Exciting Day at Spring Prairie

A rufous hummingbird nectaring on Cooley’s hedgenettle

An Anna’s blue on a fading lupine. I’ll have to come back when they are in bloom to try to ID the lupines.

On July 25, Nancy Bray and her husband, Herb, invited my husband Jim and me to join them on a trip to Blair Lake and nearby Spring Prairie. It was a bit hazy from fires to the south but otherwise a lovely day. When we got to the intersection of Road 733 that goes up to Spring Prairie, we made a quick decision to go up there first. I was pleased to see the road was in better shape than I remembered (no more trench down the middle of one section) as it had been quite some time since I’d driven up there although I had walked up the trail from Blair Lake last year (see Beargrass Season at Blair Lake).

We drove straight up to the edge of Spring Prairie and parked the car. On getting out, I immediately noticed lots of butterflies flying about in the large, mostly beargrass (Xerophyllum tenax) meadow. Other than some fireweed (Chamerion angustifolium) blooming farther downhill, nothing was in flower. So what were all these butterflies doing here? Growing among the beargrass was quite a bit of lupine (Lupinus sp.) with immature fruits. The butterflies all seemed to be Anna’s blues (Plebejus anna). If you guessed that they use lupines and other legumes as host plants, you’d be right. They appeared to be mating and laying eggs. I started searching the plants carefully. It took only a few minutes to spot the first egg, looking much like a tiny white sea urchin shell after the spines fall off. I’d never seen one before, but I recognized it from the similar hedgerow hairstreak eggs I’d seen a couple of years ago. What a great start to the day! I continued to look for eggs and found quite a few more, laid on stems and pods as well as leaves.

Jim admiring the view from the seemingly endless beargrass on Spring Prairie (I’m looking south, he’s looking west). It appears the beargrass didn’t bloom much this year. You can see some of the smoke coming from the Jack Fire on the North Umpqua.

The eggs of gossamer wing butterflies (blues, coppers, elfins, and hairstreaks) are flattened disks with a textured surface. I’m not sure what the benefit of the texture is, but it is beautiful.

While I was busy trying to photograph eggs and butterflies, everyone else was up on the road trying to ID the conifers. Once I was satisfied I had a decent photo of an Anna’s blue egg, I joined them. They were gathered around a subalpine fir (Abies lasiocarpa). This species can be distinguished from other firs by the way their needles go around the stem like a bottle brush. They often have a very narrow crown, but when growing in especially exposed places, they tend to be rather squat and have a wide skirt of branches around the base of the tree. Both forms are adaptations to living in areas of high snowfall.

Walking up close to the tree to examine the needles, I was surprised and excited to see the yellow growth of a conifer mistletoe (Arceuthobium sp.) on some of the branches. I’d only seen an Arceuthobium once before, years ago at Horsepasture Mountain, but it was lying on the trail, having broken off some branch above. I had perhaps wrongly assumed the mistletoes usually grew too high in the trees for me to see.

This mistletoe is growing on a subalpine fir branch. All the ones we saw were yellowish like this.

With the search image in my head, I went looking for more mistletoe. We headed over to where the trail down to Blair Lake meets the road and walked through the woods down to Beal Prairie, another large beargrass meadow, where we stopped for lunch. On the way, I found at least 5 more trees with what appeared to be the same kind of mistletoe. Some were on mountain hemlock (Tsuga mertensiana), others on fir (Abies sp.). Earlier in the year, I had been working on editing the treatment of Viscaceae, the mistletoe family, for Volume 3 of the Flora of Oregon, so it was really great to finally get to study it in person. Alas, I’m still not sure which species it is! The main difference in the key seems to be the host, but several species use the same host and some use more than one host. How confusing! My best guess is Arceuthobium tsugense, which uses both Abies and Tsuga as a host and is often yellow-green like these.

This mistletoe, on a mountain hemlock, is starting to fruit.

The first caterpillar I found had very small ants tending it.

