One of our chairs on the dock has been turned into a nursery. A Ground Crab Spider has decided that a bright red colour makes a good setting for her babies to arrive. I am not sure if she is colour blind or if actually her babies will blend well with the colour when they hatch, but her white silk sheets certainly stand out for all to see!
This spider might be challenged in how it sees this nursery setting, but Crab spiders do have excellent eyesight. Their eyes are slightly different to most spiders. Spiders have eight eyes, but Crab spiders have two big front eyes.
Although Crab spiders extend their legs to the side like crabs, they do not walk sideways. Their front four legs are longer than their back four legs. Their long front legs are perfect for capturing and holding and grabbing their prey. The first pair of legs has sharp spines, which help hold their prey. Crab spiders are ambush spiders and they will patiently wait on in or around plants for unsuspecting insects to pass by. Their potent venom allows them to attack insects much larger than themselves and they will even take on wasps and bees. They have strong jaws and make small holes in the prey and vomit their digestive fluid into the prey’s body and then suck it out. They do not create webs to catch their prey, but they do use silk to make their egg sacs.
It was interesting to see how the spider was using her pedipalps as an extra pair of hands to make her egg sac. These look like little “legs” that are not used for walking. They are tactile organs used to manipulate food to the mouth and they also function as taste and smell organs. In males they are also used to transfer sperm to the female during mating.
I returned later and could not find any sight of mother, but the female does remain near the egg sacs to protect them, so we had better not get too close because they can bite. The bite is not dangerous to humans and most are not big enough to break the skin with their fangs, but I don’t fancy giving it the opportunity to try!