danger, will robinson!

In the comments that followed yesterday’s update on the Monarch caterpillars, I once again made mention of predatory Stink Bugs. I guess a post about them is long overdue, so today’s the day.

Stink Bugs (Family Pentatomidae), belong to the Order Hemiptera, commonly referred to as the True Bugs. Hemiptera means “half wings” and describes the often thicker forewings that cover the membranous hind flying wings. They also have mouthparts which are beak-like, for stabbing into and sucking juices or fluids from either plants or prey. Some feed on plants, while others are predatory and feed mainly on other insects. The common name “Stink Bug” refers to a stinky fluid which these insects can discharge. I have a photo somewhere in my gadzillions of insect photos, of a droplet of the fluid falling from a stinkbug that I was photographing. Unfortunately, it would take awhile to find it, so you’ll have to either imagine it or go out and find a Stink Bug to see for yourself.

While a large number of Stink Bugs feed on plant juices, there are quite a few species that feed on the body fluids of insect prey. Most predatory Stink Bugs that I’ve photographed are species of Podisus (Soldier Bugs) which tend to have very sharp projections from the thorax (pointy shoulders), as in the above photo. Or they are species of Brochymena, which are gray, pebbly surfaced, and well camouflaged to resemble the tree bark where they commonly hunt. I’ll post some photos of Brochymenas sometime in the next few weeks when they begin to be frequently seen around the farm.

I often encounter predatory Stink Bugs while searching for Monarch caterpillars. I’ve posted a thumbnail photo of one on the left (just click on it for a larger view if you don’t mind a typically ghastly sight from the not-so-pretty face of the insect world). With this summer’s focus on the Monarchs, I’ve discovered just how rare a thing it is for the caterpillars to evade predatory Stink Bugs and similar “hunters” such as the Assassin Bug. If I find even one of either of these insects on a Milkweed plant, it’s very rare for me to find any living Monarch larvae on that plant or any of those within several feet. I believe they are very efficient hunters, especially the Stink Bugs, which seem to be constantly on the prowl.

While not much remains of small caterpillars killed by Stink Bugs, it’s not uncommon to find the blackened body of a larger caterpillar draped among the Milkweed leaves (again, just click for a larger view if you don’t mind such sights). Apparently, larger caterpillars are no match for the stalking Stink Bug.

Predatory insects such as Assassin, Ambush and Stink Bugs are considered to be among the “beneficial” insects — those that will hunt for crop-destroying prey — but it must be remembered that they don’t restrict their hunting to the less-desirable prey. Most will hunt down and feed on just about anything they can capture. For example, Ambush Bugs (Phymata) capture many pollinating insects such as Honey and Bumblebees. Apparently, they aren’t much liked by beekeepers. Similarly, a Stink Bug may be a big help chasing down Cabbage worms in the vegetable garden, but seems more like a nasty marauder when it’s hunting for Monarch caterpillars in the Milkweed patch.

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13 Responses to “danger, will robinson!”

  1. Mark Paris Says:

    I wonder what an alien would think of our own behavior. Beneficial, or harmful?

  2. burning silo Says:

    Mark – I think any alien would probably be terrified by human behavior, especially if they were to monitor our television news broadcasts for awhile. They would probably be turning their space ships around and heading elsewhere.

  3. Lynne Says:

    You’ve got the makings of a really scary sci-fi movie!

  4. burning silo Says:

    Lynne – One thing about insects. I’m very glad they don’t grow any bigger. (-:

  5. robin andrea Says:

    When I read about Stink Bugs, Assassins, Ambush, and Soldier Bugs, I realize that some critters have names that just suit them perfectly. Also, a nice reminder that for most creatures life is about food, territory and reproduction.

  6. Wayne Says:

    Ha! Didn’t the “brain bug” in “Starship Troopers” do this?

    Great photos of a ghastly sight, Bev. You can almost see the contents being transferred from victim to perp. I hadn’t really thought of stink bugs as being predatory before. It’s interesting how the mouthparts of the insects of the order can be used for sucking out the insides of plants OR animals.

