Re: Why do some butterflies bleed when they hatch from cocoons?

Actually, butterflies do not bleed when they emerge from their chrysalis, 
but release stored up waste products, which are often reddish like blood  
(with some few exceptions, insects lack red blood).  In Medieval times this 
was sometimes so prevalent as to be known as a rain of blood and was seen 
as a portent of some disastrous event.

References:

Cowan, F.  1865. Curious facts in the history of insects; including spiders 
and scorpions.  J. B. Lippincott & Co., Philadelphia.

This is a rather ancient text and almost totally unavailable (I just happen 
to have a copy).   There should be an explanation in more modern books, but 
I have not been able to locate one- probably in insect physiology texts.