The boys & I just returned from a big adventure, we camped at Thomas Point Beach in Brunswick to witness the annual horseshoe crab migration. Every year, right around the full moon in May and June, horseshoe crabs migrate to protected beaches within bays and coves to spawn. This was such an amazing and memorable experience for all of us, I can't believe that the horseshoe crabs have been doing this for over 350 million years and we only just discovered that they are spawning here in Maine.

Some of these crabs are so old, like the male in the above picture, that they've taken on passengers. We saw many crabs with barnacles, shells, snails and big mussels on their backs.
The horseshoe crabs lay their eggs in the sand, either on the beach above the high tide line or in shallow waters. The crabs were everywhere, we saw thousands of them.
Though they look a little scary, the crabs are harmless to people. In fact, they are quite helpful to humans - anyone in the U.S. who has ever received an injectible medication has benefited from horseshoe crab blood, which is used by pharmaceutical and medical device companies to ensure that their products are free of bacterial contamination.
Levi & I especially loved the juveniles. These little guys live in the intertidal flats for up to nine years before they reach sexual maturity and begin this migration to the beach themselves. During this time they will molt up to 17 times.
When you stand in the water with the horseshoe crabs, they bump you repeatedly and crawl over your feet, which can be a little startling the first few times in happens. One of them voluntarily wandered into the moat around Si & Levi's sandcastle, which greatly pleased the boys. After that, many more went into the moat, but not of their own free will.
If you'd like to see this spectacular event for yourself, the horseshoe crabs will head for the beaches again next month around the full moon on June 26th. Delaware Bay is the largest spawning ground in the world for horseshoes, but if you are in Maine, head to Thomas Point Beach, you won't be disappointed!
Floating around with the horseshoes were hundreds of beautiful (and harmless) moon jellyfish.
If you'd like to learn more about these interesting creatures, check out this episode of Nature on PBS.org. Silas put the horseshoes right up to his face and let them tickle him with their legs, just like the fisherman in this show.
By the way, if you do go to Brunswick, don't play with the toxic browntail moth caterpillars or you may end up with a very itchy rash, like Levi did when we first arrived at the campground (luckily it went away after some medicine, a shower & a change of clothes).
The view from our campsite.