  7. burning silo Says:

    Robin – Yes, aren’t those names well suited? As I go about on my insect walks, I often think that insects reduce the concept of survival to the most basic level — eat, grow, reproduce, die. The life cycle is so accelerated and the reality so apparent. It seems to me that there’s something to be learned from it. Comparatively, we humans have such long lives and can control so many aspects of our lives. We should be celebrating that difference — enjoying the benefits of all that we can grow, create, and think — but instead, so many seem so hell-bent on causing misery and destruction. We should be willing to share more, and yet, when the old hoarding instinct kicks into gear, it causes many to go nuts trying to accumulate a bigger stash than everyone else. Sometimes, it all seems so perverse. Watching insects seems so less complicated.

    Wayne – I’m not sure about the movie but Don would know. I’ll have to ask him about it.
    Until a couple of years ago, I never realized that there were quite a number of predatory Stink Bug species — I just assumed all were plant feeders. As you’ve mentioned, the mouthparts seem adapted to be used for feeding on the fluids of either plants or animals, so it’s usually difficult to figure out who eats what. Further, even now, I sometimes find Stink Bugs that look to me as though they should be plant-feeders (no exaggerated thorax spines, etc…), but are feeding on another insect. It would be interesting to know more about their taxonomy and how the plant feeders differ from the predator species. So far, I haven’t found a really good book on them, but I keep looking. With all of the interest on insects these day, I’m sure there must be something out there, or will be before long. One thing I can say is that predatory Stink Bugs become much more conspicuous in late summer as they hunt for caterpillars. In early autumn, I often find them in the midst of killing Woolly Bear (Pyrrharctia isabella) caterpillars.

  8. Carel Says:

    I remember seeing a normally vegetarian Boxelder Bug (Boisea sp.) pierce my younger brother’s arm once: the only time I’ve seen one of these common bugs feed on live animal prey.

  9. burning silo Says:

    Carel – That’s pretty interesting. I’ve sometimes wondered if many of the Stink Bugs will feed on either plant or insect prey. I’ve frequently seen Ambush Bugs (Phymata) appear to be feeding on nectar from flowers, so I suspect that many of these bugs will feed on whatever happens to be readily available.

  10. Steve Says:

    I have read through your information on Stink Bugs and am wondering about their habits indoors. I live i southeastern PA and since last spring I have been finding the bugs around windows. I thought it was because of open windows. I closed the windows and the amount of bugs seemed to decrease but not go away. In early fall, they seemed to go away. Now it has been below freezing for over a week for the first time this winter and they seem to have reappeared. I have found several in my house again. Any thoughts?

  11. burning silo Says:

    Hi Steve – I’ve never had stink bugs come indoors, but that’s not to say they wouldn’t do so, especially in somewhat warmer climates than here in eastern Ontario. The only bug we see quite often in late autumn and sometimes in winter is this on — somewhat similar in appearance to a stink bug — it’s the Conifer Seed Bug (Leptoglossus occidentalis)
    They appear and wander around near the windows in late autumn, and I sometimes find them in the kitchen in winter (usually walking around near the sink).

  12. Amber Says:

    I have tons of these stink bugs indoors…I can take a large picture down and literally there are 10 or so…and within the curtains, I’ll find 4 or 5 of them per curtain. Any idea what the attraction is to these bugs to be indoors?

  13. bev Says:

    Amber – I have no idea. I don’t think I’ve ever found one indoors around here. As mentioned in my comment just above yours, I have found Conifer Seed Bugs in my house (see that comment for a link to a photo of one), and they behave much like what you’ve mentioned — although I’ve never had that many in the house at once — usually maybe a half dozen in the screened in sun porch and one or two that manage to get into the kitchen. I would think the stink bugs would prefer to be outdoors if they could find there way out there. Do you have any houseplants, or a plant that could have had eggs on it? Some stink bugs suck juices from plants as their food. I’m guessing that’s the kind that you might have. Some species of stink bugs prey on other insects, but I can’t imagine that that kind would find enough insects to feed on inside a house, so that kind seems unlikely.