Monthly Archives: July 2017

Forecast: A good year for “bad” lady beetles

I’ve been seeing a lot more aphids in northern Minnesota than I can ever recall seeing before, especially on Solidago (goldenrod).  I don’t know if there are really more than normal or if I’m just seeing them because I’m looking for lady beetles. If there’s one thing most lady beetles like, its aphids. If you find an abundance of aphids somewhere, you can usually count on some lady beetles showing up shortly to feast on them. Both adults and larvae will devour many of the plump, soft-bodied aphids in one day.  With the abundance I’m seeing, there should be a lot of lady beetles showing up soon. The problem is they will be mostly the wrong ones.

I’ve also been finding a lot of lady beetle larvae and pupae at one particular patch of wildflowers in west Duluth, and almost all of them have been pupae of Coccinella septempunctata, or 7-spotted lady beetle. Although native to Europe and Asia, by the end of August each summer they outnumber most or all of our native species.

Pupa, larva and adult of Coccinella septempunctata. Do aphids hear the Jaws theme when they see this coming?

While disappointing, it won’t be very surprising. Along with its fellow invasives Harmonia axyridis and Hippodamia variegata,  C. septempunctata has been increasing in the region ever since it first appeared some 20-25 years ago. When I conducted lady beetle surveys at nearly 70 northern Minnesota sites in 2014, 7-spotteds were found in nearly twice as many samples as any native species. As I walk through this patch of roadside flowers for hundreds of feet on July 31, I don’t see any other species.

The next day I visited another small patch of wildflowers in the heart of Duluth. Initially, I found the exact same thing, aphids everywhere but only 7-spotted lady beetles. Finally I spotted something different, a species of Hippodamia! We have at least 6 native species of Hippodamia in Minnesota, but I soon realized this wasn’t one of them. It was H. variegata, the variegated lady beetle. This is the most recent unwelcome addition to our lady beetle fauna, spreading through the western Great Lakes states by the early 2000s. By all indications it is still on the increase in Minnesota; it was the third most frequently encountered species in my 2014 surveys, more common than all but one native species.

 

Hippodamia variegata, Duluth, MN. August 1 2017

I didn’t have to look too much longer before I found the third and most well-known of our invasive lady beetles. Most people are all too familiar with the Harmonia axyridis, the multi-colored Asian lady beetle that invades homes and cabins in large numbers and makes a rather unpleasant house guest. They fly into lights and emit foul-smelling chemicals that also foul crops like grapes. They are large enough to deliver a noticeable pinch with their mandibles when handled. Along with Coccinella septempunctata they have been linked to the decline of several native lady beetles across eastern North America and all of Minnesota. Adalia bipunctata, Coccinella novemnotata and Coccinella transversogutta (2-spotted, 9-spotted and transverse lady beetles, respectively) have all declined severely in Minnesota, but we recently found that Hippodamia convergens (convergent lady beetle) has also declined.

We still have dozens of native lady beetle species in Minnesota, (most people think there are only 2 kinds: red and orange!) but it’s hard to say what the future will look like for native species. There are definitely more adventive species knocking at the door. Propylea quatuordecimpunctata is one such species. It has been found in Wisconsin but so far has not been reported from Minnesota.  Others are almost certain to follow.

Koch, R.L. 2011. Recent detections of a rare native lady beetle, Coccinella novemnotata
Herbst (Coleoptera: Coccinellidae), in Minnesota. The Great Lakes Entomologist 44(3-
4): 196-199.

Steffens, W. P. 2015. Rare Tiger Beetle and Lady Beetle Surveys in Minnesota’s Lake Superior Coastal Zone. Report to Minnesota’s Lake Superior Coastal Program. Project No. 13-306-05C. 25 p.

Steffens, W.P., R.P., Lumen. 2015. Decline in relative abundance of Hippodamia
convergens (Coleoptera: Coccinellidae) in fall shoreline aggregations on western Lake
Superior. The Great Lakes Entomologist 48: 159-162.

Steffens, W. P. and C. Little. 2014. Ladybugs of Minnesota Poster.  Created for Minnesota’s Lake Superior Coastal Program Project No. 13-306-05C. 25 p.

Williams, A.H., and D.K. Young. 2009. The alien Hippodamia variegata (Coleoptera: Coccinellidae) quickly establishes itself throughout Wisconsin. The Great Lakes Entomologist 42: 100.

 

©2017 Wayne P. Steffens

Parasites, anyone?

Ever felt as if something was eating you up inside? Ever had a gnawing feeling in your gut that something was wrong but weren’t sure exactly what it was? Ever wish you were a dragonfly and could just fly away from it all? You might want to reconsider that wish. For some helpful perspective on life’s troubles let me introduce the abdominal ailments of Macromia illinoisensis and Didymops transversa, aka the Swift River Cruiser and Stream Cruiser.

In 2013, dragonfly experts Ken Tennessen and Bill Smith were out north of Boulder Junction, Wisconsin looking for nymphs of Somatochlora cingulata (lake emerald) when they noticed something unusual. The M. illinoisensis nymphs they collected had something long and white coiled inside their abdomens. Although both Ken and Bill each had decades of experience collecting cruiser nymphs in Wisconsin and elsewhere, they had never seen anything like this before.

What Ken and Bill observed: Macromia nymph with ropy white coils inside. Photo © Dr. Ken Tennessen

They dissected some of the nymphs and confirmed their suspicions. The nymphs were being parasitized by some sort of nematode (round worm). Nematode parasites of dragonflies had rarely been reported before, and the two went on to confirm that the closely related Didymops transversa is also being parasitized in some Wisconsin lakes. The culprit is apparently a nematode in the family Mermithidae, and it does not seem to be hosted by any other type of dragonfly in the area. It may prove to be specific to the Macromiidae.

