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Insects and other arthropods

Green darners

English
Anax junius

Tabs group

Description

These large dragonflies are 6.8 to 8.4 cm long with a wingspan of more than 9 cm. The thorax is green and the abdomen is bluish to dark brown. The extremely mobile head has short antennae, well-developed mouthparts and two huge compound eyes. The face is yellowish-green with a “bull’s eye” pattern on the forehead.

The four membranous wings are wide at the base. The abdomen is slender, flexible and cylindrical.

Life cycle

The mating ritual is similar to that of other odonates. Before copulation, the male loops his abdomen forward to transfer sperm from its tip to the organ located near the thorax. He is now in the characteristic wheel position.

The male will fly up to a female and, using his genital claspers located at the tip of his abdomen, grab hold of her behind the head. To receive the sperm, the female loops her abdomen under her so that the tip of her abdomen touches the male’s organ. The pair can stay in the wheel position for several minutes.

The female lays the eggs while still attached to the male, but may also do so after the male has released his hold on her. Thousands of eggs are laid one by one on water plants, beneath the surface.

The tiny creature that emerges from the egg is called a prolarva. It must break through the plant tissue that has grown over the egg to reach the water. The first moult occurs once the larva, or nymph, is in the water.

The robust body of a green darner larva is hairless and elongated. It will go through a dozen or more moults as it develops. When it is ready for the final moult, the larva crawls out of the water and perches, head up, on an upright plant stem. During metamorphosis, the exoskeleton splits open and the adult darner emerges. The winged insect then undergoes a maturation period during which it reaches sexual maturity. Dragonflies make their way back to the water only when they are ready to mate.

Geographic distribution

The species occurs in the United States and in southern Canada.

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