I Speak for the Milkweed Tussock Moth!

I Speak for the Milkweed Tussock Moth!
Bug Bytes
Authors
Joe Boggs
Published on
July 19, 2016
I came across early instar milkweed tussock moth caterpillars (Euchaetes egle) feeding on their
namesake host yesterday and they reminded me of an e-mail message I received last year.
The message was from a well-meaning monarch butterfly (Danaus plexippus) enthusiast who
asked how they could control tussock caterpillars so they wouldn't compete with monarchs.
I was aghast. We celebrate the rejection of a monarchy each July 4!
It can't be denied that milkweed tussock moth caterpillars are ravenous feeders and serious
competitors to monarchs. All instars feed side-by-side in groups and a single colony can rapidly
consume entire leaves leaving only the veins. In fact, high populations can out-devour even the
most voracious monarch caterpillar. However, the tussock moths are also native insects; they
should enjoy the same natural born rights to milkweeds as monarchs. I support the colonies!
I'm also partial to the ugly duckling story played out as the tussock moth caterpillars develop.
Most pictures posted online show the colorful late instar caterpillars such as the one appearing
at the beginning of this report. The black and orange hairs punctuated by tufts of long white and
black hairs are responsible for the alternate common name of "milkweed tiger moth." Early
instar caterpillars represent an ugly duckling stage. The small, yellow-green caterpillars have no
discernable markings. With black head capsules and wispy white hairs, they have been
described as "non-descript;" an ignoble label.
The colorful late instar milkweed tussock moth caterpillars are actually advertising their chemical
defense strategy. Like monarch caterpillarsand many other milkweed-herbivorous insects
, the tussock moth caterpillars dodge predation by accumulating in their flesh the alkaloid toxins,
called cardiac glycosides (cardenolides), which are concentrated in the milkweed's sap.
As with other insects that feed on milkweeds, including monarchs, late instar tussock moth
caterpillars advertise their toxic character through splashy coloration; a twist to the old axiom
that "you are what you eat."
Of course, I support monarch recovery. However, we should embrace all native insects with
equal affection; I mean this figuratively since tussock moth caterpillars also have defensive hairs.
In summary, I quote Groucho Marx: "Those are my principles, and if you don't like them... well, I
have others."
Tags
Milkweed