A Harlequin Romance: Coming to a Cabbage Patch Near You

A Harlequin romance is supposed to be predictable.  Pretty girl meets handsome, mysterious man and proceeds to engage in a sappy and steamy love affair.  A harlequin character is supposed to be a zany fool, a buffoon at whom you poke fun.  A harlequin pattern is bold, red and black diamonds.  How could I miss all this?

Of course I did notice the bold, red and black coloration.  It was an interesting insect, new to me, and so I let it alone.  I thought it beautiful.  As one should with new romances, I took it slowly.  Was it a predator of plants or bugs?  I kept meaning to look it up, but days went by.  I approached cautiously, admiring its stark, sleek coat of arms.  One morning I went in search of it for a picture and saw the answer to my question:  it was munching my cabbage!

The harlequin cabbage bug (Murgantia histrionica), not to be confused with the harlequin beetle (Acrocinus longimanus), is a black stinkbug with bright red, orange, or yellow coloration.  It is considered dangerous – to a cabbage plant that is – and it is described as an important pest.  It causes damage by sucking the sap out of plants, but what I saw appeared to be munching, not sucking.  I thought that perhaps the nymphs do the sucking damage.  I promptly removed all the eggs I could find. They are quite beautiful.  I’d not yet seen a nymph.  However, that does not mean I’d broken this romantic life cycle.  The new nymphs are basically the size of the eggs (see excellent photos at this website: http://entnemdept.ufl.edu/creatures/veg/leaf/harlequin_bug.htm) and therefore, easily missed.

A Harlequin cabbage bug adult and a cabbage white butterfly larva.
A harlequin cabbage bug adult and a cabbage white butterfly larva.

I already have holes in most of my cabbage plant leaves thanks to the cabbage white butterfly. I pick off some of the larvae since they are numerous, but otherwise I try to live with the chewed leaves.  They taste the same and most of my cabbage is slated for fermentation.  No one will see the holes once I chop the leaves into small pieces.  But I’ve seen what the gray squash bugs can do to a squash plant, and I don’t want to share my cabbage with the harlequin cabbage bug.  This means daily checking.

I later realized that the harlequin bug I thought was munching on a cabbage leaf must have just been sitting right where a cabbage white larva had feasted and that is why I thought it was munching.  I soon noticed not only holes all over my cabbage, but lots of juicy green frass, otherwise known as caterpillar poop.  I wonder – since I might lose my cabbage – if there is much nitrogen in caterpillar poop.  At least I could get some fertilizer in the soil for the next go around.  All romances need a little give and take.

Beginning cabbage head full of holes and frass, and lots of larvae hiding in the folds.
Beginning cabbage head full of holes and frass, and lots of larvae hiding in the folds.

The harlequin cabbage bug is a hemimetabolous insect.  This means it undergoes incomplete metamorphosis in its development.  It goes from egg to nymph to adult through gradual changes as opposed to having a pupa stage (think butterflies), which is called holometabolism, or complete metamorphosis.  Grasshoppers and dragonflies are examples of other insects with hemimetabolism.

Harlequin cabbage bugs require anywhere from 50 to 80 days to complete one generation of their life cycle.  In warmer climates this means plenty of time for some extra-amorous affairs.  They overwinter as adults, ready for love in the spring.  I had never seen this insect before.  I am in awe of how the adults found my particular cabbage patch.  How far did they travel?  Was it serendipitous that two harlequin bugs met on my lovely cabbage? I did have lovely cabbage a few weeks ago.  I rather think not, since I found many adults and, unwittingly left them to their romantic interludes a bit too long.

So what happened to my daily checking?  Well, there is always much to do in a garden, and then we went away for four days.  Then, of course, there is much to do when one returns.  Today I got to that checking.  It seems some cabbage will indeed be lost, unless I want to spend a lot of time removing caterpillar poop before making my sauerkraut.  I also found more Harlequin adults and more eggs, this time with larva.  This means the dangerous sucking behavior has barely begun.  My poor plants.  The good news is that my chickens like cabbage and broccoli leaves.  Leaves with eggs or larvae are even better, like nuts on your sundae.  And the best news is that not all of my cabbage and broccoli are affected.  Yet.

Harlequin cabbage bug eggs and nymphs.
Harlequin cabbage bug eggs and nymphs.

Bold coloration in nature is often a sign that an organism is toxic.  This adaptation then caused some species to evolve bold coloration even though they are not toxic – a tricky protective mechanism called mimicry.  The cabbage harlequin bug is not toxic and can safely be fed to the chickens.  Of course, non-toxic does not mean tasty, and when I presented the girls with a bowl full of cabbage butterfly larvae and a harlequin bug, all but the bug was devoured.  They didn’t even attempt to taste it.  Seems I was the only fool.  No more cabbage romances for me.

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