Re: What happens when a daddy long legs loses a leg? Does it grow back?

True daddy-long-legs are members of the arachnid order Opiliones (or 
Phalangida).  When immature and still molting, spiders (arachnid order 
Araneae) generally can regenerate their legs (although they may be 
smaller -depending on how many molts they have to go through to reach 
maturity).   Once they reach maturity after their last molt lost legs are 
not regenerated.  However, according to Barnes(1987)and apparently unlike 
spiders,  true daddy-long-legs cannot regenerate lost legs.

Reference:

Barnes, R. D. 1987. Invertebrate Zoology, 5th ed. Saunders College 
Publishing, Philadelphia.