The question of whether a “daddy long legs” can swim is common, stemming from their long legs and tendency to appear in damp areas. The answer is complex because the common name “daddy long legs” refers to three entirely different types of arthropods, each with a unique relationship to water.
Defining the Three Creatures
The term “daddy long legs” confusingly refers to three distinct, unrelated groups of animals: an arachnid order, a true spider, and a true fly. Understanding these classifications is key to accurately answering the question of their aquatic abilities.
The three groups are: Harvestmen (order Opiliones), which are arachnids but not spiders; Cellar Spiders (family Pholcidae), which are true spiders; and the Crane Fly (family Tipulidae), which is an insect.
A key physical difference separates the arachnids from the insect. Both Harvestmen and Cellar Spiders possess eight legs. Harvestmen have bodies fused into a single segment, while Cellar Spiders have two distinct sections. In contrast, the Crane Fly is a true insect with only six legs, a body divided into three segments, and a pair of wings, making it biologically different from the other two.
The Arachnid Answer: Harvestmen and Cellar Spiders
Neither the Harvestman nor the Cellar Spider is adapted to swim, lacking the specialized limbs or body structure for propulsion. These arachnids are primarily terrestrial, and prolonged submersion usually results in drowning. However, their light weight and spindly legs interact uniquely with the water’s surface tension.
The long, thin legs of these creatures distribute their minimal body weight widely, allowing them to temporarily rest on or move across the water’s surface film without breaking it. This effect is similar to a raft floating on a membrane. For Harvestmen, this temporary contact may occur near the edges of puddles or streams, but it is not true swimming.
Cellar Spiders, when dropped into water, may survive for a limited time because their hydrophobic exoskeleton can trap a layer of air, providing an air bubble for respiration. While this adaptation allows for temporary survival, it does not enable them to navigate or swim effectively. The presence of surfactants, such as soap, will break the surface tension and cause them to sink and drown quickly.
The Case of the Crane Fly
The adult Crane Fly, the insect also called a “daddy long legs,” is a clumsy flier and often accidentally lands in water. The adult is not equipped for swimming, and its long legs and delicate body are easily overwhelmed by the water’s surface. Its main focus is mating and laying eggs, often near moist areas.
A significant biological distinction exists in the Crane Fly’s life cycle. While the adult insect is a poor swimmer, its larval stage, often called leatherjackets, is frequently aquatic or semi-aquatic. These larvae are worm-like, legless, and adapted to live submerged or in saturated soil, where they feed on decaying vegetation.
The larvae possess a tough outer skin and sometimes have specialized structures at the hind end to facilitate breathing near the water’s surface. This aquatic survival capability is an adaptation for living near water sources, but it does not transfer to the adult, which remains a land-dwelling insect.