Macromia illinoisensis nymph dissected to show the nematodes within. Photo © Dennis Johnson

Mermethidae are a taxonomically difficult and poorly known group, as are most nematodes. They are somewhat infamous though because of Mermis nigrescens, a mermithid that parasitizes grasshoppers. That species lays its eggs on vegetation, and the grasshopper ingests the eggs which hatch and grow to great lengths internally. The parasite can grow to at least 6 inches in the body cavity, feeding on the hemolymph (blood) of the grasshopper. They then exit the body of the unfortunate dead..or living…grasshopper, and complete their life cycle in the soil.

This find opens an exciting new area of discovery in regional dragonfly biology, and is just one of several major dragonfly discoveries that Ken and Bill have been involved in. Their research team now includes Marla Garrison and Dennis Johnson, and I expect more interesting news from this group in the future.

Tennessen, K., W.A. Smith, M. Garrison and D. johnson. 2015. Nematode Parasites in Nymphs of Macromia illinoiensis in Northern Wisconsin Lakes.  Argia: 27 (1) p. 24-25. 

©2017 Wayne P. Steffens

The Aeshnas are coming

A rare (for this year) sunny Monday, and another dragonfly safari in northern Lake County Minnesota. I headed back north to where I collected Somatochlora brevicincta (Quebec emerald) for the first time about 10 years ago, hoping I might have similar luck. It was a pretty unexpected place for brevicincta, a rather wide and open channel with lilypads and such, the kind of place where I’d expect to see Libellula quadrimaculata (4-spotted skimmer) and Leuchorrhinia frigida (frosted whiteface) rather than brevicincta. But today I only found the former 2 species. I know the real breeding habitat for brevicincta is the peatland to the north, but I don’t have time to trek through the woods today. I’m more curious to find out how often they use this road. I don’t find any today.

However, just across the road I saw a small dark form flying low and secretively over the narrow trickle flowing through the ditch. Somatochlora minor! The channel it was patrolling was barely a foot wide. Although one of our more common emeralds, I never tire of the green eyes, brilliant yellow spots, and the places they inhabit.

Somatochlora minor male (ocellated emerald)

 

Farther up the road I stopped to try and catch an Aeshna feeding over the roadbed. I haven’t seen many Aeshna yet this summer, but as summer wears on they will soon be almost everywhere.  This one turns out to be the ubiquitous Aeshna canadensis (Canada darner) but several other species should appear here soon. Identifying some of the Aeshna (mosaic darners) can be tricky; if you’re still learning or want to learn to identify them the Wisconsin Dragonfly Society has a useful identification guide here.

I find some Somatocholora walshii a bit further up the road, and then head for home.I’ll come back looking for the rare A. subarctica  (subarctic darner) in August or early September. By then, most of the Somatochlora will be gone.

I follow a hunch. On my way home I stop near a swampy area that has always intrigued me but I’ve never sampled. It just has “the look” of someplace that might harbor interesting species, although I can’t quite put my finger on or elucidate exactly what that look is. Its just a mix of some black ash, white cedar, and black spruce. I stop the car when I see a medium-sized dragonfly feeding back and forth over the road. It evades me several times, but as it flies overhead I see the clear silhouette of a Somatochlora-dark, slender, steady and deliberate in its flight. Rather than fly up and down the road as I often see them do, this one zigs back and forth across the road, tacking gradually east. Then it reverses course and zig-zags back and forth heading west. After several maddening cycles and about 20 minutes of this game where it always senses my interest and avoids me, it finally makes a mistake. It comes down to waist level to grab an insect, then cuts across the road into my waiting net.

My patience paid off. Its another new location for Somatochlora forcipata (forcipate emerald), the third site that I’ve found them this year including my back yard, and without too much effort. As I said last week, they are there to be found by the patient and the lucky. I’ll have to come back and investigate where the breeding habitat is.

©2017 Wayne P. Steffens

Somatochlora hunting

Today we headed out toward the bogs and rivers of northern Lake County, MN not far from where I live. The goal, as it often is, was to find some Somatochlora and see what other dragonflies we could scare up. It didn’t take long.

Just a few miles up the road we stopped near a small river. I found one Somatochlora minor (ocellated emerald) dead in the road.  I have become pretty good at spotting roadkilled dragonflies, even when driving.  I once found a new Somatochlora hineana (Hine’s emerald) site near St Ignace, Michigan by finding a roadkill. With a little practice, dragonfly wings can be seen sparkling and flopping about in the wind as other cars pass.  I also saw some more emeralds flying overhead but couldn’t get my net on them.

Up past the Cloquet River is the real Somatochlora Country, where the wilder country that emeralds love really begins.  In the space of a few miles I found Somatochlora walshii (brush-tipped emerald), Somatochlora kennedyi, (Kennedy’s emerald), and the prize of the day, a female Somatochlora forcipata (forcipate emerald).

Somatochlora forcipata, the forcipate emerald

This is one of the least commonly seen emeralds and is considered rare by some. I believe they are merely more difficult to find. They are certainly uncommon, but not rare. This one was captured as it oviposited in a small roadside ditch puddle that was quite unremarkable. The primary breeding habitat might be sphagnum pools in nearby bogs, but I’ve also seen them repeatedly in areas where sphagnum is scarce or entirely absent, like my backyard at houses in both Minnesota and Wisconsin.

©2017 Wayne P. Steffens