Tuesday, 21 April 2020

What Comes Out of the Firewood


I was recently in a Facebook discussion with someone living near Stockholm about some beetles that she had appear in the house. They were longhorns so we are fairly sure they have emerged out of her firewood which has been brought into the house. This happens to us here in the Loire Valley too, so I thought I'd write a blog post about the species we've met as a result of having a wood stove.

Lesser Capricorn Cerambyx scopoli (Fr. Petite capricorne)
A very rugged black beetle with a textured look. Ponderous and immensely strong they are not too fussy about their host tree. The larvae will bury themselves in the living heartwood of mature broadleaf deciduous trees that are a bit isolated and get a lot of sun. If you frighten them the adults will squeak at you in protest.

Lesser Capricorn beetle Cerambyx scopoli.  Indre et Loire, France. Photographed by Susan Walter. Tour the Loire Valley with a classic car and a private guide.


Welsh Oak Longhorn Beetle Pyrrhidium sanguineum (Fr. Callidie sanguine)
This is the most common firewood emergeant, the smallest, but the most visible. The red colouration is not created by the pigmentation in the wing cases, but is more like a red gold dusting of scales and hairs that can be rubbed off to reveal a glossy black beetle beneath.

Welsh Oak Longhorn Beetle Pyrrhidium sanguineum.  Indre et Loire, France. Photographed by Susan Walter. Tour the Loire Valley with a classic car and a private guide.


Plagionotus arcuatus (Fr. Clyte arqué)
Such a good wasp mimic it's easy to be fooled, but it is actually a type of longhorn beetle, readily identifiable by the bow shaped yellow markings. The beetles can be anything from 8 to 20 mm in length. It is lustrous black with bright yellow spots and stripes. The legs and antennae are orangey brown. They like to hang out in the sunshine on dead oak and beech. Their colouring makes them look like wasps, but to add to the effect in life they move like Vespula spp wasps. A charming and pretty beetle.

Plagionotus arcuatus, a longhorn beetle.  Indre et Loire, France. Photographed by Susan Walter. Tour the Loire Valley with a classic car and a private guide.


 Spotted Longicorn Chlorophorus glabromaculatus (Fr. Clyte poilu)
 A black beetle that is covered in golden down, except for a series of spots on the wing cases and thorax. Adults eat pollen and can be found in gardens. The larvae like dry dead wood, especially oak, but sometimes other deciduous trees.

Spotted Longhorn Chlorophorus glabromaculatus.  Indre et Loire, France. Photographed by Susan Walter. Tour the Loire Valley with a classic car and a private guide.


Sometimes the beetle doesn't get a chance to emerge. The last photo shows a larva of a longhorn beetle Cerambycidae in our oak firewood. I'm told it is likely to be Leptura sp or Clytus sp, or a closely related genus. Based on that and the size of the larva, I think it could be either Plagionotus arcuatus (Fr. Clyte arqué) or Spotted Longicorn Chlorophorus glabromaculatus (Fr. Clyte poilu).

Longhorn beetle larva.  Indre et Loire, France. Photographed by Susan Walter. Tour the Loire Valley with a classic car and a private guide.

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4 comments:

Colin and Elizabeth said...

Great memory. It took us a while to realise they came out of the wood. It could well of been you that told us!!! We now get very small black flies from the house plant compost.

Le Pré de la Forge said...

Nice post....

Susan said...

Sciaridae Dark-winged Fungus Gnats are the most likely small black flies emerging from potting mix.

Susan said...

Thank you.

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