Forest Co-habitating Microfauna

Yesterday, my husband took me for a walk in the woods near our home and while I always enjoy the fresh air and the quiet beauty of the woods, I especially appreciate the opportunity to discover new bugs. I was really hoping to come across one beetle in particular, a ground beetle that I’ve only seen three times since September 2009, when I first moved to San Juan Island.

It’s called Matthews’ Angry Gnashing Beetle or Zacotus matthewsii. Zacotus means “very angry” in Greek, though I’m not sure why this beetle would ever act in an angry manner unless you were poking it with a stick. In that case, it’s likely it would attempt to defend itself by gnashing at you with its mandibles, and any bites you receive would be well deserved indeed!

The last sighting I had of a live Zacotus matthewsii was February 18, 2015 at 5:56 p.m. I’m hoping to walk along the same spot again this evening about the same time in hopes of sighting another.

These ground beetles are extremely unique. Their maroon-red metallic coloring is often ringed with a green shimmer along the margins of its body.

Zacotus matthewsii 2/18/15 Three Corner Lake Road San Juan Island, WA

Sadly, the life history of these beetles is understudied. We do know they are only associated with old growth forest ecosystems and rarely seen. When old-growth forests are cut down, the beetles disappear and our opportunity to know them is lost.

While I didn’t find one of these beetles yesterday on our walk in the forest, I did come across some equally interesting residents, cohabitating in a rotten log near a stream. I might have missed them entirely, but for my curiosity leading me to lift off a section of the log. It was a bit like lifting the roof off a house, and being able to see all the rooms and inhabitants, only instead of being a multi-family unit, this was a multi-species, multi-family unit!

I’d packed my cellphone and my handy clip on macro lens, so I was able to take some video and photos to share with you. Here’s what I found!

The first amazing creature that was exposed in the log was a centipede. This is Scolopocryptops spinicaudus. I noticed nearby, there was a grouping of eggs, so after a bit of internet searching, I discovered the very neat fact that these (and other species) of centipedes stay with their eggs.

The mother will wrap herself around the cluster to better protect them, staying with her brood even weeks after they hatch, leaving them only after they are able to fend for themselves. I believe this mother centipede moved away from her eggs when I removed the section from the log in order to draw my attention away from them.

***Eggs were not disturbed and I replaced the log section after taking my photos.

Scolopocryptops spinicaudus Centipede with eggs
Scolopocryptops spinicaudus with eggs
Lester Parcel
Scolopocryptops spinicaudus (Centipede) eggs 2/16/2020 Lester Parcel

Below is a photo I found when I was searching about centipedes and parental care. I find it amazing that even invertebrates show such care for their offspring!

Centipede caring for eggs

The next resident in the log that caught my eye was the very tiny, whitish-translucent, globular creature that looked a lot like a bark or booklouse, but turned out to be a “baby” termite. These were larvae of the Pacific Dampwood Termite, Zootermopsis angusticollis. I wasn’t able to get a good view, but it looked as if these were being tended by an older family member.

Dampwood termites are widespread in Pacific Northwest forests. They rarely cause damage to structures, but play a very important ecological role, recycling nutrients from decaying trees. They are also food for Pileated Woodpeckers and other birds and animals.

Pacific Dampwood Termite (Zootermopsis angusticollis) larvae
2/16/2020 Three Corner Lake Road, San Juan Island, WA
Zootermopsis angusticollis larvae

Finally, the last residents I spied cohabitating in this section of rotting log were the very tiny Wrinkled Bark Beetles (Clinidium spp.) Clinidium spp. of bark beetles feed on slime molds (Myxomycetes), found in decaying or dead hardwoods and conifers. They are in the Family Rhysodidae and there are only two genera and eight species in North America. Only two of these eight species range in the West (from California to B.C. ) (White, 1983).

At about 5mm in length, these were hard to detect with the naked eye. I took the following photos with my macro lens, showing the striations along the elytra and the lateral grooves on the basal half of the pronoun.

Wrinkled Bark Beetle (Clinidium spp) 2/16/2020

The next photo shows two adults together, presumably hibernating together in a cavity in the rotting log (White, 1983) .

Wrinkled Bark Beetle adults hibernating together (Clinidium spp) 2/16/2020


Lattin, John, D. 1993. Arthropod Diversity and Conservation in Old-Growth Northwest Forests. American Zoologist. 33 (6) pp. 578-587.

White, Richard. 1983. A Field Guide to the Beetles of North America. Peterson Field Guide Series. Houghton Mifflin Company, NY.

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