9 Surprising Facts About Daddy Longlegs

Daddy longlegs aren't spiders and they don't have venom

Daddy longlegs standing on a leaf

Natursports / Shutterstock

Daddy longlegs, also called harvestmen, may number 10,000 species, of which scientists have documented roughly 6,500. They inhabit moist, dark places like tree trunks, leaf litter, and caves on every continent except Antarctica. The greatest diversity of harvestmen species live in the tropics.

IUCN lists 21 species as threatened, with 14 as endangered or critically endangered. Unfortunately, five species are already extinct. The actual number of threatened species is unknown due to the lack of a comprehensive assessment of the taxa.

Learn more surprising facts about them, such as what truly happens when they lose a leg and how they catch prey.

1. Daddy Longlegs Aren't Spiders

First, daddy longlegs make up the order Opiliones and aren't spiders. They are arachnids, but so too are mites, ticks, and scorpions.

Omnivorous daddy longlegs have pill-shaped bodies. They consume plants, fungi, carrion, and invertebrates, including other arthropods and snails. Unlike spiders, they can't make silk for spinning webs.

Spiders have two segments to their bodies, and most eat only insects and other spiders. They have eight eyes, while daddy longlegs have two. Cellar spiders are often confused with daddy longlegs because of their long, spindly legs. They also have segmented bodies and build webs that identify them as spiders. People may call them daddy longlegs, but they aren't true daddy longlegs.

2. They Aren't Venomous

A common urban myth is that daddy longlegs have the most toxic venom of all spiders, but their fangs are too small to bite. Even if they were spiders, they don't have venom glands or fangs.

An episode of the television show "MythBusters" debunked the daddy longlegs myth with a bite experiment. Unfortunately, they didn't explain that those were cellar spiders from the order Pholcidae, not true daddy longlegs.

3. They Can't See Very Well

Daddy longlegs have simple eyes mounted on eye turrets attached to their bodies. These eyes act as light sensors and do not appear to provide more than blurry images.

Research shows that cave harvestmen are most receptive to the light emitted by the glowworms that make up their diet. Harvestmen learn about the world around them using the sensitive tips of their legs as sense organs.

4. They Are Ancient

The Opiliones first appeared a long time ago and have barely changed at all over millions of years. Fossils dating back 400 million years, before dinosaurs roamed the earth, look very similar to today's daddy longlegs.

Because of their extensive history, researchers use daddy longlegs fossils for evolutionary and biogeographic studies. Scientists even can trace Panagea splitting into separate continents through the evolutionary divergences in Opilionid fossils.

5. Their Legs Don't Grow Back

Another myth is that their legs grow back. During the average lifetime, daddy longlegs have a 60 percent chance of losing one or more legs. This can happen when a predator pulls them off or when the harvestman chooses to detach the appendage. Their gait then permanently changes.

Typically, they use the two longest legs as feelers, then alternate the other six legs with three legs touching the ground at any one time. Their bodies bounce up and down like a dribbled basketball when missing a leg. If two or more are missing, the dribbling basketball turns into a more extreme bobbing motion.

6. They Have a Range of Defenses

Detaching their legs isn't the only or even primary way they escape predators. Daddy longlegs prefer to blend in with their surroundings and play dead. Warning predators away with a foul-smelling liquid from their exocrine glands is another defense. The glands are unique to these arachnids and are also used to communicate with other harvestmen. Some species have armored bodies that protect them from predation.

7. They Use Glue to Catch Their Dinner

Daddy longlegs have small, hairy appendages near their mouth used as sensory organs called pedipalps. Using high-speed cameras, researchers discovered the hairs on the pedipalps secrete a glue-like substance to capture prey. They embrace their mark with their pedipalps and apply the secretion in milliseconds. With only a few microscopic drops, the glue can disable organisms twice the harvestman's size.

8. They Cluster Together to Stay Warm

cluster of daddy longlegs on a rock

Blake Burkhart / Flickr / CC BY 2.0

Groups of daddy longlegs sometimes form thick clusters called aggregations. Aggregations contain three or more huntsmen, with one enormous assemblage containing 300,000 individuals.

Once created, the mass can stay in place for months, particularly during winter. Researchers speculate that aggregations form for mating, temperature control, humidity control, or to deter predators. These clusters can repel predators through their collective scent. If a predator continues to threaten the daddy longlegs, the whole aggregation starts a disorienting bobbing motion before the individuals scatter.

9. Some Species Are Endangered

Of the thousands of Opiliones, six are listed as critically endangered and possibly extinct, eight are endangered, and two more are vulnerable. The threats affecting the animals are primarily habitat destruction and degradation. Several species are threatened by the Ceylon cinnamon cultivation taking place in Seychelles. These invasive trees make the habitat unsuitable for endemic species. Another species is threatened by coffee monoculture.

In other areas, loss of cave habitats, either through cave tourism or urban development, is a significant issue. The Bone Cave Harvestman in Texas is one species endangered due to the loss of habitat. Development of the land the caves occupy and pollution entering the cave habitat via runoff is an ongoing issue.

Save the Daddy Longlegs

  • Avoid damaging caves through eating or drinking in them.
  • Choose shade-grown coffee.
  • Support legislation to research and protect Opiliones.
  • Help fund the IUCN Red List Barometer of Life.
View Article Sources
  1. Pinto-da-Rocha, Ricardo, et al. (Editors). “Harvestmen: The Biology of Opiliones.” Harvard University. 2007.

  2. Lehmann, Tobias, et al.  “The Visual System of Harvestmen (Opiliones, Arachnida, Chelicerata) – A Re-Examination.” Front Zool, vol. 13, 2016, doi:10.1186/s12983-016-0182-9

  3. Palencia, Lorena, et al.  “First Fossil Harvestmen (Arachnida: Opiliones) from Spain and Notes on the Fossil Record of Opiliones.” Palaeontol Electron, 2019, doi:10.26879/855

  4. Fernández, Rosa, et al. “The Opiliones Tree of Life: Shedding Light on Harvestmen Relationships through Transcriptomics.” Proc R Soc B, vol. 284, 2017, doi:10.1098/rspb.2016.2340

  5. de Silva Souza, Elene, and Rodrigo H. “Harvest-Ironman: Heavy Armature, and not Its Defensive Secretions, Protects a Harvestman Against a Spider.” Animal Behaviour, vol. 81, 2011, pp. 127-133., doi:10.1016/j.anbehav.2010.09.023

  6. Wolff, Jonas O., et al. “Gluing the “Unwettable”: Soil-Dwelling Harvestmen Use Viscoelastic Fluids for Capturing Springtails.” Journal of Experimental Biology, vol. 217, 2014, pp. 3535-3544., doi:10.1242/jeb.108852

  7. Mukherjee, A., et al. “First Report on Mass Aggregation of Opiliones in China.” J Threat Taxa, vol. 2, 2010, pp. 892-893., doi:10.11609/JoTT.o2296.892-3

  8. Alviola, Geonyzl Lepiten. “Diversity of Spiders in Three Habitat Types in Impasug-Ong Protected Area, Bukidnon, Philippines.” EEB, vol. 2, 2017, doi:10.11648/j.eeb.20170206.12