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Pesty caterpillars remind me: know your system

Tiny masses of webs appeared seemingly overnight in our  young Burning Bush (Euonymus alatus) shrub.

Although the tent caterpillars are my go-to suspects whenever web-spinners appear on our plants, this time the caterpillars (attractive ones – creamy yellow with black heads and two neat rows of black spots) weren’t a species I recognized. I snipped off the branches bearing the offending critters and took a few shots before removing them from the garden.

A quick Google search didn’t turn up any good matches, so I posted the offenders on Bug Guide. A response came back in minutes, bearing with it a humbling reminder that I could have probably ID’d them very quickly on my own had I bothered to remember the host plant: this species is commonly called the Euonymus Caterpillar (Yponomeuta cagnagella), because its host is, of course, the burning bush. Both the plant and the critter are introduced (the former intentionally, as a horticultural plant; the latter, not so much – it’s been in North America only since 1967). An excellent synopsis of the natural history of the caterpillar has been produced by the University of Wisconsin Extension division: Euonymus caterpillar.

Others (Ted comes to mind the most) have written about the value of learning/knowing the hosts of the insects you come across, especially when it come time to IDing the insect of interest. Indeed, there are some species that are so remarkably similar that their host associations are the only way they can be reliably distinguished. I can think of at least one genus (which I first encountered in Missouri at BugShot last year ) that fits the bill: these lovely Membracids, which James Trager informed me were called Enchenopa-on-ptelea (Ptelea sp. being the genus of the host plant). Later that summer, I encountered another Enchenopa here in Ontario, but, being botanically disinclined, I wasn’t able to ID the host in the field, and therefore missed out on an opportunity to get a better ID on my insect.

On my “to-do” list for the next few years is to better acquaint myself with the flora of this region. While I can rattle off the names of a few common temperate trees and flowering plants, I am probably more familiar with the plants growing on the Arctic tundra than I am in with those in my own backyard (I spent considerable time during my first field season in the north learning to ID the common plant species there).

While that imbalance of expertise is very useful for my Ph.D research, it’s  a bit of a personal sore spot on the home front.  One of the most valuable tools a field ecologist can have in her toolkit is a solid knowledge of her study system, not just the particular organism of interest (i.e., the bug). The plants, animals, and non-living components (soil, water, etc.) of an ecosystem with which an insect interacts can tell you almost as much about your subject as the insect itself. I would be a much more effective ecologist/entomologist if I did a better job of dealing with my botanical knowledge gap (I’m open to field guide suggestions for northeastern North America!).

As much as it can be daunting, this is one thing I just adore about being a scientist: there is ALWAYS something new to learn!

Get your mothing on with National Moth Week!

National Moth Week

First National Moth Week – July 23-29, 2012

Well hello! Have any of you noticed how freaking nice it’s been outside?

I’ve been outside.

A lot.

And therefore have pretty much been entirely ignoring the Internets. But I’m back!

Since my last post was about a pretty little moth I found in my garden back in April (bad blogger!) I thought it was quite appropriate to re-start my summer posting with some exciting news for all you moth-lovers out there (generalist bug geeks also!): July 23-29 is officially National Moth Week. Although this venture is originating in the U.S., we Canuks have been invited to play too.

NMW is a great opportunity to get outside (um, it’s really nice out there), play around in the dark (minds out of the gutter, plz), take photos, record data, and enjoy some fun, hands-on citizen science! From the official website of NMW:

National Moth Week brings together everyone interested in moths to celebrate these amazing insects. This summer, groups and individuals from all the across the country [and Canada! and other countries!] will spend some time during National Moth Week looking for moths and sharing what they’ve found. Getting involved during National Moth Week is easy: attend a National Moth Night event, start an event, join friends and neighbors to check porch lights from time to time, set up a light and see what is in your own backyard, or read literature about moths, etc.

I registered an “event” (i.e., I’m going camping and taking my camera) just this morning – you should too! You know you’re probably already going to be hanging around your porch light in the evenings, so why not make it an official (and scientifically useful!) event?

