Many people regularly encounter long-legged arachnids in their homes and gardens, often curious about why these creatures seem so numerous. This common observation prompts questions about their identity and the conditions that allow them to flourish. Understanding the different types of “daddy long legs” and their survival strategies helps explain their widespread presence.
Unpacking the “Daddy Long Legs” Identity
The common name “daddy long legs” refers to two distinct groups of arachnids: harvestmen (Order Opiliones) and cellar spiders (Family Pholcidae). While both possess notably long, thin legs, they are biologically different. Harvestmen have a body that appears as a single, fused segment, and they do not produce silk or venom.
Conversely, cellar spiders are true spiders with a distinct two-part body, comprising a cephalothorax and abdomen. They construct loose, irregular webs for catching prey and possess venom glands, though their venom is typically weak.
Biological Factors Behind Their Numbers
Harvestmen thrive due to their generalist omnivorous diet, consuming small insects, mites, fungi, and decaying organic matter. They possess chewing mouthparts, allowing them to ingest solid food particles. Their ancient lineage, dating back over 400 million years, suggests a highly successful and adaptable body plan that has remained largely unchanged. Some species also form large aggregations, offering protection against predators and reducing water loss.
Cellar spiders are prolific reproducers, with females laying multiple egg sacs, each containing numerous spiderlings that disperse after hatching. They are opportunistic predators, capable of surviving on a wide range of small prey, including flies, mosquitoes, and even other spiders. Their ability to capture prey larger than themselves, coupled with a relatively long lifespan in stable conditions, contributes to their population success.
Why They Thrive in Human Environments
Human dwellings and surrounding areas provide an ideal habitat for both harvestmen and cellar spiders. These structures offer stable temperatures and shelter from harsh weather conditions and predators, creating a relatively safe environment. Basements, cellars, and undisturbed corners often have the damp, dark conditions preferred by cellar spiders, enabling them to build their characteristic messy webs.
The presence of insects like flies and mosquitoes provides a consistent food source for cellar spiders. Harvestmen find detritus and moist areas under rocks, logs, or in leaf litter around homes. The undisturbed nature of many indoor spaces, like basements and attics, allows these arachnids to establish populations.
Their Ecological Role and Harmless Nature
Neither harvestmen nor cellar spiders pose a danger to humans. Harvestmen do not produce venom and lack fangs, making them harmless. While cellar spiders do possess venom, it is mild and their fangs are too short to penetrate human skin. Bites from cellar spiders are rare and result in minimal or no reaction.
Both groups play beneficial roles in ecosystems. Cellar spiders are effective pest controllers, preying on nuisance insects like mosquitoes and flies, and consume other spiders, including black widows. Harvestmen contribute as scavengers by breaking down organic matter and act as generalist predators of small invertebrates. They help manage other insect populations.