monarch caterpillars

Martha Rosett Lutz lutzrun at
Fri Sep 21 08:27:38 EDT 2001

NapaPenny wrote:

"How do these tachinid larvae do this - during catepillar stage.  Since
writing last night 1 has formed the J shape and the others are moving
around but not eating."

If the larva is parasitized with tachinids, it will usually be smaller than
is typical for monarch larvae, but this may be hard to judge unless you
have many others for comparison.  After the parasitized larva hangs in its
J, it will straighten out, become limp, and slender white strands will
descend from its body; these appear to be the exit tubes for the maggots.
(Can someone else comment on this?  I've never actually seen them exiting,
but as soon as I see the strands, I see the maggots on the floor of the
cage.)  The maggots pupate, and soon afterwards emerge as adult flies.
There can be several maggots per monarch larva.  I have had one case of a
larva that did pupate in spite of being parasitized, but after the maggots
exited from the chrysalis, it turned from green to brown and died (caved in
on itself).

In Stride,
Martha Rosett Lutz


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