Don’t mess with soft-winged flower beetles

Melyrid beetle at Point Reyes N.S., CA

Melyrid beetle at Point Reyes N.S., CA

Another little tale from my enigma bucket. For a number of years I have been casually trying to work out the chemicals produced by some of the local melyrid beetles. Many species have eversible abdominal and/or thoracic pouches, vivid aposomatic colors and some tropical species are apparently are the source (or a source) of defensive compounds for birds and frogs. I can easily show that they are distasteful by offering a predator like a crab spider an unprotected prey item like the cricket in this video Spider eats cricket, which the spider  grabs and eats and then compare that to what happens when a melyrid is grabbed by a crab spider spider and melyrid. The crab spider clearly rejects the beetle and the beetle walks away unharmed. The beetle and crab spider in the video were collected together on flowers of a native Prunis in southern California and so this sort of encounter must happen regularly in nature.

Even stranger, when the flightless, intertidal melyrid, Endeodes was offered to a jumping spider that lives in the same habitat with it, the spider grabbed the beetle, carried it around for several minute without biting it and then released it. The beetle was a little roughed up, but not obviously harmed. What is that about?!

As for the chemicals that I presume must be on the eversible sacs, initial analyses didn’t show anything remarkable (looked at by me and also by the late Thomas Eisner). Various assays, including rinses and extracts of the beetles applied to crickets, had no deterrent effect. I haven’t done the deep dive on this and everything is very preliminary, So like the mystery of the bursal glands in my last post, this remains an puzzle for another day or another person for figure out.


About Kip Will

I'm an insect systematist with expertise in carabid beetles, who is always happiest in the bush.
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One Response to Don’t mess with soft-winged flower beetles

  1. Alan Kaplan says:

    Hey, Kip!
    Alan Kaplan here.
    I had a Collops versitalis (male) in my yard today. I’ve seen females earlier in the spring; I sure hope he can find a mate. Has anyone looked at the chemicals in the strange 2nd segment of the male antenna? Supposedly females feed from them. There are European malachiines (malachiidiniae) (whatever) that have mating behaviors around some kind of feeding of females on male secretions, but the paper was in German, and it was a long time ago….
    I stumbled upon this (your blog) when looking at Chorosine that Pitohui birds in New Guinea get their poisons from.
    Best regards always!

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