Parasites live off – and often on – other animals. But what live on the parasites?

Hectonichus [CC BY-SA 3.0], via Wikimedia Commons
Let’s begin with some more flea poetry. Obviously, the natural place to start.

Last time I wrote about fleas in poetry I held one back because it relates well to today’s topic. In 1733, Jonathan Swift wrote the following lines:

So nat’ralists observe, a flea
Hath smaller fleas that on him prey;
And these have smaller fleas to bite ’em.
And so proceeds ad infinitum.

(An aside: I assume that “flea” and “prey” rhymed in Swift’s accent and it’s not just a purposeful slant rhyme. Any historical linguists out there care to weigh in?)

This idea, that parasites have smaller parasites, actually exists in nature. Take, for example, the white butterfly Pieris rapae. A tiny wasp called Cotesia glomerata lays its eggs in the white butterfly’s caterpillar. The eggs hatch and the parasites eat the poor caterpillar from the inside out. There’s no justice in the natural world.

Or is there? Another, even tinier wasp called Lysibia nana lays its eggs in the parasite’s larva. It’s a hyperparasite, a wasp in a wasp in a caterpillar. Reworking Swift’s poem:

So nat’ralists see, a butterfly
Hath smaller wasps that on him prey;
And these have smaller wasps to bite ’em.
And so proceeds ad infinitum.

(If Swift is allowed to rhyme “flea” and “prey” then I’m allowed to rhyme “fly” and “prey.” Don’t @ me.)

The Wikipedia article on hyperparasitism suggests that in some cases this can go five layers deep (parasites on parasites on parasites on parasites) but I cannot find good evidence of that.

[End note: this is one of the topics I promised to write about. More to follow.]

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