When I found the first of these on my recent trip to Mt. Hood I was very excited, because I’m always excited to find bugs with interesting patterns, and because I knew I’d seen a similar elytral pattern before in one of my books. It was pretty cooperative and let me get some decent photos as it buried its nose in a lupine flower, and I was able to collect it after getting its portrait. And a bit later I found a similar, but slightly differently patterned, beetle that I photographed and collected. One of the first things I did when I got back to the car was to open “Pacific Northwest Insects” to the longhorn beetle pages, and I quickly found the photo of Evodinus vancouveri. But that didn’t look quite right because the pronotum didn’t flare toward the base, as well as being a little off for the pattern. It seemed likely they were Judolia though, which were listed under similar species, but I had lots of things to identify and didn’t get back to it.
Then the following week I was back at Mt. Hood looking for Euphilotes sp. butterflies, and generally exploring, and I saw what I at first thought was a hymenopteran hovering around a lupine, and when it landed I realized it was another of what I presumed to be Judolia beetles. Then I got distracted by a Drasteria moth zooming by, and when I returned my attention it was gone. Shortly thereafter I noticed that odd flight pattern again. In my, admittedly limited, experience beetles are either poor fliers who kind of drift in a general direction, or they zoom from point to point. Because I was paying better attention to this one I immediately noticed the bottom heavy flight that is indicative to me of a beetle, but this was very controlled, and it was obviously checking out the flowers in flight, rather than just landing and then walking to the best ones.
When it did land I thought that it looked like a negative image of the Judolia, since it was mostly black with some tan marks, as opposed to being mostly tan (the books call it yellow, but it looks tan to me, and Pam thinks it’s a kind of green), with black marks. Thinking it was a different species I netted and secured it without giving it a chance to escape. But I was attuned to that odd flight by then, and I saw a few more, and even managed to get some photos. I was pretty excited by these little bugs, and in spare moments over the next couple days I tried to figure out what they were.
This is where it gets a little embarrassing, because, despite the similarities in flight and body shape between the black with tan marks beetles and the tan with black marks Judolia, and despite the variation I’d already seen, I didn’t actually check out Judolia for different color phases. I didn’t even read the section on Judolia in Phil Schapker’s “Lepturine Longhorn Beetles of the Pacific Northwest”, although I paged past it several times looking at photos, and so missed him saying that Judolia instabilis is “…one of the most variable lepturines in North America.” I became rather frustrated with my inability to get a handle on those beetles and thus, in the course of corresponding with Merrill Peterson about the shipping of butterflies, I asked him if he knew what they were. And, as you’ve probably guessed, he told me they were probably a color morph of Judolia instabilis. Which I then confirmed by keying out all three of the beetles using Schapker’s treatment, which is what I should have done before asking someone else to do the work for me.
Description– Small to medium sized (6-15mm) longhorn beetle with a dark head and pronotum that look lighter because of greyish tan setae, and elytral markings that vary from mostly yellow with black spots to mostly black with some yellow spots; markings tend to be rounded or smooth, and the scutellum is flush with the elytra; pronotal margins grooved on all sides; elytra apices are rounded to pointed; pronotum flares outward where it meets the elytra.
Similar species– Judolia montivagans has the scutellum recessed below the elytra, the apices of the elytra are truncated, and the transverse black blotches tend to be more irregular than rounded or flat; J. gaurotoides lacks a depression at rear of pronotum, and the transverse black blotches tend to be more irregular than rounded or flat; Evodinus vancouveri pronotum does not flare substantially at the rear.
Habitat– From the limited information I can find this species seems most prevalent in montane areas with pines and lupines.
Range– Western North America; possibly region wide in the PNW in appropriate habitat.
Eats– “In California and Oregon, J. instabilis is most frequently observed on lupines, which has led to some speculation that lupine might be a host plant. Pinus is known to be the host for J. instabilis in the southern extent of its range in Arizona and Mexico, as well as in British Columbia.” https://osac.oregonstate.edu/sites/default/files/Lepturines%20of%20the%20PNW-7%20in-v.1.1.pdf; In “Beetles of Western North America” Arthur Evans states “Larvae in roots of vetch (Astragalus) and lupine (Lupinus). Diurnal adults frequently on flowers, especially lupine (Lupinus) and buckwheat (Eriogonum)…”
Eaten by– Larvae are presumably host to wasp and fly parasitoids, and adults and larvae are probably preyed upon by insectivores of all classes, but I can find nothing specific for this species.
Adults active– Diurnal; May into September.
Life cycle– I can find nothing specific to this species, but eggs are probably laid on or near the host, and larvae probably take 1-3 years to develop into adults.
Etymology of names– I can find no Latin or Greek words that seem to correspond to Judolia, and possibly Mulsant named this genus after a person, but he does not deign to tell us to what he is referring. The specific epithet instabilis is from the Latin word for ‘changeable/unsteady’, and possibly refers to the enormous variation in the elytral markings of this species, but if Haldeman explained this I cannot find it.