishop Museum