Baltimore Checkerspots – Caterpillar, Adult, and Parasitoid

2016 September 7

I found this spiky orange-and-black caterpillar crawling across the road on May 31, 2016. It was about an inch long, so not too huge as caterpillars go.


Those spikes are similar to what I’ve seen in several other butterflies, most notably the fritillaries and mourning cloaks, so I figured it was related to them.


Going through our book on Michigan butterflies, it looked like the caterpillar of one of the Checkerspots, most likely the Baltimore Checkerspot, Euphydryas phaeton, although it also looked a fair bit like Harris’s Checkerspot, Chlosyne harrisii. But as for which one, we’d need to rear it to find out.


It made a chrysalis within a couple of days after catching it, and at first things looked OK.



However, what came out after about two weeks wasn’t a butterfly. Instead, we got this:


While this is an interesting parasitoid wasp (probably one of the thousands of species of ichneumon wasps), it clearly doesn’t help us at all in identifying the caterpillar.


It left the chrysalis practically undamaged aside from the exit hole just behind the eye.


So anyway. No positive ID on that particular caterpillar. But, we do have some circumstantial evidence in that right about this time, Sam and Rosie started seeing a lot of very distinctive black butterflies with orange and white spots, and caught some for me. And, eventually after many attempts I managed to get a few decent pictures of one (I think I’ve mentioned before what uncooperative photographic subjects most butterflies are).

This is definitely a Baltimore Checkerspot. The thing is, we don’t recall ever seeing these butterflies around before this year, but this time they were all over the place. We saw more of these than we did of Monarchs (although, granted, the monarch population was down this year). I think the checkerspots may have just recently moved into the area. Or, they may be just prone to population explosions from time to time.

So anyway, these are the State Insect of Maryland. They overwinter as caterpillars, which is why I found the ready-to-pupate caterpillar in May. Their normal native food plant is something called “turtlehead”, which I don’t believe I’ve ever seen around here. Although, the USDA says we are within the range of this plant, so maybe it is around and I just don’t remember it. However, the Baltimore Checkerspots have evidently also taken a liking to English Plantain, which is a very common invasive plant in our lawn, and so they are very likey to have been eating that. So for my next post, I guess plantain would be a good choice.

5 Responses
  1. Carole permalink
    September 7, 2016

    You plantain article isn’t opening.
    You are such a good observer of what lives in your area I hesitate to suggest, but could your mowing schedule have anything to do with the lack of checkerspots in the past. If they are overwintering, are the plants they may be overwintering on making it through the winter?

  2. September 8, 2016

    I hadn’t actually intended the Plantain article to go live until Saturday, but I accidentally hit “publish” instead of “schedule”. It was only online for a few seconds, but it looks like that was long enough for all the RSS feeds to pick it up. So, I went ahead and posted it early, it should be visible now.

    I don’t think our mowing schedule would have much of an effect, since we own 9 acres of land and probably mow only about 1 acre (and usually don’t even mow that once the growth rate of the grass slows down in the fall). These caterpillars appear to have similar overwintering habits to wooly bear caterpillars, and we have lots and lots of those.

  3. September 8, 2016

    Is this first time you’ve hatched out a wasp? What percentage of caterpillars do you think are already doomed when they build their chrysalis?

  4. September 9, 2016

    Tim: This is the third time I’ve gotten wasps (the previous times there were numerous little wasps instead of one big one), and at least three other occasions I’ve gotten parasitic flies. I’d say that somewhere around 10% or so of the caterpillars that I try to rear are infested with something that will come out of their cocoon or chrysalis instead. It’s a hard world for insect larvae. There has only occasionally been any external indication of what was going to happen, though, and it has almost always been a surprise.

  5. Mark Sturtevant permalink
    October 7, 2016

    I keep my eye out for checkerspots, but so far have not seen one. They are high on my list. I have a buggy friend who says he sees a few every year. Odd how some critters are seen by some, never seen by others.

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