Fishing Spider

Physical Characteristics

Fishing spiders (Dolomedes spp.) are large, semi-aquatic spiders known for their ability to walk on water and hunt aquatic prey.

Body:
They have a robust, elongated body with long legs adapted for movement on both land and water. The cephalothorax is broad, and the abdomen is oval-shaped with subtle patterns.

Coloration:
Fishing spiders are typically gray, brown, or tan with mottled or striped patterns that provide camouflage against tree bark, rocks, or water surfaces. Some species show lighter bands along the legs and a pale stripe running lengthwise down the body.

Eyes:
They have eight eyes arranged in two rows, providing excellent vision for detecting movement above and below water.

Legs:
Their long, powerful legs are covered with hydrophobic hairs, allowing them to skate across water surfaces or submerge briefly while hunting.

Size:
Adults typically measure 0.6–1 in (15–25 mm) in body length, with a leg span reaching 3–4 in (7.5–10 cm). Some species, like the dark fishing spider (Dolomedes tenebrosus), can have a leg span of over 4 in (11 cm).

Weight:
They are lightweight, usually under 2 g, which allows them to float on water without breaking the surface tension.

The fishing spider’s camouflaged body, hydrophobic legs, and large size make it one of the most distinctive and impressive semi-aquatic spiders in North America and beyond.

Reproduction

Fishing spiders have fascinating reproductive behaviors, often involving complex courtship and maternal care.

Mating and Courtship:
Males approach females cautiously, as they risk being mistaken for prey and eaten (sexual cannibalism). Courtship involves leg-tapping, vibrations, or other signals to calm the female before mating.

Copulation:
The male transfers sperm using specialized structures called pedipalps. In some species, males sacrifice themselves after mating, increasing the chances of the female using their sperm—a strategy known as “self-sacrificial mating.”

Egg Sac Production:
After mating, the female spins a large egg sac, often containing hundreds of eggs. She carries the sac in her jaws or attached to her spinnerets, protecting it as it develops.

Hatching:
When the eggs are ready to hatch, the female secures the sac to vegetation and guards it. Spiderlings emerge after a few weeks, dispersing by ballooning (riding air currents on silk threads) or crawling away.

Parental Care:
Females display maternal protection, guarding egg sacs and young until they disperse, which increases survival rates.

The fishing spider’s reproductive cycle—marked by risky male courtship, potential cannibalism, and strong maternal care—illustrates both the dangers and dedication of their life history.

Lifespan

Eating Habits

Uniqueness

Fishing spiders are remarkable arachnids, combining traits of both terrestrial hunters and aquatic specialists.

Water-Walking Ability:
Their hydrophobic leg hairs allow them to walk on water surfaces, a rare adaptation among spiders.

Underwater Hunting:
They can dive below the surface, using air trapped around their bodies like a scuba tank to breathe while pursuing prey.

Large Prey Capture:
Unlike most spiders, they can overpower and consume small fish, tadpoles, and aquatic insects much larger than themselves.

Maternal Care:
Females guard egg sacs and young spiderlings until they disperse, showing unusually high levels of parental protection.

Widespread Distribution:
Fishing spiders are found on every continent except Antarctica, thriving in ponds, streams, lakeshores, and marshes.

The fishing spider’s combination of water-walking, diving, and fish-hunting abilities makes it one of the most unique and versatile spider species in the world.