Fishing spiders, belonging to the genus Dolomedes, are a captivating group of arachnids often found near aquatic environments. These spiders are known for their unique hunting abilities on water surfaces. Their striking size sets them apart from many common spiders.
The True Scale of Fishing Spiders
Fishing spiders grow to impressive sizes, often exceeding what many people expect from a spider. When considering their size, it is important to differentiate between body length and leg span. Body length refers to the measurement of the cephalothorax and abdomen, while leg span includes the full reach of their extended legs.
Female fishing spiders are typically larger than males. Their body length can range from approximately 0.27 inches (7 mm) to over 1 inch (26 mm). However, their leg span is where they truly become noticeable, often reaching between 2 to 4 inches (5 to 10 cm) in diameter.
Some species, such as the Dark Fishing Spider (Dolomedes tenebrosus), can have a leg span exceeding 3 inches (7.5 cm), with some reports indicating up to 4 inches (10 cm) for large females. This wide leg span allows them to effectively distribute their weight and move across water surfaces. For instance, the Six-spotted Fishing Spider (Dolomedes triton) can be around 2.4 inches (60 mm) including legs for females.
What Influences Their Size
Several factors contribute to a fishing spider’s ultimate size. Different species within the Dolomedes genus naturally possess varying maximum sizes. For example, Dolomedes tenebrosus females are among the larger species, while others might be comparatively smaller.
Sexual dimorphism plays a significant role, with females consistently being larger than males. In some species, such as Dolomedes tenebrosus, females can be twice the size of males in body length and weigh significantly more.
Diet and the availability of food are also influential. A consistent and ample supply of prey, such as insects, small fish, and tadpoles, allows fishing spiders to grow larger. These spiders are opportunistic hunters, and diverse prey contributes to their growth.
Suitable habitats with stable conditions provide an environment conducive to larger individuals. Fishing spiders thrive near water sources like ponds, lakes, and streams, but some species can also be found in woodlands. The availability of cover and a healthy ecosystem supports their development. A longer lifespan allows for more molts, which are necessary for growth in spiders. Fishing spiders can live up to 2-3 years in the wild, enabling them to reach their full potential size.