What is this beetle and what are the strange antennae for? I found this wonderful creature in my yard (I live in the south of France) last night: !enter image description here !enter image description here It was about 2-3cm long, with a hard carapace and wings. It also made loud hissing noises when agitated. I am curious as to what species this is, I'm quite surprised I'd never seen it before cause the beastie is quite large and last night I found it because of the _noise_ it was making. It was upside down and hissing like a kettle. More than the specific species' name, I am curious as to what the large antennae are for. Does their shape and size somehow increase the beetle's sensitivity to whatever stimuli these are atuned to? * * * Alan Boyd's comment below helped me along a bit. I seem to have found a close relative of the ten-lined June beetle (Polyphylla decemlineata) pictured below (image source) !enter image description here

From the pattern on the elytra (hard upper wings), it looks like you might have a beautiful male _Polyphylla fullo_. Compare your photos with the _P. fullo_ in this illustration, or photos on the Wikipedia page.

**edit to fully respond to the comments:**

I suspect you're right that the antennae plates in your picture are just tightly closed up, giving a different appearance. Here's a photo I took of a related species where you can see both appearances of the antennae.

And I think that Alan Boyd is correct about the antennae being used as chemoreceptors to locate females. The wikipedia page on the Ten-Lined June Bug also mentions both of these points.

!enter image description here