frass expulsion

[gwang]

Hi,

> Maybe the second instars don't get parasitized?

This seems like an unlikely explanation.  When I collect monarchs in the
larval stage, I have often found that the bigger they are when I collect
them, the higher the probability that they have parasites.  This makes
sense if one thinks about it.  The parasites need a fairly large host to
ensure that its eggs have enough to eat.
As for the projectile frass thing, could it be that the caterpillars
simply want to get the frass of the leaves they're on?  Big caterpillars
would have no problem with this as their frass is heavy and drops
easily, where as small caterpillars' frass does not.  I have often
noticed with monarchs that the bigger the caterpillars, the easier it is
to clean their container as the frass falls away more easily.
Actually, I have never seen this projectile phenomenon you speak of. 
Just what kinds of distances are we talking about here?  A few
centimeters?

Peace,
Xi Wang

 
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