I have some questions about the Druid wildshape feature.
1) If a druid wildshapes into a snake or a poisonous frog or any other kind of poisonous or venomous animal could you harvest the poison or does it cease to exist once the druid resumes form.
2) If you cannot harvest the poison what about attacks with ongoing effects of the poison such as the Giant Centipede or Giant Spider bite.
3) Can a druid choose the gender of the animal it changes in to or is it the same gender as the druid.
4) If a druid wildshapes into an animal and is then shaved does he lose hair in his normal form or does the hair just cease to exist once he turns back.
As far as I can tell there is nothing in the PHB about this so I assume it is up to DM discretion but I was wondering if there were any rulings from past editions that might be applicable or other rules about shapeshifting.
That depends on if you allow harvesting poison of those creatures, in general. Already, there are no rules on gathering poison from creatures, so these are purely up to the DM on a case-by-case-basis. And might be one of the reasons why I don't allow harvesting/milking such creatures...
As for #2, well, the poison is already in their veins, I don't see why it'd suddenly stop...
3 and 4 are also "DM on a case-by-case basis" and I'd certainly allow the choice of gender AND sex (don't forget there's a difference 
)
#4 could be comical, so I may allow it. Otherwise it would either remain afterwards, or simply disappear when reverting. I think if I ruled that it "remained afterwards" then I'd probably have that hair come from SOMEwhere, probably the druid's body (if applicable)
(and don't pay TOO much attention to past additions, especially with poison harvesting. Personally, I say wait for the DMG for potential rules on that)