You may not recognize mistletoe unless it sports a red bow and is hanging over a doorway during the holiday season.

You may not recognize The Great Purple Hairstreak, Atlides halesus. Its host plant is mistletoe. (Color-cognizant folks who are fond of purple won't recognize it, either. It's not purple! It's iridescent blue!)

But what butterfly guru Art Shapiro, a UC Davis distinguished emeritus professor, wants to know is this: "Where is the mistletoe this year?"

Shapiro, who has been monitoring the butterfly populations of Central California since 1972 and maintains a research website at https://butterfly.ucdavis.edu/, is missing the mistletoe.

In a Dec. 30th email to his posse, Shapiro (who has a delightful sense of humor) wrote: 

"This was the first year in 52 that no mistletoe hung in our place at Christmas. It isn't as if we've lost interest in kissing! It's that I couldn't find any. Historically this was never a problem. Both mistletoes--the small-leaved oak and large-leafed cottonwood species--were ubiquitous, and the N winds of autumn would always bring down more than adequate amounts to meet domestic needs. Besides, the campus grounds crews would always prune a little out before the holiday break for people to collect. Just a little, not an extermination campaign!"

"When I could not find any on the ground this December I began looking up--and at once noticed there was none up in the trees, either. The corky overgrowths where it had been anchored were still there on the limbs, but no mistletoe. And this was not limited to campus! It was true throughout north and central Davis, everywhere  I habitually ambulate. Since December 20 I have located TWO heavily-infested trees in Davis on private property; that is all. It isn't as if some hypothetical disease had swept through and killed the stuff. I am used to seeing  a few dead mistletoe balls in the trees. There are none. WHAT HAPPENED? If there was an eradication effort on campus (why?), that wouldn't explain the disappearance from susceptible street trees (e.g. moraine locust) in town. I think I may have glimpsed some in far East Davis on the route of Bus 42. I need to try to track that casual observation down."

Shapiro added: "From the butterfly standpoint this certainly augurs at least the local extirpation of our most spectacular butterfly, the iridescent blue Great Purple Hairstreak, Atlides halesus, (absurdly common-named since there is no purple anywhere on it). Its larvae feed ONLY on mistletoes. Next time I am in riparian woodland, probably within ten days, I will check the status of mistletoe there, and on oaks when I am in Rancho Cordova..I will try to get to Putah Creek proper (not the Arboretum) and the North Davis Ditch, too, though I don't recall ever noticing mistletoe or the butterfly at the ditch. (There is plenty of its favorite nectar source, dogbane, so if it's there I should have noticed it.)

"Meanwhile, if you know anything about this, please let me know what you know. If you know the locations of infested trees, please tell me with the assurance that I will keep the information in confidence. FEEL FREE TO PASS THIS ALONG TO ANYONE WHO MIGHT BE INTERESTED, OR KNOW ANYTHING." (amshapiro@ucdavis.edu)

John De Benedictis, aka "The Moth Man" and a research associate at the Bohart Museum of Entomology, noted that birds spread mistletoe and wondered if the lack of mistletoe is due to fewer birds, which means less mistletoe.

"Thought of that," Shapiro responded. "In particular, there are fewer robins since the big worm die-off, and robins are big mistletoe spreaders."

Bohart associate Greg Karofelas, who has photographed many a Great Purple Hairstreak but remembers it as "The Blue Hairstreak," recalled: "When I was a kid in Woodland, we lived close to the corner of Fifth Street and Beamer Street. At that time, the big trees along Beamer were large black walnut trees (with lots of mistletoe). The faucet on the south side of our house had a small leak, so there was always mud there. Commonly, puddling on the mud was a number of what I called 'Blue Hairstreak' butterflies. I always considered it a common butterfly. I later found out that was not the case everywhere."

As an aside, we commonly see mistletoe in Vacaville on Modesto ash trees (Fraxinus velutina 'Modesto'). But not as much as we used to. 

And we don't remember seeing this butterfly species at all.  Karofelas, a skilled naturalist and talented photographer, has photographed it multiple times (see image below).

Shapiro provides detailed information on the butterfly on his website. "The common name is a misnomer insofar as there is no purple anywhere on this very showy, tropical-looking animal. The Great Purple Hairstreak occurs from sea level to about 5000' wherever its host plants, broadleaf mistletoes, occur. It is commonest in Valley and foothill riparian forest and in older urban neighborhoods with a well-developed canopy, and in foothill woodland."

He goes on to mention that the non-purple Great Purple Hairstreak visits such plants as Lantana and Zinnias and that in riparian forests, it routinely "visits Dogbane, Milkweed, Goldenrod, California Buckeye, members of the Carrot Family (Apiaceae) and the obnoxious weed Perennial Peppergrass. Pupae can be found in litter under mistletoe-infested trees, but are usually parasitized."

The hosts, Shapiro cites, are:

• Phoradendron villosum (P. flavescens var. villosum), the small-leaved mistletoe restricted to Oaks;
• P. macrophyllum (P. tomentosum), the large-leaved mistletoe found on a great variety of broadleaf trees other than oaks (and occasionally on shrubs, even Poison Oak!);
• P. juniperinum, found on junipers and cypresses (the host at Sierra Valley and on serpentine where MacNab and Sargent Cypresses occur).

The species "breeds continuously in warm weather (March-October in the Valley and foothills; June-October at Sierra Valley)," Shapiro points out. "In the Sacramento Valley it is commonest in June and September most years, but individuals can turn up any time."

So there we have it. Mistletoe is missing, the Great Purple Hairstreak is not purple--it's blue--and Professor Shapiro is on the lookout for mistletoe. And then, the very next day, "totally by chance," he spotted some mistletoe near his UC Davis  office.

Who would have thunk?