Spider plant size, more accurately known as the huntsman spider, refers to the remarkably large body size exhibited by members of the Delena genus, particularly Delena cancerides. These spiders are amongst the largest spider species in Australia, with leg spans reaching up to 15 centimetres. Their size is ecologically significant as it allows them to prey on larger invertebrates and even small vertebrates, influencing local food web dynamics, and their presence often indicates a healthy, undisturbed ecosystem. While visually intimidating, they are generally not considered dangerous to humans.
Scientific Classification and Description
The huntsman spider belongs to the following taxonomic classification: Kingdom → Animalia; Phylum → Arthropoda; Class → Arachnida; Order → Araneae; Family → Sparassidae; Genus → Delena; Species → Delena cancerides. Adult female Delena cancerides typically exhibit a body length of between 20-25 millimetres, while males are smaller, averaging 15-20 millimetres. The most striking feature is their leg span, which can extend to an impressive 150 millimetres (15 centimetres) in females, making them appear significantly larger than their body size suggests. Weight varies considerably depending on recent feeding, but mature females can reach approximately 4-5 grams. Unlike many spiders, huntsman spiders do not possess a prominent silk dragline when moving, contributing to their rapid, erratic movements.
Identifying Features at a Glance
| Feature | Detail |
|---|---|
| Scientific name | Delena cancerides |
| Size (adult) | Body length: 20-25mm (female), 15-20mm (male); Leg span: up to 150mm |
| Endemic range | Eastern and Southeastern Australia - Queensland, New South Wales, Victoria, South Australia, Tasmania |
| Conservation status | Least Concern (IUCN); Not listed under Australian national legislation. |
| Lifespan | 2-3 years in the wild; up to 5 years in captivity. |
Habitat and Distribution in Australia
- Primary biome: Temperate forests, woodlands, and sclerophyll forests, but also frequently found in human-modified environments.
- Geographic range: Found across eastern and southeastern Australia, from the coastal regions of Queensland, through New South Wales and Victoria, extending into South Australia and Tasmania. Their distribution is strongly correlated with the presence of suitable tree hollows and bark crevices.
- Microhabitat: Huntsman spiders prefer to inhabit loose bark on trees, particularly eucalyptus trees, rock crevices, under logs, and within buildings (wall cavities, sheds, garages). Females often establish permanent retreats within tree hollows or under rocks.
- Altitude / depth range: From sea level up to approximately 1,500 metres in mountainous regions.
- Seasonal movement: While not undertaking long-distance migrations, huntsman spiders exhibit seasonal activity shifts. They are most active during warmer months (October-April) for foraging and mating, seeking shelter during colder periods. Interestingly, they demonstrate a unique behaviour of aggregating in large numbers within buildings during periods of high humidity, a phenomenon rarely observed in other Australian spider species.
Diet, Hunting, and Feeding Ecology
Huntsman spiders are opportunistic predators with a broad diet. They primarily feed on insects (beetles, grasshoppers, cockroaches), other spiders, and small invertebrates. Larger females are capable of preying on small lizards, geckos, and even nestling birds. They are ambush predators, relying on their speed and camouflage to capture prey. Rather than building webs for prey capture, they actively hunt, running down their victims. A unique foraging behaviour observed in Delena cancerides is their ability to detect subtle vibrations in tree trunks caused by wood-boring insect larvae. They will then meticulously peel back bark to access and consume these hidden prey items, demonstrating a specialized foraging strategy not commonly seen in other huntsman species.
Reproduction and Life Cycle
The breeding season for Delena cancerides typically occurs during the warmer months, from November to February. Females lay egg sacs containing between 200-400 eggs, which they guard fiercely. The eggs hatch after approximately 3-4 weeks, and the spiderlings undergo several moults before reaching maturity. Gestation is not applicable as huntsman spiders lay eggs. Juvenile development takes approximately 6-12 months, with spiderlings initially remaining close to the egg sac before dispersing to establish their own territories. Females reach sexual maturity at around 18-24 months, while males mature slightly faster at 12-18 months. Males have a significantly shorter lifespan after reaching maturity, often dying shortly after mating.
Unique Adaptations Exclusive to This Species
- Physiological adaptation: Huntsman spiders possess a highly efficient hydraulic system in their legs, allowing them to rapidly extend and retract their limbs for quick bursts of speed. This system relies on hemolymph pressure rather than muscular contraction alone, enabling exceptional agility.
- Behavioural adaptation: Their flattened body shape allows them to squeeze into incredibly narrow crevices, providing protection from predators and access to concealed prey. This adaptation is crucial for survival in their bark-dwelling habitat.
- Sensory adaptation: Huntsman spiders have excellent eyesight for spiders, possessing eight eyes arranged in a configuration that provides a wide field of view and depth perception. This enhanced vision aids in prey detection and navigation, particularly during nocturnal hunting.
Threats, Conservation, and Human Interaction
Despite their large size, Delena cancerides is currently listed as Least Concern. However, they face several threats including habitat loss due to deforestation and urbanization, the introduction of invasive predatory ants (such as the Argentine ant), and potential impacts from climate change altering forest ecosystems. The Australian Museum participates in citizen science projects monitoring spider populations, but there are no specific, dedicated conservation programs solely focused on huntsman spiders. Human interaction is generally limited to occasional encounters within homes, where they are often perceived as pests, though they provide a valuable pest control service.
Frequently Asked Questions
Is spider plant size venomous or dangerous to humans?
While Delena cancerides possesses venom, it is not considered medically significant to humans. A bite may cause localized pain, swelling, and nausea in some individuals, but serious systemic effects are extremely rare. The spider's large fangs can, however, inflict a painful puncture wound. First aid involves cleaning the wound with soap and water and applying a cold compress.
Where is the best place in Australia to see spider plant size in the wild?
Royal National Park in New South Wales, Ku-ring-gai Chase National Park in New South Wales, and Wilsons Promontory National Park in Victoria are excellent locations to observe huntsman spiders in their natural habitat. Look for them under loose bark on eucalyptus trees, particularly during warmer evenings.
What is the difference between spider plant size and similar species?
The giant huntsman spider (Heteropoda maxima) is often confused with Delena cancerides. However, Heteropoda maxima holds the Guinness World Record for the largest leg span of any spider, reaching up to 30 centimetres. Heteropoda maxima is also a different colouration, being more uniformly brown, and is found in more northern regions of Queensland, whereas Delena cancerides is more common in southern Australia and exhibits more mottled patterning on its carapace.