Limulus polyphemus, Delaware Bay, DE, 2014
I didn't have much interest in the horseshoe crab before we spent a week on the beach in Delaware and were surrounded by them. Curiosity got the best of me, as it almost always does, and lucky for me that our cottage rental had several books on the local flora, fauna, and even covered the geology of the region.
Above are two female horseshoe crabs, dorsal and ventral views. The exposed pincers on the left specimen are what gives away the sex. When sexing a horseshoe crab you simply turn them over and and look at the first set of pincers. If they're pincer-like in appearance, then it's a female. If they look like tiny boxing gloves, then it's a male. The boxing glove-like appendage aids the male in mounting and holding on to the larger female.
While walking the beach we discovered many small, desiccated remains of horseshoe craps, and I brought a few home with me in a shoe box. I should've paid closer attention because all of the specimens I gathered were female. I'd based which ones to take on the condition of the remains, so that's my only excuse.
We're returning to the beach in Delaware this summer. With luck I'll find a good example of a dead male horseshoe crab that's in one piece.