The ONLY Spider I don't mind.

Horseshoe crabs are marine Arthropods. They belong to the family Limulidae and order Xiphosura or Xiphosurida. While they resemble a crab they are not a crustacean, they belong to the subphylum Chelicerata, which is a close relative to the arachnid family. Yes, the Spider family.

They are used primarily for bait and in fertilizer but there has been a major decline in their population as a consequence of habitat destruction.  They are so closely related to their ancestors that they are considered a living fossil.

Here's a tidbit of information you may not know,  horseshoe crabs do not have hemoglobin in their blood, they use hemocyanin to carry oxygen and because the hemocyanin carries copper, a horse crabs blood is blue.

Now, their blood contains amebocytes which play a similar role to white blood cells in defending against pathogens. The crabs are collected and sent to bio medical horseshoe crab collectors.

Back at the lab the tissue around the animals heart is pierced and up to 30 percent of it's blood is drained. The amebocytes makes Limulus Amebocyte Lysate which is used to detect bacterial endotoxins in medical applications. The LAL extracted from the blood, goes for up to $15,000 per quart.