Trying to Understand Aphids

We have giant ragweed, Ambrosia trifida all over our place.  It’s a weed that grows where weeds grow.  A couple of smaller plants are growing along the driveway and they are covered with aphids.

There is a lot of cool stuff that happens with aphids, biologically speaking.  Aphids have an unusual strategy for survival.  They suck plant juices for food, and they cannot hide from predators.  Instead, they try to out-reproduce them.  Some attract ants which provide them some protection–the group that I saw did not have any ants, however.

I took a whole bunch of photographs, and tried to sort out what I was seeing.  Aphids have many generations per year, and those generations fluctuate between winged, sexually reproducing and egg-laying individuals to wingless, parthenogenetic females which give birth to live young.

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Here is such a female.  They pretty much stay in the same spot, sucking plant juices.  They are capable of crawling along the stem, but I only saw a couple of individuals do that.  They do jerk rapidly on occasion, ending up at about a 90 degree angle from where they started.

As you might expect, mixed in with the live aphids is a bunch of debris–shed exoskeletons from aphids that are growing, and the discarded exoskeletons of aphids that were prey to some creature or another.  On some parts of the plant there is a lot more debris than there are live aphids.

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This is a winged aphid that has some sort of deformation to its wing.  It seemed to be alive but I suspect it will not survive.

In addition to the debris of exoskeletons, there are “aphid mummies.”  There is a wasp that inserts its eggs into the living aphid, then the larva of the wasp eats the aphid from the inside out.  This is the shell of an aphid mummy, after the larva has eaten its way out.

Here is a link to a wasp emerging from an aphid mummy.

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Here is a tiny wasp on top of an aphid mummy.  But it did not emerge from the  mummy–in fact I observed it flying around.  I think this is a hyper-parasite–it lays its eggs in the body of the wasp larva that is living within the aphid.  But I don’t know that for sure.

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These charming fellows seem to be fly larva.  Once again, I can’t be sure, but I think they might be aphid midge larva.

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This is a brown lacewing nymph.  Below it you can see an aphid mummy.

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This colorful creature is the larvae of a syrphid fly.  It seems to be surrounded only by corpses.

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Here is a smaller syrphid fly larvae actively consuming an aphid.

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I don’t know which species of syrphid the larva represent, but these adult syrphid flies visited the ragweed and aphids quite often.

I would love to give the species names for all of the creatures I have shown, but it is next to impossible to make that determination from photographs, even for experts (which I am not).  I think I got the general story right, but feel free to correct me if you know better.

Aphids are strange creatures, and the things that feed on them are even stranger.

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About the roused bear

Nature photographer from central Iowa.
This entry was posted in Biological diversity, insects, Uncategorized and tagged , , , . Bookmark the permalink.

2 Responses to Trying to Understand Aphids

  1. Alan @ it's not work, it's gardening! says:

    Fascinating! Thanks for taking the time to photograph and post!

  2. theresagreen says:

    You see all this, a whole other world that escapes the notice of most of us and wonder why we are more fascinated by what may or may not be happening on other planets!

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