The Bug Geek

Insects. Doing Science. Other awesome, geeky stuff.

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!

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4 responses to “Pesty caterpillars remind me: know your system

  1. Dave June 11, 2012 at 10:10 AM

    Interesting mini-ecodisaster: ‘le Grand hyponomeute du fusain’ (Charcoal Grand Ermine?) or Spindle Ermine also feeds on Euonymus ‘native; to North America and is only one of several Yponomeuta that have made it to North America in recent decades to feed on our wahoo, apples, cherries, saskatoons, etc. Does make one wonder if the American Ermine Moth larvae Yponomeuta multipunctella feed on the introduced Euonymus and what the parasitoids think about the newly arrived cousins of their host? There’s a research project in just about every bug sighting!

  2. Matt June 13, 2012 at 12:01 AM

    Newcomb’s Wildflower guide is my favourite flower field guide for the Northeast. I’ve been using it for several years now, it’s code-key allows for very quick identifications.

    After several years of hunting for flower species myself, I have found it to be a very rewarding endeavour for its own sake (and not just for better insect ids). ‘Collecting’ images of wildflower species is a lot of fun, and goals such as ‘all species in Ontario’ are very attainable, whereas insects (though awesome as they are) are a black hole of things to learn and see. In short, my plant photography has complemented my insect photography very well.

    Happy flower hunting!

  3. Jeanette June 19, 2013 at 4:40 PM

    I found these on a milkweed plant. Would they be the same?

    • TGIQ June 22, 2013 at 8:32 AM

      It’s more likely to be a similar-looking species; milkweeds are quite toxic and the insects that feed on them are highly specialized. Monarch butterfly caterpillars and Milkweed Tussock caterpillars are commonly seen on milkweed – likely you found some of those!

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