Nursery web spiders (Pisaurina mira) are fascinating creatures that belong to the family Pisauridae. Found primarily in North America and Europe, these spiders are named for their unique maternal behavior of building a silk web, or nursery, to protect their egg sac and young spiderlings. If you’re curious about whether a spider you’ve encountered is a nursery web spider, here are three key ways to identify them:

1. Observe their size, shape, and coloration:

Nursery web spiders exhibit sexual dimorphism, which means that females and males differ in size and coloration. Adult females typically measure between 10-18 millimeters, while males are smaller at about 8-13 millimeters. They have elongated bodies with two distinct body parts: the cephalothorax (head) and abdomen.

The color of a nursery web spider can vary from light brown to dark gray or black. They have distinct bands on their legs that alternate in light and dark shades. Additionally, these spiders often have various patterns on their cephalothorax and abdomen, such as light chevrons or stripes.

2. Examine their habitat:

Nursery web spiders prefer damp environments near water sources such as streams, ponds, or lakes. You can also find them in moist woodlands or wet grasslands. These spiders do not spin webs for capturing prey but instead use their excellent hunting skills to actively ambush insects.

If you find a spider in this type of environment and it matches the physical description above, there is a higher likelihood that it is a nursery web spider.

3. Look for the characteristic nursery web:

One of the most distinctive features of these spiders is their silk nursery web that female spiders construct to protect their egg sac and hatchlings. The female will create a flat platform using silk on which she places her egg sac. She then adds a tent-like structure over the platform, creating a protective nursery for her offspring. The opening of the nursery will often face downward or towards another surface to block predators’ entry.

If you come across a spider guarding this type of protective silk structure containing an egg sac, it is most likely a nursery web spider.

By considering the physical characteristics, habitat, and unique behaviors of the nursery web spider, you can confidently identify these fascinating arachnids and appreciate their intriguing maternal habits.