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The Vapourer Moth—Wingless Females and Hairy Caterpillars

Updated on August 17, 2017
marlies vaz nunes profile image

Marlies obtained her PhD in entomology at the University of Amsterdam, the Netherlands. She likes writing about insects and other subjects.

A caterpillar of Orgyia antiqua
A caterpillar of Orgyia antiqua | Source

The hairy caterpillars of the vapourer moth, Orgyia antiqua (Order: Lepidoptera; Family: Lymantriidae) are the prettiest that we've ever seen. They are also known as the rusty tussock moth. They are gray with red and yellow spots and carry four chimney-like tufts of cream-coloured hairs on their backs as well as two horn-like bundles of hair on their head and one at the rear end.

They live on many plants, such as rose, buddleia, rhododendron, hawthorn, apple. One should not pick them up or touch them with bare hands, as the hairs can cause irritation of the skin.

The female moths are wingless and look like brownish-grey sacks, whereas the males are fully winged and are orange-brown with a white spot on each forewing.

The Males of the Vapourer Moth are Fully Winged and are Orange-Brown With a White Spot on Each Fore Wing ...
The Males of the Vapourer Moth are Fully Winged and are Orange-Brown With a White Spot on Each Fore Wing ... | Source
... Whereas the Female Moths are Wingless and Look Like Brownish-Grey Sacks.
... Whereas the Female Moths are Wingless and Look Like Brownish-Grey Sacks. | Source
Eggs of the vapourer moth
Eggs of the vapourer moth | Source

Biology of the Vapourer Moth

Caterpillars emerge from May onwards and feed until August-September. Female caterpillars feed some 10 days longer than males. Consequently, female caterpillars become much longer and can reach a length of up to 25 mm, compared to 15 mm for male caterpillars. Female and male pupae are, therefore, also different in size.

This is one of the few cases where sex can be established before the pupal stage.

The mature caterpillars spin a loose cocoon, often between leaves or on a twig, in which they process their body hairs. Inside the cocoon they pupate.

A few weeks later the adult moths appear, the males usually emerging earlier than the females.

The female stays near or on top of her cocoon and 'calls' males by emitting a volatile substance. After mating, the females produce 200-300 eggs on top of the cocoon. The females do not move away and probably die soon afterwards. The males die in autumn or winter, but the eggs - that have very hard shells - overwinter.

A Walking Caterpillar

Males are Extremely Good at Finding Females, as We Found Out.

One afternoon in August three vapourer moth males entered our flat through an open bedroom window, within one hour’s time. We captured the first two and released them, surprised why suddenly two identical moths had come inside, as we had never seen any of them in the neighbourhood, before. The third had made it all the way to the kitchen, and then we understood: the caterpillar that we had kept in a cage in the kitchen, and that had pupated a few weeks earlier, had just changed into a female vapourer moth - she must have been calling the males!

Damage by Orgyia antiqua

As mature caterpillars can eat quite a large amount of leaf, they can be troublesome in gardens. However, they seldom appear in large enough numbers to become a pest and if an outbreak is severe, it is always local.

Atanycolus sp., a braconid wasp
Atanycolus sp., a braconid wasp | Source

Natural Enemies of the Vapourer Moth

The moths will undoubtedly be eaten by birds, spiders, and wasps of the Vespidae family. The latter are even known to 'steal' moths from spiders' webs.

Hairy caterpillars like those of O. antiqua, are usually avoided by birds, except for one bird that is specialised in hairy caterpillars: the cuckoo.

Other predators of caterpillars (hairy or not) are ground beetles (Order Coleoptera; Family: Carabidae), in particular, Calosoma sycophanta.

The caterpillars are also attacked by parasitoids, such as the wasps of the family Braconidae (Order: Hymenoptera) and tachinid flies (Order Diptera; Family: Tachinidae), whose larvae develop inside the caterpillar's body.

Treatment of the Vapourer Moth (Usually Unnecessary)

  1. If treatment is required, then remove the cocoons and eggs in winter. Wear cloves to avoid contact with the urticating hairs in the cocoons, as they can cause irritation of the skin!
  2. One could also try to attract tachinid flies and braconid wasps, by growing flat-topped open flowers, such as Compositae (e.g. daisies) or Umbelliphorae (e.g. dill).

© 2012 Marlies Vaz Nunes

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    • profile image

      Tarne Cogman 3 days ago

      Brilliant and insightful post into this marvoulous critter. We've had a few around our garden recently but as other readers suggest they are too beautiful to remove. Many thanks.

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      Lyn Cottrell 6 days ago

      Your article was really helpful to me this morning as I tried to identify the very beautiful caterpiller I found on my wisteria. I don't think I can upload photos to this post but if I could I would put one on. I have replaced him on the plant as he seems to be the only one and is too gorgeous to harm.

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      Kris 9 days ago

      Very interesting information about caterpillars, thankyou

    • Lady Lorelei profile image

      Lorelei Cohen 4 years ago from Canada

      I love you buggy articles. You have so much information to share with those plagued by the nasty little pests that haunt our gardens in summer and on occasion our home. I don't think that I have ever seen a Vapourer moth or I do not remember that I have.

    • kindoak profile image

      kindoak 5 years ago

      I like insects, and most of them do more good than damage! Interesting facts about this moth type.

    • Steph Tietjen profile image

      Stephanie Tietjen 5 years ago from Albuquerque, New Mexico

      This is a fascinating creature. I never knew a moth could be wingless. Thanks for another interesting read.

    • LiteraryMind profile image

      Ellen Gregory 5 years ago from Connecticut, USA

      As always an interesting lens about insects. Keep the insect lenses coming -- they are fascinating.