Yes, it also works on Brown Hairstreak larvae. Doesn't work for eggs. Definitely wear UV protective glasses as they protect your eyes and make finding the larvae even easier.

This is fluoresence, not reflection. The caterpillar absorbs the UV and re-emits something in our visible spectrum. So in theory, it may function as a defence against predatory birds that can see in the UV spectrum.

Huge congrats Will! Fantastic news!

Certainly is.. the ants seem to completely avoid the adults

The adults often lay these amazing eggs amongst or near aphids and ants, to save the caterpillar time in finding its first meal. What an astonishing life-history strategy!

Unfortunately this doesn't work every time!

They have a really cool behaviour where they use a specialised organ (osmeterium) for defending themselves against predators or pests. They arch backwards and extend the osmeterium to deter the pest.