regal eclosion again

[lday at iquest.net]

I got almost no response to my query about the environmental cues
that regal and imperial moth pupae use to know when to hatch.
One person suggested that even though they are many inches underground,
they still somehow receive light.  I can hardly believe this is
possible, but perhaps the pupa wriggles closer to the surface to
get light?  I have no idea.

If any of you know, or can suggest relevant reading material, I
would appreciate it.

Thanks,

:-)
Liz Day

LDAY at iquest.net 
Indianapolis, Indiana, central USA, 40 N latitude, zone 5.
Home of "Fred", the oldest living regal moth pupa.
http://www.iquest.net/~lday