frass expulsion

[Liz Day]

 >Since the original question dealt with projectile frass in 1st instar
 >Monarchs (if I remember correctly) could it have something to do with the
 >accumulation of toxins?  It seems to me that the first instars would be at
 >greater peril from predators since they have not yet accumulated the
 >quantities of milkweed toxin that later instars have.  Has anyone any
 >information regarding the relative toxicity of various instars? comparative
 >acceptability to predators of various instars?

I don't know about the monarchs.  The only species I've observed doing this 
(a sulfur butterfly and a notodontid moth), in both cases the larvae shot 
their frass through the whole period from hatching to pupating.   I don't 
think either species is ever toxic (??) so perhaps the monarch has a 
different situation.

Liz


 
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