Another Butterfly Day at Spring Prairie

There’s quite a contrast between the Boisduval’s blue caterpillars almost motionlessly eating lupine pods and the frenetic activity of the ants running up and down stems and back and forth across the caterpillars. Most of the caterpillars we found were tended by these large red-and-black ants.

After the wonderful trip to the rock garden on the way to Spring Prairie in July (see Beautiful Spots on the Road to Spring Prairie), I was anxious to return to the area and check out the other spot I hadn’t been to in many years. Spring Meadow is a wetland in the drainage of Mule Creek between the rock garden and Spring Prairie. On August 3rd, Sheila Klest and I headed up Road 733. We saw lots of butterflies along the road, including quite a few at a patch of spreading dogbane (Apocynum androsaemifolium) I hadn’t known about. I definitely wanted to check it out but decided we should drive all the way to Spring Prairie first and work our way back slowly.

A few of the caterpillars had smaller ants. Although the caterpillars ranged from green to this paler pinkish color, they all had a reddish purple stripe down their back.

I was delighted by this sign someone left on a rock near the Spring Prairie shelter pointing to the clump of coralroots growing in the beargrass on the right. While they were western coralroot (Corallorhiza mertensiana) and not striped coralroot (C. striata) as indicated, I appreciated the thought.

Changeable phacelia is a rather unassuming plant, often found on roadsides. Its off-white flowers might not inspire one to plant it in the garden, but it is a favorite nectar plant for bumble bees and butterflies. I can see 15 Anna’s blues in this photo, but there were even more on nearby plants.

Just like the trip to Spring Prairie last year (see Exciting Day at Spring Prairie), it only took a few minutes to find evidence of butterflies reproducing here. On July 25, 2021, I found lots of Anna’s blues (Plebejus anna) laying eggs. This year, we found many caterpillars probably in their final instar. Adult Anna’s blues were already flying, only have one brood a year, and overwinter as eggs, so I think what we saw are Boisduval’s blues (Plebejus icarioides). As I discovered last year in nearby Beall Prairie, the key to finding the cryptic slug-like caterpillars was to look for ants. It is not known whether Anna’s blues are ant-tended in the Cascades, so that’s another reason to believe these are Boisduval’s, which are known to be ant-tended in our area. Both use lupines as their host plant.

Sheila and I scoured the lupines (Lupinus sp.) growing among the beargrass (Xerophyllum tenax), finding caterpillars almost everywhere we looked. I can’t recall now how many (It would have helped if I’d had time to write this back in August!), but we saw well over a dozen before deciding it was time to move to our next spot. We walked to the bend in the road just past where the trail to Blair Lake intersects. There is a little flowery patch with several especially good pollinator plants. In addition to lots of Anna’s blues, we saw a pair of pale swallowtails, an anise swallowtail, and several fritillaries. The blues were enthralled with changeable phacelia (Phacelia mutabilis), while the swallowtails enjoyed mountain thistle (Cirsium remotifolium). The large patch of Parry’s arnica (Arnica parryi) I’d seen last year was also in bloom but not attracting much attention.

As we left Spring Prairie at about noon, there was a bit of light smoke to the east, but it was otherwise a clear and beautiful day. Very little of the beargrass bloomed there this year.

We left Spring Prairie and drove back down the road about a mile until we spotted a shady spot to park near what looked like a trail down to the lower of the two small lakes. Sure enough, there’s a well-trodden trail to the lake. From there, we had a more difficult bushwhack farther downhill through a stretch of forest into a sloping wet meadow. Here we had to watch our step because there were hidden rivulets of water coming down, and the vegetation in August was so tall we couldn’t see the ground. But walking slowly and carefully is fine while looking for plants and butterflies, so we didn’t mind.

Shrubs line the small track of Mule Creek through Spring Meadow, and the fluffy white inflorescences of cottongrass dot the wetland.

Anna’s blues blithely tootling about on the moss near some sundews.

Down at the bottom of the slope, the vegetation was much shorter, and it was much wetter. We found round-leaved sundews (Drosera rotundifolia) and cottongrass (Eriophorum gracile), good indicators of a bog. Anna’s blues were abundant here as well, although we didn’t see any lupines or signs of caterpillars. The poor blues, however, didn’t seem to realize how treacherous this area was to them. Dozens of them puddled on the ground inches away from rosettes of the carnivorous plants’ sticky leaves. Every time we inadvertently disturbed some butterflies, they flew up in the air for a few minutes, making me nervous they would land too close to the deadly sundews. I can only imagine it was for the moisture that this area was so popular because although we saw a few nectaring on flowers here and there, most of the blues were down on the ground.

This is what happens when the butterflies get too close. The sticky hairs on the sundew leaves trap the butterfly, eventually providing the nourishment the plants have trouble getting in the nutrient-poor conditions of the bog.

