A group of daddy long-legs of the order Opiliones.
Credit: Creative Commons | Luis Fernández García
Daddy longlegs is a term used to refer to three different types of critters, and only one of them is a spider. Also, a common belief that daddy longlegs spiders are the most venomous spiders in the world is an urban myth.
Harvestmen & crane flies
The term most properly refers to an arachnid in the order Opiliones. They are also called harvestmen. This outdoor arachnid typically lives under logs or rocks. Unlike spiders, it has only one pill-like body segment. It also has only two eyes, does not spin webs, and is not venomous. Like the spider, it has eight very long legs that can be 30 times as long as its body.
In the Southern United States as well as some parts of Canada and the United Kingdom, the crane fly is also sometimes called a daddy longlegs.This distinctive bug, with six long legs and two large wings, is not a spider, nor an arachnid, but is an insect.
Another creature often called daddy longlegs is a spider in the family Pholcidae. The common name for these creatures used to be cellar spiders, but arachnologists have started to call them "daddy longlegs spiders" because of the common confusion.
This daddy longlegs has two body segments — a cephalothorax and an unsegmented abdomen — and eight eyes. It ranges in color from cream to brown or gray, and some species have brown stripes. The daddy longlegs’ characteristic long, skinny legs are several times the length of its small body. They have dark spots at the knees and contain sensors that detect movements and vibrations. The daddy longlegs spider can range from 2 to 10 mm long, but its legs can grow up to 50 mm. The female is slightly bigger than the male.
Daddy longlegs spider habits
Daddy longlegs spiders live on every continent except Antarctica. They prefer damp climates but can nevertheless thrive in deserts. They are especially successful in urban areas where they spin thin, tangled webs in ceiling corners, under furniture, in garages and basements, and other places where they’re unlikely to be disturbed. Daddy longlegs may be useful spiders because they can help keep the population of other insects and spiders down.
The daddy longlegs spider’s web does not have adhesive properties for catching prey. Instead, insects and other spiders get trapped in the confusing, irregular web structure. When a daddy longlegs sees prey trapped inside its web, it throws a length of silk over the prey from a distance. That stops the prey from moving. Then, the daddy longlegs covers the prey with silk and administers its fatal bite. This technique allows the daddy longlegs spider to catch prey much larger than itself.
Daddy longlegs spiders can mate throughout the year. The male squirts sperm onto the web then sucks it up into his pedipalps. It then inserts the pedipalps into the female’s epigynum, and she carries the sperm around with her until she lays her eggs. The female carries her egg sac in her jaws at all times — with the exception of eating — until the eggs hatch.
Male daddy longlegs typically live for about one year and die after mating. Females can live for three years.
Venom myth busted
According to urban legend, daddy longlegs are the most venomous spiders in the world, but their fangs are too weak to penetrate human skin. However, this myth was busted on the Discovery Channel show "Mythbusters." A daddy longlegs spider was coaxed into biting the arm of the show's co-host, Adam Savage. He reported nothing more than a very mild burning sensation from the spider's venom that lasted just a few seconds.
The myth may have come about because the daddy longlegs spider can kill the dangerous Australian redback spider, but that is done through its ingenious web-catching technique, not its venom.