Friday, July 29, 2011

The Truth Behind Daddy Longlegs

By: Lacy Sellent, Writing Fellow at the Cable Natural History Museum
Growing up, I heard a lot of “facts” about the natural world.  One particular “fact” about daddy longlegs really stuck in my head.  The rumor was that if daddy longlegs had mouths big enough to bite humans they would the most poisonous spider in the world.  This is something I believed for quite some time—until I learned the real truth…   

One problem with this legend is that daddy longlegs (also known as harvestmen) are not poisonous to humans.  In fact, they have no venom whatsoever.  However, it is true that their mouths are too small and their jaws are too weak to bite humans.  Apart from not being venomous in the first place, another reason why daddy longlegs are not the most poisonous spider in the world is because they’re not even spiders!  Daddy longlegs and spiders are more like cousins to each other.

Scientists classify all living things in a hierarchical system with seven or more different levels.  Organisms are put into groups based on shared characteristics, which often reflect how closely they are related to each other.  The top category is the broadest and then each subsequent category gets more specific. Spiders and daddy longlegs both are in the kingdom Animalia, the group to which all animals belong. They also share the phylum Arthropoda with insects and crayfish. They share the class Arachnida with ticks and scorpions. The next category is order. All spiders make up the order Araneae, while daddy longlegs make up the order Opilione. That order is divided further into families, genera, and finally into over 6,400 individual species of harvestmen has been discovered worldwide.

Both spiders and daddy longlegs have a hard outer shell called an exoskeleton instead of a backbone, eight jointed legs, and segmented bodies. Unlike spiders, daddy longlegs are not capable of spinning webs. They don’t even have any silk glands!  And while spiders have eight eyes, daddy longlegs only have two. They also differ from spiders in their eating habits. Daddy longlegs catch food and eat it outside their mouth, because that’s where their teeth are located.  After a meal, daddy longlegs clean up from the messy task.  After a quick swipe of their legs through their jaws the daddy longlegs is clean and ready to get on with its day. Or, rather, its night. 

Daddy longlegs generally hunt at night—searching through leaves and other debris.  Daddy longlegs will eat anything from plant matter to worms and small insects. They can be handy around a garden, because they’ll help keep pesky insects, such as aphids, away. The name Opilione (to which the daddy longlegs belongs) is Latin for “aphid sucker.”

While out looking for food, daddy longlegs use their legs to sense danger. Any vibration made by approaching trouble is picked up through their extra-sensitive legs. These legs are also used for tasting and smelling. If a daddy longlegs finds itself in trouble, it has two legs that can give off a nasty odor.  Not many predators care for a smelly dinner. 

They also have another trick—when trapped, they can release the captured leg!  Once a daddy longlegs realizes there is no other way out, it uses a special muscle to dislodge the leg from its body. Then the muscle closes around the stump and the daddy longlegs scurries off to safety.  Meanwhile, the foe is left with a squirming leg.  The lost leg may twitch for several minutes.  This distracts the predator—ensuring the daddy longlegs a safe getaway.  

Daddy longlegs are harmless creatures that are often misunderstood.  They are not poisonous, and they are not spiders.  We don’t need to fear them.  We just have to get to know them.

For over 44 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 13470 County Highway M. The new exhibit, The Joy of Birds: Feathers in Focus opened in May, 2011. Find us on the web at to learn more about our exhibits and programs. Also discover us on Facebook, or at our blogspot,

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