Summer Strolls in Streams, Part 3

I’d never seen these “hammerhead flies” (Diopsidae: Sphyracephala) before this summer, but I encountered them several times in August while walking along streams. I’m not sure why they would be associated with streams specifically; apparently the larvae feed on decaying vegetation, and according to Steve Marshall’s Insects: Their Natural History and Diversity, adults are found in “swampy areas”; one of the two North American species, S. brevicornis, “overwinters in the adult stage and can often be found around skunk cabbage in early spring or late fall.” That’s all the information I’ve found about them so far. Here are some congregating on a leaf overhanging the Mill River on August 20:

Maybe someday I’ll meet them when I have a proper camera/lens in hand, but for now, this is what we get.

Despite its limitations, I’m loving this camera’s (the Olympus Stylus TG-4) ability to take pictures underwater. I wish I’d had back when I was spending every spring conducting surveys of vernal pool amphibians. Here’s a crayfish in another stretch of the Mill River, also on August 20:

Later that day, on the North Branch of the Manhan River, the pupal skin of a big crane fly (Tipulidae) poking out of the liverwort-covered streambank:

This crane fly I found ten minutes later may or may not have been what emerged from that pupa:

On the way back to the car from that site we met this American pelecinid wasp (Pelecinidae: Pelecinus polyturator). The larvae of this species are parasitoids of the grubs that turn into junebugs, or May beetles, or whatever you want to call them.

There was a little stream in Whately that was almost totally dry on our second visit, but when we came for our final visit on August 20 there was more water than ever. Lots of millipedes were congregating on emergent stones, seeking higher ground…

…and some that had chosen the wrong stones were still clinging to them underwater.

This group was joined by a slug. I don’t know how long these things can survive underwater, but it seemed like the water level must have gone up shortly before we arrived.

August 21, along the Middle Branch of the Westfield River: a dobsonfly egg mass attached to an overhanging boulder.

And a nice bit of exposed bedrock in the riverbed.

Later that day, I found a few larvae of the sawfly Tenthredo grandis (Tenthredinidae) on their host plant, turtlehead (Plantaginaceae: Chelone glabra), along the shore of the Whiting River.

I hadn’t seen one of these beauties in 16 years, so of course I brought a couple home for some better photos.

August 22, along Clesson Brook: a caddisfly infected with the fungus Erynia rhizospora, which causes its hosts to die plastered to rocks overhanging streams, aiding the pathogen in spore dispersal.

This crane fly has succumbed to a similar fate, presumably infected by a different fungus that is specific to crane flies.

And this fungus victim appears to be a yellowjacket or something like that. There seems to be a fungus for just about everybody, as evidenced by this gallery I’ve been maintaining on BugGuide over the years.

August 24, on the East Branch of the North River: a boulder that has been popular with the dobsonflies over the years. Each of the ~30 white rings is the remnant of an egg mass (like the one above) that contained up to 1000 or so eggs.

Here’s a close-up of the main cluster:

Please correct me if I’m wrong, but I’m thinking this is the shed skin of a caddisfly pupa that wriggled out of its case and crawled up the side of a boulder so that the adult could be out of the water when it emerged.

Later that day, somewhere in Rowe: eggs of a caddisfly (Limnephilidae) in a jelly matrix, deposited on a mossy bank overhanging a stream, into which the larvae will drop when they hatch.

Also a red eft (the terrestrial juvenile stage of the eastern newt)…

…and a footprint of a small black bear.

As it happens the next site we visited that day was the Cold River in Florida, where we’d seen a bear during our first visit. This is the slope we’d watched the bear scrambling up a few weeks earlier:

August 26, another big footprint—this one left by a beaver on the bank of the Konkapot River.

A mayfly resting by the Green River in Great Barrington (I’m told it’s Isonychia bicolor, same genus as the exuviae in my previous post):

And this was news to me: a native insect (the caterpillar of the pearly wood nymph, Noctuidae: Eudryas unio) that feeds on purple loosestrife (Lythraceae: Lythrum salicaria). It also feeds on the native swamp loosestrife (Decodon) and members of the evening primrose family (Onagraceae).

Along a little stream in Lenox, some sawfly larvae devouring a willow leaf (these, too, were added to the menagerie in jars on my desk):

Along the East Branch of the Housatonic River, a black and yellow mud dauber (Sphecidae: Sceliphron caementarium) on its way to daub some mud:

August 28, last visit to the Fort River: Sometimes it was hard to picture how a dragonfly nymph managed to get itself to the spot where I found its empty skin clinging, like this one that was at the tip of a long root dangling over the water:

Along the Middle Branch of the Westfield River, another caddisfly egg mass—this one more recently deposited (in the first one the eggs didn’t look as round because the embryos were pretty far along).

And that’s a wrap! (Well, there were some other interesting leaf mines, but I’ll wait till I have the full story on those.)

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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6 Responses to Summer Strolls in Streams, Part 3

  1. Lisa Dolliver says:

    Lovely to come along on your hike this morning. Just the sort of knowledgeable guide that makes a walk unforgettable.

  2. Tom says:

    Great pics, as always. Maybe the hammerhead flies hang out around skunk cabbage because it generates its own heat. That would be an advantage, I would think, to a species that overwinters as an adult.

  3. Laura Hughes says:

    Great posts! I too have only ever seen stalk-eyed flies sitting under leaves above a stream. Sometimes in large aggregations.

  4. brewbooks says:

    Thanks for an interesting view of some natural history of (I think) Massachusetts. I had hoped to explore some of this state on a planned thru hike of the Appalachian Trail in 2020. Alas, that didn’t happen. My new plan is to thru hike the AT in 2022. Meanwhile, your posts are a great way to learn more about nature in my armchair.

  5. Anonymous says:

    A fun trip with you again! Thanks!

  6. Linda G. says:

    What a fabulous post. The diversity is exciting, the photographs are astonishing to behold! Thank you!

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