The Bug Geek

Insects. Doing Science. Other awesome, geeky stuff.

Category Archives: Field work in the North

A trio of beautiful beetles

This fall I spent some time under the tutelage of some of Canada’s best-known entomologists at the Canadian National Collection of Insects, Arachnids and Nematodes, with the specific goal of confirming some of my identifications of Arctic ground beetles (Carabidae).

One researcher, Dr. Henri Goulet, currently works on sawflies (Hymenoptera) but he started his entomological career as a beetle guy. His insights and identification “tips” for my beetles were amazing.  Dr. Goulet also knows a thing or two about capturing insects – not with traps, but with his camera. He’s compiled hundreds of photographs of Canadian ground beetles for the Canadian Biodiversity Information Facility.

During my first summer in Nunavut, I was fortunate to collect a good series of a ground beetle called Blethisa catenaria. It was formerly known by only 4 other specimens, all over 50 years old; I found just over 30 more.

One of the wonderful things my collection taught us about this species is that they come in several colours. You’ll recall that I wrote a post not long ago on the color variation in another Arctic beetle, Pterostichus (Stereocerus) haematopus. Blethisa catenaria provides another great example – except it is decidedly SHINIER. Says Dr. Goulet about the variation in B. catenaria: “Based on your specimens, the color forms are not discrete, but gradually shift from dark to either green or copper”. Cool!

Dr. Goulet was very excited to get some photographs of the different color morphs of B. catenaria, and just this week he completed his work on the images. With his permission, I’m sharing them with you now:

Blethisa catenaria ("brown") - Photo by: Henri Goulet

Blethisa catenaria ("dark") - Photo by: Henri Goulet

Blethisa catenaria ("copper") - Photo by: Henri Goulet

SHINY!

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Arctic beetle trophic structure and shiny new research direction!

I am pretty excited by the next step I’m taking with one of my projects.

I’ve spent the past few months looking at a season’s worth of subarctic beetles from my summer in Kug, back in 2010. In my mid-field-season post that year, I mentioned that the community of beetles seemed pretty darned weird, at least to the naked eye: my traps were full of predatory beetles, but I was hard-pressed to find many herbivores, either in my traps or just by looking around on plants.

Now that I’ve actually gone through all of the samples, it’s clear that what I thought I saw was actually pretty much the case. Out of exactly 2638 adult beetles, 88.3% of them are carnivores. Only 11.2% are plant-feeders of some kind, and less than 1% are scavengers. I see almost identical figures if I consider the animals in terms of their mass and not just their numbers: about 87% of the “bulk” of all beetle bodies is carnivorous.

So why is this so weird?

Usually, when we think about how animals feed on each other, we tend to think of something rather pyramid-shaped, like this:

This is the “trophic structure” of a typical community of organisms. Each level in the pyramid is called a trophic level.

Most places on earth have a lot of plants. There are enough plants to feed, and provide energy to, all of the herbivores. Those herbivores are eaten by, and provide energy to, predators, which are fewer in number. Some trophic structures may have an additional level of “top” predators, that feed on just about everything, including other carnivores.

You can see how each trophic level in the pyramid gets smaller; it’s what keeps the community stable. For example, if there were more herbivores than plants, the herbivores would eat all of the plants (obliterating that level) and then they would in turn die off because there was nothing left for them to eat.

What I have found with my beetles from Kug is a trophic structure shaped something like this:

There are still quite a lot of plants, though not as many as you’d normally find in, say, an old open field in rural Ontario (this is the Arctic, after all). But the rest of the pyramid has essentially inverted: there are few herbivores and lots of predators.  The usual upward flow of energy seems to be disrupted.  Where are all these predators getting their energy?

My answer at this point is: I have no idea.

