And so it begins, again.

I've had a horseshoe crab itch for many years — not some weird disease (thankfully), but a keen interest that's waxed and waned but never left me.

It started when I was in graduate school in 2003 and landed a spot on a horseshoe crab (Limulus polyphemus) spawning survey at Taunton Bay on the coast of Maine. My mom found out about the spawning survey from a local conservation group, Friends of Taunton Bay, and heard they were looking for volunteers.

I found a way to spend the late spring and summer that year near the bay, living in my parents’ house in between their bed and breakfast guests, waiting tables at a nearby restaurant to support my horseshoe crab habit. I told my manager that my availability for shifts would change with the tide cycles, and she looked at me for a few long moments to see if I was kidding.  

That was a long time ago. Since then, through many life changes, losses and joys, and professional twists and turns, I've checked in with horseshoe crabs from time to time. To see how they’re doing, what we are learning about them, and from them. Reconnecting with old friends, and finding my curiosity kindled all over again.

I am fascinated by our human relationship with these “living fossils” and their ancestors, who have inhabited coastal areas on Earth for around 450 million years but look very similar today to their ancient forms. They have weathered not just one but several mass extinction events that wiped out many other species, including the one 65 million years ago that ended the age of dinosaurs. They have witnessed continents drifting apart and crashing together, coastlines receding and advancing, and dramatic changes in the chemistry of the oceans.

Horseshoe crabs are clearly resilient, and humans have tested that resilience time and again. We have harvested them by the millions, for fertilizer in the 19^th and early 20^th centuries and more recently for use as bait to fish for eel and conch. Since the 1970s, we have harvested their blood and isolated a compound from it to test medicines, vaccines, and medical devices for contamination by bacterial toxins that can harm us. I don't think it's an exaggeration to say that most if not all of us owe a debt to these ancient arthropods.

Now horseshoe crabs face complex, compounded threats and changes that are happening at a rapid pace, many of which are fueled by our actions and inactions. Over-harvesting, loss of habitat, warming seas, and other effects of climate change, to name a few.

Yet there are also bright spots. More and more people are falling in love with Limulus, and working to protect them. In May 2025, the U.S. Pharmacopeia formally approved a synthetic alternative to LAL, the compound from horseshoe crab blood that’s protected us from illness and even death for decades. In late 2025, New York Gov. Kathy Hochul signed the Horseshoe Crab Protection Act into law, banning the commercial harvest of horseshoe crabs by 2029. These conservation successes are built on years of dedicated, persistent organizing and advocacy, including citizen action.

There’s reason for despair, heartbreak, joy, and hope. In these pages we’ll explore it all, starting with horseshoe crabs in Maine, where I live and where horseshoe crabs teeter on the very northern end of their range. I hope you’ll join me in these Travels with Limulus.