Ischnura gemina (Kennedy, 1917)

Ischnura gemina

Species recognized by J van Tol, Catalogue of the Odonata of the World external link in 
L’état de conservation d’UICN: Vulnerable (VU) external link Switch to common names

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Morphology

Physical Description

Source et information additionnelle
Author
Jana Marshall
Copyright
©1995-2008, The Regents of the University of Michigan and its licensors Some rights reserved external link
Supplier
Animal Diversity Web external link
Editor
Stephanie Fabritius
Source URL
View original data object external link
Citation
Marshall, J. 2001. "Ischnura gemina" (On-line), Animal Diversity Web. Accessed September 28, 2008 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Ischnura_gemina.html.

Ischnura gemina are known for their large compound eyes each separated by more than their own body width, muscular mandibles, very slender, elongate ten-segmented abdomens, short legs used mostly for perching, and tiny filiform antennae. Sight is their most specialized sense. Unlike the dragonfly, their two pairs of large wings stand straight up over their 7-8 cm long bodies. The female adult has a black humeral stripe, lacking the pale spot located at the base of the median ocellus that the males exhibit. Females also have specialized ovipositors whose primary function is to cut holes in the stems of submerged plants in order to receive eggs. Adults are called "darning needles" or "mosquito hawks" due to their size, which decreases with advancing season.

Each adult female usually has 11 to 14 nymphs, whose life cycles take up to one year. The eggs and larvae have caudal and rectal gills. Ischnura gemina nymphs are identified by their three leaflike tracheal gills at the tip of their abdomen and their usually robust green or grey color. Nymphs are usually 10-15 mm long, not including their gills. The bodies of the nymphs bear small spines and are often covered with algae and debris. They have five labial setae or food getting devices armed with stout teeth. (Brackenbury, 1994; Brusca and Brusca, 1990; Corbet, 1999; Merritt and Cummins, 1984; Pennak, 1953)