Summer Strolls in Streams

Looks like it’s been a month since my last post. In that time I’ve made some great progress on my new guide to sawfly larvae (finished the preliminary literature review and ready to start putting together species accounts); revised and updated another chunk of the leafminer guide (I’ll be sending out the chapters up to and including the legumes shortly); and I’m now putting together an online course about how insects and other invertebrates make it through the winter (you can check that out here—apparently it’s almost full already, but if more people sign up we’ll add another session).

But right now I have to take a little break from all those things to put together a report that’s due at the end of the year. This summer the Massachusetts Natural Heritage & Endangered Species Program hired me and Julia to conduct surveys for an uncommon dragonfly, the ocellated darner. Our surveys consisted of slowly walking up 100-meter stretches of streams and small rivers, collecting all the exuviae (shed skins) left behind by emerging dragonflies when the nymphs crawled out of the water and molted to adults (as shown here). This fall, Julia got to go through all the exuviae we collected and identify them to species, and then enter all our data into a database, and now it’s my turn to work on putting the report together and submitting our data to NHESP. Part of that is going through and organizing all the photos I took of our survey sites. And part of that process is weeding out the “extracurricular” photos. So here’s the first batch.

July 24, Middle Branch of the Westfield River: Cimbex americanus (Cimbicidae), among the chunkiest of all sawflies, rests on a stone at the edge of the river, apparently having just emerged from a harrowing tumble down the river, which claimed parts of its left antenna and wing. This species is known as the “elm sawfly,” but it is actually one of the few sawflies whose larvae feed on foliage of a variety of unrelated trees.

July 27, Whiting River: A leaf of some kind of beggar-ticks (Asteraceae: Bidens) bejeweled with dew, and sporting a leaf-mining larva of a species of Calycomyza (Agromyzidae)—possibly C. avira, which Owen Lonsdale and I described two years ago.

Just a few feet away, some leaf mines on purple-stemmed aster (Asteraceae: Symphyotrichum puniceum) made by larvae of Microrhopala xerene (Chrysomelidae), a striking black beetle with red racing stripes.

And dotted along the shore of that same stretch of river were mines on miterwort (Saxifragaceae: Mitella diphylla) made by what is probably an undescribed species of Phytomyza. (Julia and I collected and reared this species in Iowa last summer but Owen hasn’t had a chance to examine the specimens yet.)

I mostly had been leaving the camera in my backpack at this point in the season, but on this day I decided to keep it in my pocket to get a few pictures of the dragonfly exuviae in situ. The first one I came to was from a nymph that had climbed several feet up a hemlock tree to make its transformation. Some time after the adult had emerged, the shed skin had fallen and become caught in a spider web, and a gypsy moth was now laying her eggs behind it.

This stream had a population of green frogs that liked to hang out on ledges many feet above the water level. There is one tucked into a corner just above the middle of this photo, looking right at the camera.

Here’s how we often found the exuviae: clinging to the mossy ceilings of overhanging rock ledges. If you look closely at this skin you’ll see a little orange gall midge (Cecidomyiidae) resting on its abdomen.

July 27, Hubbard River: At the downstream end of this transect (where I had to stand and hold the measuring tape while Julia measured out 100 meters), there was a lovely sedge-covered island with a big patch of cardinal flower (Campanulaceae: Lobelia cardinalis).

Also on this island was a big witch hazel (Hamamelidaceae: Hamamelis virginiana) covered with galls caused by an aphid, Hamamelistes spinosus. Evidently these galls drip with honeydew, because the bush was abuzz with bees and wasps visiting the galls as if they were flowers. My little pocket-sized point-and-shoot was no match for these bugs that were in constant motion, but the photos below give you some idea. I think this first one is a potter wasp (Vespidae: Eumenes, or so)…

…and there were lots of common eastern bumble bees (Apidae: Bombus impatiens).

After we finished each survey, it was my job to walk transects across the stream and (among other things), at regular intervals, measure the water depth and characterize the substrate. On one of the points along my first transect on August 6, the substrate was a wood turtle! This is another uncommon species that NHESP keeps track of, so I ran the 100 meters back to my backpack to get the camera. I had never used this camera’s underwater mode before, but it went pretty well:

From that point on, I kept the camera in my pocket at all times, so the pictures of miscellaneous bugs and things became more frequent. Had I started doing that a week earlier, I could have also gotten pictures of a bear scrambling up a steep slope overlooking one of the streams we surveyed in the Berkshires.

August 6, North Branch Manhan River: a fishing spider (Pisauridae: Dolomedes vittatus) resting on a vertical rockface.

Hard to appreciate the size of this spider without something for scale:

And a side view reveals that she was carrying an egg sac under her body:

August 9, back on that the stretch of the Whiting River that had all those nice leaf mines and frogs: shortly before we arrived, a wading great blue heron had stepped out of the water and left these wet footprints across a boulder.

Also at that site, I met a strange fly I’d never seen before. I called it a “hammerhead fly,” which turned out to be on the right track: it’s a “stalk-eyed fly” in the genus Sphyracephala (Diopsidae), which is Greek for “hammerhead.” The “stalk-eyed” name is better applied to diopsids found in other parts of the world, as seen in this Wikipedia article.

Later that day, back at the stretch of the Hubbard River with all the cardinal flowers and witch hazel galls: a shed skin clinging to the underside of a totally mossless rock. It’s amazing to me that the nymph was able to cling upside down to this surface at all, let alone stay there for an hour while an adult dragonfly slowly squirmed out of its back, and then continue to cling there as an empty husk for days afterwards.

That’s how far I got as I went through the summer’s photos last night. More to come!

About Charley Eiseman

I am a freelance naturalist, endlessly fascinated by the interconnections of all the living and nonliving things around me. I am the lead author of Tracks & Sign of Insects and Other Invertebrates (Stackpole Books, 2010), and continue to collect photographs and information on this subject. These days I am especially drawn to galls, leaf mines, and other plant-insect interactions.
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4 Responses to Summer Strolls in Streams

  1. enallagma9 says:

    Looking for shed odonate skins is one of the under-rated pleasures of this world. You see so much else at the same time! And if you want to be truly amazed at the clinging abilities of the nymphs, go check for skins under a protected bridge come February – there will still be Boyeria skins hanging on!

  2. Wonderful variety of observations. Good luck with the book!

  3. Anonymous says:

    I seem to recall that in some parts of the world, some species of jumping spiders repurpose the shed skins of Odenata, using them as refuges.
    A million thanks for posting the photos of the wood turtle. When I lived in New England, I dreamed of finding one, but never had the good fortune to do so. It is such a treat to see photos of one that you found.

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