After surveying most of the area to add to my plant list for the areas near Road 733, we headed back up to the road. Looking back toward the east, we were taken aback by the sight of smoke coming from what appeared to be just over the hill. Our relaxed mood quickly turned apprehensive. Where did this come from? Could some unknown fire that had barely started days before have suddenly heated up? We got back to the car and continued down the road. I had really wanted to show Sheila the sweet upper lake and its wetland, but we just got out of the car for a couple of minutes so I could point it out. Neither of us could have enjoyed a walk to the wetland not knowing what was going on with the smoke. We continued down the road, sadly passing the dogbane patch I had wanted to look at. All I wanted to do at that point was to hightail it out of there.

Not the sight you want to see when you are in the mountains over 10 miles of gravel road away from “civilization.”

Shortly after, we passed by an open area along the road where we could get a long view to the east and see where the smoke was emanating from. There was an impressive plume billowing up from about 10 miles to the southeast and blowing in our direction. We hadn’t yet heard of the Cedar Creek fire, so we were confused as to which fire it was. We found out later that this fire had started near Waldo Lake just two days before. We also had no idea how destructive this fire would become, almost reaching the town of Oakridge during some extreme heat and wind in mid-September and eventually burning over 120,000 acres. We were incredibly relieved at the time to find the fire wasn’t anywhere near our location, but tragically, when the fire blew up, it burned westward through the entire area from Waldo almost to Oakridge, right past Spring Prairie and Blair Lake. What became of all our butterflies, I don’t know, but I imagine the area will never look the same—certainly not in my lifetime. I had hoped to get back up to Spring Prairie later in August, but by then, the smoke was so bad, there was no going near the area. And we probably won’t be able to go into the area next year at all because of the danger of falling trees. I do hope that somehow at least some of this special spot was spared the worst of the destruction. And hopefully the wetlands and rock garden will not have burned too badly. Though it will most likely be terribly depressing, I do want to return to see how things recover. Plants can remarkably resilient.

Although we were relieved to see how far away the fire was from us, high temperatures and strong east winds in September allowed the Cedar Creek Fire to grow from 33,000 acres on September 9 to 85,000 acres just two days later, and it eventually burned right across this area and 6 or 7 miles even farther west. On this day—August 3, it was only reported as 500 acres but was already moving well and more than doubled by the next day.

After discovering that we weren’t in any danger, after all, we decided to head over to nearby Blair Lake to collect some seeds and do a bit more botanizing. From the wet meadow at the trailhead, we could see a hint of the smoke above the ridge, looking more like a bit of cloud, but from the lake and campground, the ridge blocked all signs of it. It made me wonder if the fire had in fact been nearby, would anyone have realized it? Thankfully, we had the foresight to bring bathing suits in case we wanted to go for a swim. After our scare, going for a very relaxing swim in the lovely lake was just what we needed to end our outing.

4 Responses to “Another Butterfly Day at Spring Prairie”

  • Ingrid Ford:

    Wonderful post with great photo of ants on caterpillar. You seeing the start of the Cedar Creek fire which burned all summer long which is devastating but the sign of our times. I want to revisit Waldo lake after I watched salmon spawn right below/beside my kayak the year before the fire. Thank you Tanya for sharing your trips with us.

  • Leigh Blake:

    OMG!!!! WOW…so glad you are safe!!! Gorgeous photos…Love the caterpillars… Is the same one that lays eggs on the Lupine ( Lupinus bicolor) ?? My knowledge is scant here…but I love these butterflies…

    The Cedar Creek fire was a frightening event…along with the other fires that burned this summer… I am so grateful that you were nor nearer… Too near to be sure!!!

    Thank you… Love the ants tending this caterpillar…

    THANK YOU!!!

  • Kate Shapiro:

    Tanya, hi & seasons greetings. I’ll add a big “thank you” for the great field trip reports. Each is a fair amount of work in the field & on the computer. About the ants: I am not a myrmecologist, but have an interest in ants. I’d guess the ants in your photos are Formica obscuripes, Thatching Ants for the character of debris on their nests. This species is polymorphic, with differing sizes. The smaller ants are likely the same species, from the same nest. Your caterpillar probably exuding something sugary to attract the ants, which would in turn, protect it from predators. Apologies if you already know all this.

  • Hi Kate,

    I do know that the ants tend the caterpillars to get “honeydew” and in turn protect the caterpillars from wasps and other predators. That’s probably why the caterpillars are able to hang out in the open like that. According to Life Histories of Cascadia Butterflies, “Most blue larvae have a “honeydew gland” on the seventh abdominal segment. About half our species are myrmecophilous (ant attended).” I know very little about ants, however, so thank you so much for the ID and for explaining that the smaller ants might be the same species. So many things to learn about—one can never get bored studying nature!

Leave a Reply

Post Categories
Notification of New Posts