Male Sawfly – family argidae?
Location: Naperville, IL
June 24, 2011 6:27 pm
Hi Daniel~
I have searched and searched, and the best I can do at ID-ing this inch-long insect on my house siding is to conclude that it is some kind of male sawfly, per its wasp-like appearance and its intensely-feathered antennae. I’ve looked at conifer sawflies and argid sawflies, but the length of its body with respect to its wings is throwing me off – as is its impressive set of mandibles and armor between its wings and head. So perhaps it’s not a sawfly at all? Can you help? Thanks so much! (P.S. You asked a question a few days ago regarding two photos I sent of hatching Monarch caterpillars. The only way I was able to respond was via a comment to those photos, not in the usual way. I hope you saw my reply.)
Signature: Dori Eldridge

Male Glowworm

Dear Daniel~
I found it!  It’s not a sawfly at all.  It’s an adult male glowworm beetle – probably a Phengodes plumosa.  Those elytra and the length of its body sent me to beetles after I exhausted the sawfly and ichneumon wasp categories. There is an image on that is nearly identical to mine:  Still, you might like to add these photos to your glowworm collection.  Thanks so very much!
Dori Eldridge

Male Glowworm

Hi Dori,
We are happy that you were able to self identify your male Glowworm, and we are thrilled that we can post your photos, though we disagree with your comment that the photo on BugGuide is nearly identical to your photo.  The color and clarity of your image are even better.  It is interesting that the antennae are plumose and the species name of
Phengodes plumosa acknowledges that.  Your photos are awesome.

Male Glowworm

Yes!  …especially considering that it is only the adult male glowworms that have the plumose antennae.  I feel especially lucky to have spotted and photographed this insect now after reading that they’re not so commonly encountered.  It posed for me without moving for about 3 or 4 minutes, after which I left it.  When I returned a few minutes later, it had gone.  I hope to find a female larviform glowworm one day to photograph, too.  Thank you for your most kind words, and best regards to you.  -Dori

Location: Illinois

2 Responses to Male Glowworm

  1. Dayne says:

    What purpose do the plumose antennae of the male glowworm beetle serve? They’re intricate and large for such a sensitive body part, so I really wondered.

    • bugman says:

      Antennae are sensory organs, and while we have not read anything particular to Glowworms, we do know that male moths often have more developed antennae which enable them to sense the pheromones released by females ready to mate. We imagine the same may be true of Glowworms since the males can fly and the females cannot.

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