why caterpillars eat their eggshells

[Martha Rosett Lutz]

Roy Cheeseman wrote:

"Not being a biochemist, I do not wish to do more than relate what I have always
understood to be true, namely that the eggshells are very rich in protein
(dunno what sort) and are consumed in order that this valuable resource be not
wasted."

I would not be surprised if that is true for some species.  I suspect that
not all eggshells are created equal, though.  My Saturniids have relatively
sturdy-looking eggshells, but never eat them.  Monarchs have flimsy, almost
ethereal-looking eggshells, but seem always to eat them.  They will also
eat unhatched eggshells of sibs and 'plant-mates,' which could be
interpreted as either taking advantage of a protein/nutrient source,
elimination of competition, or both.  I'd bet that there are several
different factors at work selecting for eggshell consumption, and these
factors probably vary with species.

How's that for trying to cover all the possibilities?  But I don't like the
hypothesis of feeding on conspecifics stimulated by kairomones in their
bodies from teh plants they feed on.  This would argue for coprophagy, too,
and although I would not be too surprised to hear of a coprophagous lep
larva, none of the species I have ever reared have exhibited this behavior,
no matter what their food plant (i.e. with or without powerful secondary
chemistry).

I hope this note is coherent . . . we got up early this morning (5 a.m. for
me, after getting to bed around 11 or so) and drove 35 miles to race a 5K
in the rain.  Our family has SUCH FUN on weekends in early spring in Iowa .
. .

In Stride,
Martha Rosett Lutz



 
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