Rove Beetle

 

It was a dreary rainy day with little hope of finding things of interest until Barb was cleaning a batch of winter oyster mushrooms and out raced a rove beetle.  "Quick bring a bug box!" she cried and soon it was ready for photography and its few minutes of fame.

A quick trip to INaturalist identified it as Philonthus caeruleipennis (PC).  I couldn't find any details on the web but it had an entry in Evans' Beetles of North America.  Adults are active in the summer and are "associated with fungi, compost and decaying vegetation."

 

PC is a member of the Staphylinidae family, aka rove beetles.  Their distinguishing feature is their short elytra (wing covers) that typically leave more than half of their abdominal segments exposed.  In this case PC has iridescent blue-green elytra covering less than a third of the abdomen.

We were fortunate that PC was so distinctive.  Rove beetles are the largest beetle family with 63,000 species in thousands of genera.  Most rove beetles are predators of insects and other invertebrates that live in decaying plants and leaves.  They have a wide variety of other lifestyles including living in ant colonies, as parasitoids, and even a few that cling to animals to eat fleas and parasites.

The winter oyster mushroom, Pleurotus ostreatus, is a cool find also.  It is firmer than the summer P. pulmonarius and its gills run down the stalk all the way to the base.  While getting its nutrition from dead or dying trees, it likes the occasional protein of nematodes which it attracts and digests with its hyphae.  The gory details are in this blog.

Pleasing fungus beetle, Triplax thoracica

Our PC rove beetle lives on the little fungus beetles that are found in the gills of all our oyster mushrooms.  They range from 3-5 mm and we find them in the gills of every batch, even though the host trees may be a quarter mile apart.  Pleasing fungus beetles specialize on oyster mushrooms.  How they find this ephemeral food source when it briefly emerges and how they survive without eating for so long remains a mystery.

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The next night Barb fixed an oyster stew with the remaining oyster mushrooms. Just before sitting down to eat she glanced at the empty mushroom container and found these critters crawling around, having escaped the mushrooms and the frying pan.

The mushrooms had been cleaned initially and inspected again before cooking. The obvious question is how many of these do we miss and consume.  I think of it as a health food, just a matter of marketing like the "cholesterol free" sticker on a banana.  Look at the positive side.

Protein enhanced
Vitamin enriched
Gluten free
No preservatives
All natural ingredients

Bon appetite!