The Changeling wasp is large, a full foot long, with glittering transparent wings and a multicoloured body, and infamous for the effects of it's sting. A single sting given to a human or humanoid wasp just hurts. A lot. According to some who have suffered the misfortune of being stung, it feels like a red hot poker would if applied to the skin. But it's what happens if a second sting is given that has gained this wasp it's infamy; the human's body will change sex over a period of about fifteen minites or so, to the opposite gender. Women will become men with fully functioning sex organs, males will become genuine females, who can get pregnant and give birth. They normally pass out and wake not long after as their new gender. Since the vast majority of people (or elves, dwarves and other races) wish to stay the gender that they were born as, the first thing done when a new town or city is founded is that people in sting-proof armour destroy the nests of these unwanted wasps. In the case of deeply patriarchal (or, much more rarely,deeply matriarchal) societies, to be changed into the gender at the bottom of the heap is a disaster. Rulers are deposed or at least stripped of effective power;those lower in society lose some or indeed all of the rights they enjoyed. In fairer societies, they still have the burden of proving who they are.
These things do not prey on humans and humanoid races, they only sting them if threatened or attacked. Their normal prey is other large insects and spiders,which they sting to paralyse, then munch up themselves or feed to their fist sized grubs. They normaly build large nests with twelve to twenty-four grubs and six to twelve adult wasps per nest, with at least two adult wasps and sometimes more guarding the nest and grubs at any one time.The grubs themselves have no stings, although they can give a nasty bite if handled carelessly. Once killed and crushed into a pulp, they can be put into food or drink to change someone's gender. However, the adult wasps will defend the grubs with their lives. Three stings are enough to paralyse a human for hours, and four or more in a day will kill without quick medical aid.Once someone's gender has been changed, it cannot be changed in the same way again.
To Queen the King- In a country that sees women as very much second class citizens,some nobles have been plotting to bring down their paranoid king not by killing her, but by turning him into a woman who will no longer be able to legally rule over them. And guess who gets to trek out into the back of beyond,risk their lives and their genders getting the grubs, prepare the grubs and then smuggle the potion past the royal bodyguards and poison the royal food without getting caught? The PCs.
Make Me A Male- A noblewoman, fearing she will be married against her will and fed up at the way she is belittled for being female, wants the PCs to prepare the potion for her.
Make Me A Girl- A nobleman is transsexual and would much rather be female, and wants the PCs to prepare the potion for him.
For the Zoo- The owner of a zoo will pay the PCs well if they can capture two adult.Changeling wasps without killing or hurting them in the process. Not an easy thing to do.