The Day of the Caterpillar
Rangers buttons attracts lots of insects, including bees, as seen here.
The scintillae (sparkling blue scales) are especially evident on the lower wings of this pretty female Anna’s blue.
On August 2, Sabine Dutoit, Nancy Bray, and I went up to Groundhog Mountain for a relaxing day of enjoying flowers and butterflies and whatever else we came across. We started our day in the small sloping wetland that heads downhill to the east off of Road 2309. While most of the flowers, even in the wetlands, are finishing up early this year, it was the perfect time for Cascade grass-of-Parnassus (Parnassia cirrata) and rangers buttons (Sphenosciadium capitellatum). The latter is found mainly in the southern part of the Western Cascades. It is always fun to come across. The unusual flowers have open umbels of soft, dense, spherical umbellets, the kind of thing you just have to touch. I told Nancy that this was a good host food plant for Anise swallowtails, and, sure enough, before we left the wetland, she’d found a caterpillar chewing on the leaves of a rangers buttons.
Like some other species, young anise swallowtail caterpillars bear a passing resemblance to bird droppings. They are also rather spiny. At each instar, they change their appearance a little, slowly losing the spines and the white band in the middle.
Older caterpillars become smooth and very brightly colored, with less black and more green.
Our next stop was the main wetland that fills the switchback just up the road. My one goal of the day was to look for willow thickets, something I hadn’t bothered to do here in the past. Although I had a few old photos of willow flowers from the area that didn’t look like the common Sitka willow (Salix sitchensis), I wasn’t sure exactly where I had photographed them. Happily, I found some very nice thickets on the downhill side of meadow. There were a few flowers going to seed, enough to assure me that there were two species here: Salix eastwoodiae with hairy capsules and what I believe is S. boothii with glabrous ones. While I was busy studying these, Nancy was roaming around the wetland looking for more caterpillars. I joined her after she told me she had found some more. As we walked along, she spotted more and more. What sharp eyes she has! I’ve never seen so many anise swallowtail caterpillars in one day—or ever, for that matter. We had trouble keeping track of our count. They were all on the rangers buttons, until later, at Waterdog Lake where there aren’t any rangers buttons, we found a few on lovage (Ligusticum sp.—the plants here have me confused as to species.), including the bottom right photo above. I’ve seen them in the past on Angelica and Lomatium as well, so I know they are not too picky about which carrot family members they eat, but rangers buttons seems to be their favorite when it is available [I just found some more on rangers buttons in the Calapooyas a couple of days ago—but more about that later]. We also found more at our third stop, at the little pond and wetland just north of Logger Butte. All together, we found almost 30!
With all those spines, caterpillars of hoary commas aren’t afraid to eat out in the open.
The caterpillars of cinnabar moths devouring arrowleaf groundsel
At Waterdog Lake, I walked across the meadow to where there were some sticky currant (Ribes viscosissimum) grew. After I mentioned that it was a good host food plant for hoary commas on a field trip several years ago, someone spotted them on these plants (see Group Trip to Groundhog). Funny how that happens. Well, there they were again (some of their relatives anyway!). After some searching, I turned up four. Not as welcome a discovery, there were also dozens of cinnabar moth caterpillars nearby. They were originally brought to this country as a biological control for the non-native tansy ragwort (Senecio jacobea), but now they’ve moved on to our natives. Here they were devouring arrowleaf groundsel (Senecio triangularis). Luckily, this is by no means a rare plant. Then again, its abundance can support a large and possibly growing population of these pretty but alien moths. Nancy had spotted several other caterpillars of moths or possibly skippers over the course of the day. Once you get a search image in your head, they seem to be everywhere. So, while the flowers weren’t spectacular, and even the butterflies weren’t as abundant as usual, we did have another wonderful day in the mountains.