The excitement wasn’t over. When we reached Beal Prairie, Jim, Nancy, and Herb sat down to eat lunch. I tried to sit and eat, but I noticed that there was a patch of lupines nearby. I simply had to check it for butterfly eggs. Instead of an egg, I spotted a caterpillar! And, it was surrounded by tiny ants! So much for lunch. I kept looking and found two more caterpillars, and each was tended by ants. What was really of interest to me was that while the caterpillars all looked alike, each set of ants appeared to be a different species. I know very little about ants and don’t have any idea how many species there might be in the Cascades. But my interest is certainly piqued now!

The caterpillars were definitely the slug-like ones of a gossamer wing (family Lycaenidae), but I couldn’t be sure which species until I got home and checked Life Histories of Cascadia Butterflies. They looked a lot more like the caterpillar of a Boisduval’s blue, with more patterning than the plainer green caterpillar of the Anna’s blue. Boisduval’s blues seem to feed exclusively on lupines, so this was not at all surprising. I e-mailed David James, one of the authors, and he agreed. It seems that the Boisduval’s must reach maturity earlier than the Anna’s, which were just beginning to lay eggs only a few hundred feet higher in elevation in Spring Prairie.

The second caterpillar had a medium-sized ant.

The third one had a large, red and black ant. Is this starting to sound like “Goldilocks and the Three Caterpillars”?! The subtle pattern on the caterpillar’s back makes it likely this is a Boisduval’s blue rather than an Anna’s blue as I first guessed.

David is also interested in ant tending, which has been confirmed for a number of different species of blues but not all of them. He suggested I return to Spring Prairie several weeks later to see if I could find the Anna’s blue caterpillars and see if maybe they were ant-tended as well. Very unfortunately, just a few days after our trip, a thunderstorm came through and started a number of fires in the area, include the Kwis Fire along Salmon Creek Road just east of Oakridge—the road needed to access the area. It has been off-limits ever since. And the smoke from all of the fires has been blowing around the Middle Fork district for a couple of months, making any hiking unpleasant and unhealthy and pretty much ending my botanizing season much earlier than normal this year. But returning to Spring Prairie to look for more eggs and caterpillars will go high on my to-do list for next year. I’m really hoping there are no fires in the area next year!

Herb and Nancy by the edge of the north lake. The white flowers in the water are arumleaf arrowhead. It’s not that common in the area (check out the OregonFlora map here), so I always enjoy finding it in bloom.

The three-parted flowers and arrowhead-like (sagittate) floating leaves of arumleaf arrowhead are quite distinctive and just beg to be painted as well as photographed. Someday….

While there were no more big discoveries for me the rest of the day, it was still very enjoyable. I showed everyone the sweet little lake hidden just off the road on the way back. It’s about 1.2 miles from the trail intersection. It was filled with blooming arumleaf arrowhead (Sagittaria cuneata), and the wetland along the edge was also very floriferous. A mass of magenta Cooley’s hedgenettle (Stachys cooleyae) was the scene of many skirmishes of territorial rufous hummingbirds. Butterflies flitted about. It was a very lively and beautiful spot. Jim and Herb headed back to the road first and saw a pika in the rocks below the road above the second lake, which is farther downhill. I was too late to see it, but I did hear its cute muffled calls from under the rocks. I can hardly wait to get back to the area next year to look for eggs, caterpillars, and butterflies, check out the second lake and nearby wetland and rocky areas, and just enjoy a terrific spot for easy botanizing and butterflying.

4 Responses to “Exciting Day at Spring Prairie”

  • Ingrid:

    What a wonderful day for you and the macro photo of egg is amazing. Finding the many different ants tending the caterpillars makes me wonder what they are doing.

  • Janie Thomas:

    Very cool Tanya. We’ve hiked that area many times but didn’t know about the hidden lakes. Next spring!! Thanks

  • Kate:

    Tanya, you probably already have this figured out, but ant species “tend” caterpillars that exude a sweet solution through a dorsal nectary gland. There’s a lot of online info. Apparently this is not uncommon among some Lycaenid butterfly larva. In exchange, of course, the ants protect the larva from predation.

  • Kate, yes, I wrote about this last year in Butterfly Discovery at Eagles Rest. It’s a fascinating case of symbiosis that I first read about in a British butterfly book as a child. I’ve only seen it in the field a few times, however, so it is still exciting to witness.

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