Clytus planifrons

A couple days after I found the population of Ceanothus velutinus that I write of in that profile, I found some more plants a few miles away from there. It was sunny and warmer, and there were even more bugs than on the original patch, and by far the most exciting to me was this Clytus planifrons. I was so afraid of losing it that I didn’t even attempt to photograph it in situ, although I did have the vain hope that I’d find another one nearby feeding on the pollen. But despite a lengthy search I wasn’t rewarded with another one.

I had only found one of these rather spectacular longhorn beetles (Cerambycidae) before, and that was 4 years previously when one landed on the windshield of my parked van at a 4,000’ elevation ridge some 20 miles west of where I found this one. At that time I was rather proud of myself for ferreting out its identity, since it wasn’t in any of the books I owned (this was two years before Arthur V. Evans published his outstanding “Beetles of Western North America”) and I had to comb through hundreds of photos on BugGuide before I found a match. The color combination and patterning of this beetle put it on my ‘most wanted’ list ever since I started this website almost 3 years ago, and I was gloriously happy to finally find another one.

The aposematic (warning) patterns of many of the members of the tribe Clytini are not meant to indicate toxicity, but instead to mimic wasps, and as such is an example of Batesian mimicry (For a good overview, see Aposematism, Müllerian Mimicry, and Batesian Mimicry – Untamed Science. ). Many predators fear wasps, and with good reason, and even though the wasp mimicry of Clytus planifrons is nowhere near as good as many syrphid flies (for example Spilomyia interrupta), still it must be enough to convey a significant survival advantage, or it wouldn’t have evolved so often in the tribe Clytini. For a discussion of the efficacy of imperfect mimicry in general, see Cognitive Dimensions of Predator Responses to Imperfect Mimicry | PLOS Biology

There was a real dearth of information available online about the life history of this species, and my books weren’t much better. I assume that that is because this is not a pest species, and so there hasn’t been much research into them. And while I’d love to know more about the lives they lead, it was enough for me just to see and photograph this vivid, vibrant and wonderfully marked creature going about its life.

Description– Medium sized (9-13mm long), mostly black longhorn beetle with transverse yellow bands on the front and rear of the pronotum, and on the rear third of the elytra, as well as spots at the apex of the elytra, and three spots at the front of the elytra, and curving lines on each elytron near the middle; also has parallel yellow lines running down the face; legs and antennae mostly brown; forehead (frons) and pronotum without ridges.

Similar species– Clytus canadensis and C. pacificus lack yellow on front and back of pronotum; some Xylotrechus and Neoclytus have very similar coloring, but Xylotrechus spp. have longitudinal ridges on their frons, and Neoclytus have one or more transverse ridges on their pronotum.

Habitat– Wherever there are true firs (Abies), generally montane, at mid to high elevations.

Range– Native to the West Coast of North America; may be found region wide in the PNW in appropriate habitat.

Eats– Larval hosts are firs (genus Abies); adults feed on nectar and pollen from a wide variety of plants.

Eaten by– Presumably the larvae are parasitized by various wasps and tachinid flies, and are eaten by woodpeckers and other gleaning bird, and adults fall prey to adventurous insectivores of all orders, but I can find nothing specific for this species.

Adults active– Diurnal; BugGuide has records from May into September for this species, with the bulk of them in June/July/August.

Life cycle– I can find nothing specific for this species but eggs are probably laid on bark of dead or dying trees, and larvae probably take 1-3 years to mature; in “Beetles of Western North America” Evans indicates that adults are often found on “…fir branches on sunny ground”, which makes me wonder if they sometimes oviposit into them.

Etymology of names– Clytus seems to be from the Greek word for ‘heard of/glorious’, and may refer to the interesting patterns seen in members of this genus, but I cannot verify that. The specific epithet planifrons is from the Latin words for ‘flat/level/even’ and ‘forehead’, but I’m not sure what that refers to, since Clytus in general are known for a smooth frons.