I probably hang around my porch lights almost every night. I actually deliberately buy the really bright pure white floodlights, rather than the recommended yellowy ones that are supposed to keep swarms of insects from harassing you on your patio and streaming into your home every time you open the screen door. Keep the insects away? Pshaw! What’s the fun of that?

Despite all the time I spend looking at moths, I realized today as I waded through my photograph collection that I only have maybe 2 or 3 decent photos of moths. That’s it. I’ve only blogged specifically about a moth three times. Pathetic.

To rectify this sad state of affairs, I plan to get myself a copy of Seabrooke Leckie’s new Peterson Moths of Northeastern North America field guide (one can never have too many field guides – by the way, you can WIN a field guide if you register!). Then, when I return from my camping trip (which will be internet-free), you can expect some post-hoc blogging highlighting a moth or ten from each day of NMW.

Consider yourselves duly notified, and get yourself registered!

A weird, wingless discovery

One thing I love about sorting my trap samples is that I never know exactly what I’m going to see! Add to that the novelty of specimens from the far north, and the inherent diversity of insects, and it’s pretty much guaranteed that I’m going to see at least a few new-to-me species every time I sit down at my lab bench.

This term I’ve had an undergraduate student volunteer, Michael, working with me.  He quickly demonstrated that he’s not only interested but also talented, progressing from sorting to pinning and pointing specimens (a task I’m notoriously anal about and rarely relinquish to others – everything must look *just so* – but Mike has proven up to the challenge) in a few weeks.

He’s also got what I’d call a “good eye”.  While he may not know all the formal taxonomic names or anatomy of everything, he’s been quick to pick up on the visual cues and patterns of different groups of insects, and often points out interesting new things he finds in the samples he’s working on.

The other day, he looked up from his dissecting microscope and asked, “Do all wasps have wings?” He had been taught, you see, that two pairs of membranous wings was one of the defining characters of the wasps he was to extract from his samples.  “This looks like a wasp, but it doesn’t have wings.”  I came over to his station to take a peek and saw this:

Gelis sp., a wingless female parasitoid (Ichneumonidae)

A wingless female parasitoid wasp. Photo by Katie Sim (because I am useless at using our lab microscope camera and Katie can take great photos of tiny things like itsy-bitsy spider genitals. )

I saw that he had correctly nailed this critter as a Hymenopteran, and that, indeed, it had no signs of wings.  In a moment of blinding genius, the first words that fell out of my mouth were: “It’s an ant!”  Then, “No, wait…”  Although the tiny, reddish, long-legged animal did rather resemble an ant, the abdomen, mouthparts and antennae were all wrong. A wingless wasp it was! How cool!  I shared Mike’s excitement over the discovery, as this was a first for me as well.

I did some Googling and Bug Guide searching, and found that a number of parasitic wasp groups had wingless females.  (I also read that many of these were ant-mimics that would sneakily attack ant-tended hoppers and their nymphs, so felt somewhat better about my earlier ID gaffe).  Since there were too many possibilities, I called in the reinforcements: the post-doc in our lab also happens to be our resident wasp expert. Laura kindly agreed to take a look at the tiny critter and quickly confirmed her initial suspicions: it’s a member of the family Ichneumonidae, of the genus Gelis.  And that’s about as good an ID as we’ll get, because apparently the Gelis sp. group is ridonculously difficult to pick through.

As far as their diet goes, Laura had this to say: “They attack a variety of things, generally things in silk cocoons.  So, they can be hyperparasitoids on cocoons of Ichneumonoidea, or primary parasitoids on spider egg sacs or small Symphyta and Lepidoptera cocoons”.  So much for my maybe-it-looks-like-an-ant-so-it-can-attack-ant-tended-hoppers theory.  This wasp’s winglessness may therefore be a reflection of her preferred food sources: egg sacs or cocoons attached to low-lying vegetation are perhaps easier to access by land, rather than by air.  By not “wasting” energy on the development of wings or on flight, the female wasp might be able to devote more energy to the production of her eggs and eventual offspring.

