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Friday, Oct. 11, 2002


Red damselfly

* Japanese name: Beniito tonbo
* Scientific name: Ceriagrion nipponicum
* Description: The red damselfly is small (body length 34-41 mm). Damselflies can be distinguished from dragonflies (both in the insect order Odonata) by the way they perch. Damselflies rest with their wings folded together over the body, dragonflies with the wings spread out flat. The damselfly's eyes are separated on the head (dragonfly eyes meet in the middle of the head).
* Where to find them: Around water, particularly slow-flowing streams, from Honshu to Kyushu between May and October.
* Food: Other small insects. Damselflies and dragonflies have excellent vision for catching prey. They have huge compound eyes with up to 30,000 facets, giving them -- when the head is swiveled -- 360-degree vision. The larvae live underwater and spend one year growing. The larvae also eat insects, catching them with jaws that form a sort of mask on the head. When the prey is in range, the jaws spring forward, impaling the insect.
* Special features: Damselflies and dragonflies are an ancient order of insects and retain some primitive traits. They develop by growing and molting: They do not undergo complete metamorphosis, like butterflies, and their larval form looks essentially like the adult, except for the wings, which are formed during the final molt.

Damselflies have some clever tricks. The larvae breathe through gills projecting from the end of the abdomen. The two pairs of wings on adults work independently, giving them the ability to hover and fly backward. After mating (in the "copulation wheel" position characteristic of damselflies and dragonflies), the claspers of the red damselfly male are attached to the female's "neck" (between her head and thorax) and he remains in contact as she lays her eggs. This is an effective form of mate-guarding -- it ensures that he is the father of the eggs and stops another male from coming along and mating with her.

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