Pisaurina mira
(Walckenaer, 1837)
American nursery web spider, nursery web spider
Pisaurina mira is a large, abundant nursery web spider found across eastern North America. Females measure 12.5–16.5 mm in body length, males 10.5–15 mm, with leg spans reaching 35–45 mm. The is distinguished by its unique arrangement: four eyes in a straight row and four eyes in a U-shape. Unlike wolf spiders, which they resemble, P. mira is typically found on vertical vegetation rather than on the ground. The species exhibits notable reproductive including male silk-wrapping of females to avoid sexual , and female construction of nursery webs to protect spiderlings until their first .
Pronunciation
How to pronounce Pisaurina mira: /piː.saʊˈriː.na ˈmɪ.ra/
These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.
Identification
Distinguished from similar wolf spiders (Lycosidae) by arrangement: Pisaurina has all eyes approximately same size in two rows ( four straight, four U-shaped), versus wolf spiders with two large posterior eyes. P. mira is more commonly found on vertical vegetation (weeds, shrubs, trees) rather than on ground. Distinguished from slender crab spiders (Philodromidae, e.g., Tibellus) by overall body proportions and eye arrangement. From other Pisaurina : P. dubia has central tuft of hair projecting between anterior eyes like tiny horn, and is generally smaller (12–15 mm).
Images
Appearance
Moderately high protecting the . moderately long, typically less than twice the length of carapace. Sexually dimorphic: males have longer legs and greater leg length to body ratio than females. Coloration ranges from light brown, beige, or grayish with a broad dark stripe down the body, to indistinct median band with two rows of lateral spots. specimens often lack the distinct stripe. All eight approximately same size, arranged in two rows: four in straight line, four in U-shape. Often rests with first two pairs of legs held tightly together.
Habitat
Inhabits ecotonal areas—transitional zones between woods and fields, forest edges, understory vegetation. Found in tall grass, shrubs, bushes, grapevines, and low vegetation in wetlands. Occasionally found on lawns, in barns on hay bales, on exterior of homes, and rarely indoors. Prefers vegetation at least a few inches off ground for nursery web construction. In southeastern U.S., has been observed in pitcher plants and on Spanish moss.
Distribution
Eastern North America: southern Ontario and Quebec (Canada) south to central Florida and Rio Grande Valley of Texas; west to Minnesota, Nebraska, Kansas, and Oklahoma. Core range in eastern deciduous forest region.
Seasonality
reach maturity in spring (April–May). Mating occurs mid-June to mid-July. hatch in May; spiderlings disperse from nursery webs after first in June. spiders overwinter in cracks, crevices, beneath loose bark or stones. Highest adult male activity in May–June.
Diet
Active sit-and-wait ambush . Preys on small insects including gnats, mosquitoes, and other small arthropods. Uses to seize prey. Injects digestive juices to liquefy internal organs, consuming resulting fluid. Contributes to agricultural pest control by consuming (Lygus lineolaris) and other crop pests.
Life Cycle
(one per year). Female carries sac secured by silk thread to and held by . Prior to hatching, female builds nursery web by gathering leaves, suspends egg sac within web. Spiderlings hatch and remain in nursery web until first . Female guards nursery web throughout this period. Spiderlings disperse after first molt, overwinter as immatures, reach maturity following spring.
Behavior
Sit-and-wait ambush , often motionless on vegetation day and night. May hunt actively, including at outdoor lights. Superior motion detection despite small ; responds quickly to prey or flees from danger. Mating: male follows female's dragline, approaches from behind. Both spiders hang from draglines during mating; male wraps female's legs I and II in silk while holding legs III and IV, rotating female 3–5 times. Male offers (prey wrapped in silk) prior to copulation. Successful males mate with multiple females (up to 5) in short time frames (single night to 72 hours).
Ecological Role
of small insects and agricultural pests. Reduces herbivory, indirectly increasing plant carbon storage by altering grasshopper foraging . Contributes to of in small fruit and vegetable crops.
Human Relevance
Common in yards, gardens, farms, and orchards throughout eastern U.S. Not dangerously venomous to humans or pets; venom lethal only to small prey. Highly beneficial as of insect pests. Frequently encountered by humans due to abundance and spring activity period. Often mistaken for wolf spiders, causing unnecessary alarm.
Similar Taxa
- Lycosidae (wolf spiders)Similar size, coloration, and ground-dwelling appearance, but wolf spiders have two enlarged and are typically found on ground rather than vertical vegetation.
- Pisaurina dubiaSmaller with central tuft of hair between ; often found in similar but with more southerly distribution.
- Tibellus (slender crab spiders)Similar lanky build and striped pattern, but crab spiders have laterigrade legs (capable of sideways movement) and different arrangement.
Misconceptions
Frequently mistaken for wolf spiders due to size and general appearance. Not dangerously venomous to humans despite intimidating size. The name 'nursery web spider' refers to female parental care web, not a prey-capture web—this does not build webs for hunting.
More Details
Heat sensitivity
Exhibits lower heat than wolf spiders (Tigrosa helluo), with critical thermal maximum of approximately 34°C. Predatory performance decreases at warmer temperatures due to increased metabolic stress and energy demands.
Sexual dimorphism in leg length
Male leg length is sexually selected: longer legs associated with greater copulation success and lower risk of sexual , as legs play crucial role in immobilizing females during mating.
Silk use
Unlike web-building spiders, P. mira uses silk primarily for : draglines during mating, wrapping female legs to prevent , constructing nursery webs, and securing sacs. Minimal 'scaffolding' silk used for ambush perches.