Cannibalistic Monarchs / part II

Martha V. Lutz & Charles T. Lutz lutzrun at
Mon Aug 14 18:57:40 EDT 2000

Hi . . . me again.  My original note got this response:

///> Can anyone confirm (or refute) for me that Monarch larvae will eat
> conspecific eggs?  A few years ago while raising Monarchs I lost an egg.  I
> thought I had miscounted eggs, or perhaps misplaced one, or maybe the kids
> took it out and didn't put it back.  I thought about that disappearing egg
> today--when it happened again.

I know whereof you speak.

There a number of other possibilities.  Lacewings (probably either adults or
immatures) and coccinelids (ladybugs, also probably either adults or immatures)
come to mind right off the bat.  I had a couple hours-old hatchling gulf
fritillary caterpillars (and one less than an hour old) a couple years ago and
lost both them an some eggs on host plant (pssion vine foliage).  On checking
them the afternoon after I had captured them, I found one nice fat lacewing
larva and no caterpillars or eggs.  I was not a happy camper.

Pierre A Plauzoles
sphinxangelorum at


It's a great hypothesis!  But I should have mentioned (sorry I left this
out) that the Monarchs were the only living things in the cage, so I can
rule out predation other than by the one larva on the same leaf.  I have,
in the past, lost various Saturniid larvae to spiders that rode in on the
twigs I used to feed the caterpillars, but with these Monarchs I was using
single leaves, and had looked them over pretty carefully first.

Another possibility I thought of was that the egg was sterile and simply
collapsed to the point of invisibility (although I did look for
it--unsuccessfully--under a low-power magnifying glass).  Today I swiped
the egg from a newly-hatched Monarch and took a good look at it . . . there
was nothing I saw that looked like that eggshell after egg #1 vanished.

I hesitate to simply conclude that there is cannibalism among Monarch
larvae, but I can't rule it out at this point, either!

Does anyone have any more information on this?

Since Saturniids are not cannibalistic (not mine, anyway), it does raise
some curious evolutionary ideas about Monarchs.  There are some interesting
possibilities concerning the selection pressures that would produce this


In Stride,

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