Ichneumon wasp

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Ichneumon Wasp
Megarhyssa macrurus Female
Megarhyssa macrurus Female
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Suborder: Apocrita
Superfamily: Ichneumonoidea
Families

Braconidae
Ichneumonidae

The Ichneumon wasps are insects classified in the Parasitica group of the suborder Apocrita within the Order Hymenoptera. Often inaccurately called ichneumon flies, they are solitary insects, and most are parasitoids—the larvae feeding on or in another insect which finally dies. As with all hymenopterans, ichneumons are closely related to ants and bees.

The superfamily Ichneumonoidea (consisting of two families: the Ichneumonidae and the Braconidae) has been estimated to contain well over 80,000 different species. Some members use many different insects as a host, others are very specific in host choice. Various ichneumons are used successfully as biological control agents in controlling pests such as flies or beetles.

Female Megarhyssa laying eggs
Female Megarhyssa laying eggs

Ichneumon species are highly diverse - ranging from 3mm (1/8-inch) to 13 cm (5 inches) long. Most are slender, with the females of many species (particularly in the genus Megarhyssa) having an extremely long ovipositor for laying eggs. The female finds a host and lays an egg on, near, or inside the host's body. Upon hatching, the larval ichneumon feeds either externally or internally, killing the host when they themselves are ready to pupate. Despite looking formidable, the ovipositor does not deliver a sting like many wasps or bees. It can be used by the wasps to bore into and lay eggs inside rotten wood.

Charles Darwin found the grisly life cycles of Ichneumons incompatible with the central notion of natural theology which saw the study of nature as a way to demonstrate God's benevolence. In a letter to American botanist Asa Gray, Darwin wrote "I cannot persuade myself that a beneficent and omnipotent God would have designedly created the Ichneumonidae with the express intention of their feeding within the living bodies of Caterpillars, or that a cat should play with mice."

Members of the family Ichneumonidae are usually larger than members of the Braconidae, and are distinguished primarily by details of wing venation. They are also sometimes called "Scorpion Wasps" due to the extreme lengthening and curving of the abdomen. This lengthened section may also be segmented. Many species in both families utilize polydnaviruses to suppress the immune system of the host insect.

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