Green Aphids

2009 September 27

S_ was given a vanilla bean orchid plant[1] a while ago, and it has been growing like crazy in a pot on the kitchen windowsill. Until, that is, she noticed that the growing tips were starting to die back. On closer investigation, she found that the tips of the plant were infested with these:

They are some type of basic green aphid[2], one of the very large family Aphididae. It took almost six months for them to put in an appearance, so I doubt that they were on the plant when we got it. They are probably a local species that got in through an open window.


A key feature for identifying aphids is the food plant that they are found on. This will probably not help us a whole lot in this case, because the vanilla bean orchid is most certainly not native to Michigan. I sincerely doubt that anyone has really done much study to find out which of the local aphid species is prone to develop a taste for these plants. And, since there are an estimated 80 species of aphids in the US that are pests of ornamental plants (out of at least 1351 species in North America), I doubt I’m going to get any more detailed identification than this.

I can be sure that they are aphids (and not some other sort of plant-sucking insect, of which there are many), because they have the characteristic body shape, the typical long, spindly legs, and the “cornicles”, which are a pair of elongated nozzles that stick out of the topside of the abdomen:


Aphids use the cornicles for defense from predators. First, when an aphid gets attacked, it will use them to give off pheromones that alert the surrounding aphids of the danger. The liquid that they secrete with the pheromones also is sticky, and appears to gum up the mouthparts of the predator. Aphids also give off “honeydew” when they feed, a sugary liquid that ants like. There are several species of ant that will tend aphids so that they can lick off the honeydew, and the ants will then defend aphids from predators like lady beetles and lacewing larvae.


The big defense of aphids against predators, though, is their absolutely astonishing reproduction rate. They simply reproduce so very, very fast that none of their predators can really keep up. During the growing season, the female aphids reproduce parthenogenically, giving birth to live young as fast as they can. In fact, they are reportedly born pregnant, so they can start reproducing right away, often within only a few days after being born themselves.

Of course, up in places like Michigan that have cold winters, they can’t really keep this up year-round. They have to have a form that can overwinter, and their plump, juicy bodies don’t really take freezing very well. So, what most species of aphids do in the fall is produce a final generation, both male and female, that have wings. This winged form then breeds and lays eggs, which overwinter. Then in the spring, they hatch out a new generation of winged aphids that fly off and find a host plant. Once they do, they settle down and start eating, and next thing you know, they are popping out the new aphids like popcorn until the host plant is absolutely covered with aphids.

[1] I had always thought that vanilla beans were, well, beans, but it turns out they are not. They are actually a type of orchid that grows as a vine. Vanilla plantations consist of not just vanilla vines, but also trees that provide a scaffolding for the vanilla to climb up on.

[2] An old Far Side cartoon: A man has discovered his wife, bound and gagged outside under some bushes. He ungags her, and she cries, “Aphids! Aphids, Henry! There are aphids in the garden!”

4 Responses
  1. Sandra H permalink
    September 27, 2009

    Can these things survive the winter indoor? Am I doomed once I get them inside?

  2. September 27, 2009

    From a predator’s point of view, these things look like pure food. A big, bulbous body, probably loaded with easily digestible sugars and proteins and almost no unwanted body parts.

    I love the bit about the reproduction rate. Way cool. A link is on the way.

  3. September 28, 2009

    Some aphids can survive indoors year-round, particularly certain species that have adapted to greenhouses. It sounds like the aphids go into overwintering mode when the summer host plant starts preparing to go dormant, which isn’t going to happen in houseplants. The best bet is just to go through periodically and either squash or wash off the aphids.

    And yes, they are pretty much pure food. If you think of them as cattle domesticated by ants, that isn’t too far off, at least for a lot of species. It might be amusing to breed a plant that can tolerate large aphid populations, and an aphid big enough to make a noticeable snack for a person, and start raising aphids for food.

  4. September 29, 2009

    They might make a great ice cream topping!

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