But I have two guesses:

1. Maybe I’m not seeing the whole picture – the predators might be eating other things!

Beetles don’t necessarily feed on other beetles. Maybe, if I added in other groups of animals, the trophic structure might look a little more “normal”. I don’t actually think this will be the case. I have started to look at the other critters I collected in my traps, and MOST of them are large, heavy-bodied, predatory spiders. There are a smattering of plant-eating bugs, grasshoppers, caterpillars and springtails, but I am almost certain there are not enough to provide energy to all the “bulk” of beetles and spiders.

2.  Who needs herbivores – why not just eat other carnivores?

I think these beetles (and the spiders, too) are actually feeding on each other  – this is a type of cannibalism, called intratrophic predation. In this kind of arrangement, predators get their energy by feeding on other high-energy predators. This is not unheard of; it’s been seen in desert communities, for example, but these kinds of trophic structures are not terribly common.

Anyways, I’d like to figure out exactly what’s going on in this system, and particularly if my second guess is correct. Since I wasn’t able to directly observe what all these beetles were eating while I was up north, I have to rely on some fancy-schmancy and new-to-me lab techniques

(*Gasp!*  TGIQ doing lab stuff??!?  I know, right?  This is all in the name of trying out new binoculars, friends).

The technique I’m going to start working on soon is called stable isotope analysis.

I’ll save the inner workings of this method for another post (not just a little bit because I’m still sorting out all the details myself!), but I’m pretty excited about trying it out. My job will be to carefully prepare beetle specimens by drying, crushing, and weighing tiny samples of their bodies into special teensy little tin cups. Then I’ll send them out to a lab that has a couple of specialized bits of equipment (which, last time I checked, I did not have sitting on my lab bench) that will measure the amount of nitrogen and carbon in each sample.

In a nutshell, this technique should let me figure out the trophic levels of all my predators (i.e., where exactly on the pyramid they sit), mainly by the amount of nitrogen in their bodies.  If they’re eating only herbivores, they’ll have less nitrogen, and will be on a lower trophic level. If they’re eating only other predators, they’ll have lots of nitrogen, and will show up at the highest level. Beetles eating a mix of herbivores and other predators will show up somewhere in the middle, with an in-between amount of nitrogen.

If I see mostly herbivore-feeders, and not predator-feeders, then I’ll know that my guess #2 is incorrect, and that I’m missing a piece of this little trophic puzzle.

Stay tuned for updates in the new year on this project!

Crushin’ (on) hoppers

Working working working…the fruits of my labours look like this these days:

A bunch of beetles from Kug…SHINY!!!

I”m also trying to get some more photog practice before BugShot (I just booked my flight 10 seconds ago, WOOT!), but it’s been so gad-dang-awfully hot around here that I can hardly stand to be outside for more than a few minutes.  That said, I’m still spotting some nice little critters in my yard, and currently have a great big crush on hoppers:

 

Unknown Spittle Bug - (Cercopidae)

Metcalfa pruinosa - Citrus Flatid Planthopper

BugShot 2011

I’m sitting in the airport in Calgary, waiting for the last leg of my southward journey home and enjoying some fine high-speed internet, of which I have been cruelly deprived for weeks.  Our collection efforts in Kug were great, and I’ll be posting about the trip soon, but I have NEWS that I simply must share.

As many of you know, there is an upcoming gathering of bug macrophotography epicness: BugShot 2011.  This event promises to be full of awesome and I have been holding my breath for weeks waiting to find out if a student fee waiver would enable me to go.

 

I am TOTALLY GOING.  (Now I just have to figure out how to get there :-P).

Woot!

My portfolio submission for the waiver is right here on Flickr. Thanks a million to all the people who took the time to look at, and offer their opinions on, my “short” list of candidates!

Life in the ‘Knife

Too tired to do a proper post on everything that’s been going on, so here:  this will have to do for now.

As of five minutes ago, our gear is packed, our specimens are in the mail and my team is heading up to Kugluktuk, Nunavut, tomorrow.  This is where I spent my summer last year, and it’s going to be nice to be on familiar turf.  That said, Yellowknife is a truly kick-ass city, the wilderness is spectacular, and I am one sad puppy about leaving it all behind. 

 

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