Bola Spider, Bolas Spider
Mastophora cornigera
Araneidae (Orb-Weavers), Order Araneae
Physical Description
The bolas spider is famed for its remarkable morphology. Females exhibit extreme sexual dimorphism, growing much larger than males with a distinctively swollen, pear-shaped or triangular abdomen that often bears horn-like or shoulder tubercles. The body surface can be warty or wrinkled, closely resembling bird droppings.
Size Estimate
Females range from 10 to 15 mm in body length, while males are tiny dwarfs measuring only about 2 mm. The leg span is relatively compact for an orb-weaver relative to its heavy body.
Coloration & Markings
Coloration typically includes mottled shades of white, cream, gray, and dark brown, perfectly adapted for camouflage against bark, leaves, or to mimic animal droppings on foliage.
Web Type
Bolas spiders do not build traditional orb webs. Instead, adult females construct a single silk thread called a bolas line, weighted at the end with a sticky globule of silk.
Eye Arrangement
Typical araneid arrangement featuring eight eyes in two rows, with the lateral eyes often paired on tubercles and median eyes situated on a raised central ocular quadrangle.
Leg Characteristics
The front legs are long and robustly built for swinging and holding the specialized sticky bolas line, while the rear legs are shorter and adapted for gripping vegetation.
Venom & Safety Information
Venom Information
Possesses mild venom used to quickly immobilize captured moths. The venom is not toxic to humans and poses no medical threat.
Medical Significance
Harmless to humans. These spiders are extremely docile and rarely bite, possessing mouthparts too small to easily pierce human skin, and their venom holds no medical significance.
Safety Recommendations
No special precautions needed. These spiders are harmless, docile, and rarely encountered due to their nocturnal habits and camouflage. If found indoors, gently relocate outdoors using a cup and paper.
Habitat & Behavior
Habitat & Range
Found across North and South America, typically inhabiting deciduous forests, woodland edges, orchards, and overgrown gardens where they rest on leaves and branches.
Behavior & Temperament
Strictly nocturnal hunters. During the day, they remain motionless in a defensive, camouflaged posture. At night, they actively swing their sticky silk droplet to catch flying prey.
Diet & Prey
Specialized exclusively on adult male moths. The spider produces volatile chemical compounds that mimic the sex pheromones of specific moth species, luring them within striking range.
Seasonal Activity
Most active during warm summer and autumn nights. Adults overwinter through hardy egg sacs, with new generations hatching in spring.
Description
The bolas spider is one of nature's most fascinating master illusionists. Eschewing the traditional stationary web of its araneid relatives, this nocturnal hunter uses chemical mimicry and an active swinging weapon to capture prey. By releasing synthetic moth pheromones, the female draws male moths close before hurling a sticky silk globule attached to a single thread.
Key Features
Distinguished by its specialized nocturnal hunting method using a single sticky bolas line, chemical pheromone mimicry, horn-like abdominal tubercles, and bird-dropping camouflage.
Similar Species
Other members of the genus Mastophora, which can be distinguished primarily through subtle differences in abdominal ornamentation, geographic distribution, and the specific moth species they target.
Life Cycle
Females produce brown, papery egg sacs attached to twigs during autumn. Spiderlings emerge the following spring, dispersing via ballooning. Males mature rapidly, while females undergo multiple molts.
Ecological Importance
Acts as a specialized nocturnal predator controlling specific moth populations, contributing to the delicate balance of forest and woodland insect webs.
Conservation Status
Not evaluated by the IUCN, but populations remain generally stable where suitable native woodland and forest habitats persist.
Interesting Facts
Bolas spiders are renowned for practicing chemical espionage. They do not merely attract any moth; different species of Mastophora produce distinct pheromone blends tailored to attract specific species of male moths.
Photography Tips
Best photographed at night using a macro lens and a ring flash or off-camera diffusion. To capture their unique hunting behavior, observe them on foliage after dusk when they begin spinning their bolas line.
Identified: 2026-10-18T23:00:25.997664