{"id":63063,"date":"2022-01-10T19:42:25","date_gmt":"2022-01-10T11:42:25","guid":{"rendered":"https:\/\/besgroup.org\/?p=63063"},"modified":"2022-01-12T03:42:13","modified_gmt":"2022-01-11T19:42:13","slug":"parasitoid-wasp-2-drilling-wood-with-an-ovipositor-the-length-of-its-body","status":"publish","type":"post","link":"https:\/\/besgroup.org\/2022\/01\/10\/parasitoid-wasp-2-drilling-wood-with-an-ovipositor-the-length-of-its-body\/","title":{"rendered":"Parasitoid wasps 2: drilling wood with an ovipositor the length of its body"},"content":{"rendered":"

The parasitoid wasp Rhyssa persuasoria<\/em> (Linnaeus), also known as the giant ichneumon wasp, is used to illustrate the process of drilling wood with its ovipositor.<\/h4>\n

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Photo 1. Rhyssa persuasoria\u00a0 <\/em>Boris Hrasovec, Faculty of Forestry, Bugwood.org\u00a0\u00a0<\/a>\u00a0 licensed under a\u00a0Creative Commons Attribution-Noncommercial 3.0 License<\/a>.<\/p>\n

https:\/\/www.forestryimages.org\/browse\/detail.cfm?imgnum=9008010\u00a0\u00a0<\/a><\/p>\n

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Wasps are classified under the order Hymenoptera, suborder Apocrita. Apocrita is characterized by a narrowed waist known as a petiole, between the first and second abdominal segments. The first abdominal segment is also fused to the thorax. Hence the first abdominal segment, (after the petiole) we see in the field is actually the 2nd<\/sup> abdominal segment. Also, the larvae of all Apocrita lack legs, prolegs, or ocelli. The hindgut of the larvae also remains closed during development, with faeces being stored inside the body.\u00a0 \u00a0Apocrita include wasps, bees and ants.<\/p>\n

There are more than 150,000 species of wasps. Less than 1% of these species are eusocial. Paper wasps and hornets are examples of well-known social wasps. However, hornets can have upwards of 10,000 individuals in one nest. Thus, hornet encounters with man can sometimes lead to extremely painful or even fatal results. On the other hand, most of the wasps are solitary and seldom notice. Despite not being noticed, solitary wasps (because of their huge population numbers) are very important to Man as pollinators of plants and are one of nature’s most effective regulators of pest populations. Their larvae are parasitoid on a lot of Man\u2019s agricultural insect pests.<\/p>\n

Adults subsist on pollen and nectar and almost always hunt only to feed their larvae. With many species, individual wasps receive most of the nutrition they’ll ever get in life as larvae.<\/p>\n

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Photo 2 –\u00a0 Megarhyssa atrata (M.atrata)<\/strong><\/em> Ovipositor 3 to 4 times the length of its body<\/figcaption><\/figure>\n

Donna Fernstrom\u00a0<\/a><\/p>\n

Creative Commons<\/a>\u00a0CC0 1.0 Universal Public Domain Dedication<\/a><\/p>\n

As there are many parasitoid wasp species, there are also as many variations to the parasitoid lifestyles. We will look at Megarhyssa atrata<\/strong> <\/em>to get an idea of what a parasitoid life can be like.<\/p>\n

Megarhyssa atrata (M.atrata)<\/strong> is one of the Giant Ichneumon wasps belonging to the family Ichneumonidae, genus Megarhyssa (this genus has 32 species worldwide, 4 in North America).<\/p>\n

M.atrata<\/em> is a big wasp measuring 3.8 cm (from head to end of abdomen) for females. Males are smaller measuring about 3.5 cm. The body shape is like an extra-long cylinder. The females are mostly black in color except for a mostly yellow head, yellow feelers and legs. Part of the middle and hind legs are black. In contrast to males, the females have a long ovipositor. This is a hollow tube for egg laying, measuring 12cm to 15cm long (which is 3 to 4 times its body length). The males have more yellows on their bodies, black antennae, long segmented sausage-like abdomen and no ovipositor.<\/p>\n

M.atrata<\/em> is parasitoid on the pigeon horntail (Tremex columba<\/em><\/a>) .\u00a0 Horntails, also known as sawflies, are wood wasps which lay their eggs in wood. Many horntail species are parasitised by parasitoid wasps. Photos of\u00a0Urocercus gigas\u00a0<\/em>are used to illustrate horntail features.<\/p>\n

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Photo 3 – Urocerus gigas<\/strong><\/em> (giant wood wasp) Author<\/strong>:\u00a0Romana Pla\u010dkov\u00e1<\/a><\/figcaption><\/figure>\n

CC-BY-NC-SA-3<\/p>\n

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Photo 4 by Stanislaw Kinelski.\u00a0Urocerus gigas<\/strong><\/em> larva.<\/figcaption><\/figure>\n

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Horntails or wood wasps are wasp-like flying insects but they do not have the narrowed waist of the true wasps. They are of the order Hymenoptera and family Siricidae (which includes 150 non-social species).<\/p>\n

The name horntail is given because of the short, stout looking spike at the end of their abdomen. This horn is used to puncture the hard tree bark. Through this puncture, the female horntail then inserts her ovipositor (her second, and\u00a0 longer back end projection) and drills into the wood for about 2cm. If the wood is not too wet, she begins her ovipositing. She has hygroreceptors (microscopic sense organs called sensilla) at the tip of her ovipositor to help her. She usually deposits about 2 to 7 eggs, together with the white wood eating fungus, Cerrena unicolor, <\/em>formerly known as Daedalea unicolor<\/em>. This fungus is cultivated in a gland within her abdomen. This fungus predigest the wood and makes life easier for the horntail larvae when they hatch in 3-4 weeks. The horntail larvae grow within the dead or dying wood for 1 to 5 years. They then pupate near the bark. After about one month, they emerge as adults through\u00a0 round exit holes. Each adult horntail can lay up to 200 eggs. Horntails are found in south-eastern Canada, central and north-eastern parts of North America. M.atrata<\/em> are specific parasitoids of pigeon horntails, thus they are found in the same area.<\/p>\n

Between the months of June and September, M. atrata detects the location of a horntail larva deep within the wood of a dead or dying tree. It then drills in with its long ovipositor, maybe more than 10cm deep. It pierces the larva and injects paralysing venom. A single egg is then laid outside the horntail larva. The egg hatches and the wasp larva starts to eat up the horntail larva. The parasitoid larva pupates in spring and emerges in June to start the cycle.<\/p>\n