I love this little discovery in part because parasitoids are awesome and wingless parasitods are extra-cool.  But I think I love it MORE because it involved the combined efforts of four people to pull all the pieces together (thanks Mike, Katie and Laura!)

“A most variable species,”…

…writes Lindroth (1969) of Pterostichus (Stereocerus) haematopus in his 1200+ page taxonomic key of Canadian/Alaskan ground beetles.

“Black…upper surface as a rule with metallic lustre (bluish, green, brass or coppery)…”

Pterostichus (Stereocerus) haematopus - black/metallic version - dorsal

Black with greeny-metallic lustre – check.

But, lo:

“…elytra sometimes rufinistic [reddish]”.

Well that’s quite different, isn’t it?

Pterostichus (Stereocerus) haematopus - rufinistic version - dorsal

Ok, reddish – check.

These two again from the side:

Pterostichus (Stereocerus) haematopus - black/metallic version - lateral

Pterostichus (Stereocerus) haematopus - rufinistic version - lateral

Believe it or not, these two beetles are the same species. This is a great example of why a well-assembled taxonomic key is critically important to making accurate identifications. I had rough-sorted (i.e., “guesstimated/eyeballed”) these beetles into different groups initially, but the reddish-brownish one (of which there are few) just kept keying out the same as the more prevalent metallic version. I checked in with the experts at the Canadian National Collection to make sure I hadn’t goofed – and I hadn’t.

The key I’m using for my ground beetles was written by Charles H. Lindroth over the course of about eight years, and represents the sum of several “smaller” publications. It is truly a magnum opus in the world of beetles (indeed, of entomology) and is still considered the ultimate reference for this family, even after 35+ years of new research and updated phylogenetic/taxonomic work.

(For Morgan: Taxonomy FTW!)


Lindroth, C.H., 1961-1969. The ground-beetles (Carabidae, excl. Cicindelinae) of Canada and Alaska. Opusc. Entomol. Suppl. 20,1-200; 24,201-408; 29,409-648; 33, 649-944; 34, 945-1192; 35, I-XLVIII.

Mind-controlling beetle parasite

This post was chosen as an Editor's Selection for

I’m sorting through beetle specimens collected from Iqaluit, Nunavut today.

There’s not a ton of diversity in the samples so far, and I was starting to get a little bored, until I saw this:


Say it with me now: “EWWWWWWWWWW“.

Now say, “COOL!”

Very good.

This poor ground beetle (family Carabidae) has been parasitized by a nematode-like worm called a hairworm, or “Gordian worm”, (Gordiaceae: Nematomorpha).  Adult hairworms are free-swimming, water-dwelling animals (either in fresh or salt water). They mate and produce young (larvae) in the water.  The larvae require two hosts. First they infest various small arthropods (called paratenic hosts), like mosquito larvae. Next, those small paratenic hosts are consumed by other, larger arthropods – ground beetles fit the bill since they are heavy-bodied, voracious predators.  Worldwide, at least 70 species of ground beetles are known to be hosts for hairworms.

When the worm is mature, it has to leave its host and return to the water to reproduce. If it has infested an aquatic insect, it has no trouble making its way back to the water. However, if it has chosen a terrestrial insect as a host, things get a little more complicated.

Like so many parasites, the hairworm can use a type of mind-control to affect the behaviour of its host. In this case, it compels the terrestrial beetle to seek out water, then drown itself. Yikes! For this beetle, which I caught in a yellow pan trap, I can envision one of two scenarios: 1) the worm was mature, and convinced the beetle to take a dip in the preservative fluid in the trap, or 2) the beetle just happened to wander into the trap, and the worm decided to abandon ship. Whatever happened, it was not a happy “ending” for either animal!


Not a happy ending.

Poinar G Jr, Rykken J, & LaBonte J (2004). Parachordodes tegonotus n. sp. (Gordioidea: Nematomorpha), a hairworm parasite of ground beetles (Carabidae: Coleoptera), with a summary of gordiid parasites of carabids. Systematic parasitology, 58 (2), 139-48 PMID: 15449829

I selected this post to be featured on my blog’s page at Nature Blogs.
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