I should know better.

In hot pursuit of a butterfly, I came around a bush and WHOOSH! I was immediately enveloped in bright yellow and pumpkin orange confetti. I’d stepped into the middle of a puddle party.

Puddle parties are social gatherings for butterflies. Dozens of butterflies—almost exclusively male and often young—will congregate in a single spot to sip from mud, a pile of excrement, the blood of fresh roadkill (I’ll spare you the visuals for that one), or even turtle tears (No, seriously. Check it out!).

The butterflies are searching for sodium, an ingredient that’s typically pretty scarce in a nectar-feeders diet, but critical for egg production.

The sodium-sipping males pass on their salty nuptial gift to the females during mating. Studies have shown that female butterflies that receive sodium from their male partner have larger eggs which produce more fit offspring.

But why is sodium-sipping a social event? Why not just go find your own puddle? Or bloody rodent. Or whatever?

As passing on sodium to your mate gives you a distinct evolutionary advantage, so does hanging out with the guys. There are benefits to participating in a puddle party.

Benefit 1: It’s easier to find the “good stuff” if you just follow the crowd. Male butterflies use visual cues to recognize brethren of the same (or similar) species. Once they see a gathering (a sure indication that someone’s found a good puddle) they’ll join in, swelling the ranks of the party.

Benefit 2: You’re less of a target. Puddle parties typically take place on the ground where the butterflies are more vulnerable to predators such as lizards. If you’re by yourself, you’re easy pickings. In a crowd though, there are a lot more eyes to watch for movement and you become “one of many” when your puddle party explodes into flight to avoid a predator (or an oblivious photographer).

Benefit 3: If a little advertising is good, then a whole lot of advertising is even better. Many butterflies have bright colors that warn “I don’t taste good, so save us both a lot of hassle, and don’t even try to eat me.” Gathered together in a puddle party, the message becomes a bit stronger: “WE DON’T TASTE GOOD, SO SAVE US BOTH A LOT OF HASSLE, AND DON’T EVEN TRY TO EAT US.” And if you try, we’re all going to fly away in a huge WHOOSH and you won’t be able to focus on a single one of us anyway. Ha!

Not all butterfly species participate in puddle parties. In my experience the most social of the butterflies appear to be swallowtails, blues, and sulphurs. Blues and sulphurs have grand mixed-species parties with marine blues hanging out with Reakirt’s blues or Sleepy Oranges mixing freely with Cloudless Sulphurs.

But swallowtails seem to be more aloof. Two-tailed swallowtails, those yellow and black beauties that soar high overhead, prefer to gather with others of their own species. Pipevine swallowtails may not be quite as picky and have been known to crash another swallowtails party.

It’s easy to host a puddle party in your yard if you have a butterfly-friendly garden (see my story on Butterfly Gardening for more information on that subject!). Choose a bare patch of dirt or sand, pour some salty water over it, and wait for the party to begin. It helps if your puddle stays damp for awhile, so you might want to put the sand or dirt into a shallow dish (such as a terracotta plant saucer) and keep adding salty fluids as it dries out.

Butterflies are fascinating creatures that do a lot more than just flit from flower to flower. While we know a lot about butterfly taxonomy, there’s still much to learn about butterfly behavior. So grab your binoculars, settle in, and just watch. Who knows what you’ll discover!