Waiting patiently

Last fall a female orb weaver spider (Argiope aurantia) left a brown papery egg sac on the ceiling of our carport, thus completing her life cycle. The life cycle of an orb weaver is an interesting one so lets look at it from the beginning: we will start with the egg sac.

Each oblong sac contains 300 to 1400 eggs. The eggs of this species hatch in the late fall, but the hatchling spiders become dormant and do not leave the egg sac until the following spring. The overwintering egg case will help protect the spiderlings from predation. Some egg cases become damaged by birds, and some species of wasps and flies will also lay their eggs in these cases. In fact, one study found that in addition to the orb weaver, nineteen species of insects and eleven species of spiders all emerged from one orb weaver egg case!

In Spring the spiderlings emerge and look just like small adult spiders. The females grow to be much larger than the males. Like all spiders, orb weavers are carnivorous. They spin an orb web to capture small flying insects such as aphids, flies, bees, wasps, and grasshoppers. A female can take prey up to up to 200% of her own size. These spiders are active both day and night, attacking insects that are trapped in its web which can be up to two feet across. The female orb weaver hangs, head down, in the center of her web while waiting for prey. Often, she holds her legs together in pairs so that it looks like an X. The entire web is usually eaten and then rebuilt each night, often in the same place.

Once the male orb weaver matures, they leave their own webs and wander in search of females. When they find one, they will wait around the edge of her web, sometimes building small webs of their own, waiting to mate with the female. After mating, the female produces 1-3 brown, papery egg sacs. She will attach her egg sacs to one side of her web, close to her resting position at the center. She then watches over her eggs as long as she can, but she will die in the first hard frost, if not before.

This brings us back to the brown, oblong egg case in our carport, which we are patiently awaiting the emergence of the orb weaver spiderlings (and maybe others?).