Part II: Truth about daddy longlegs

So we’ve already established  in the previous post that daddy longlegs, also known as harvestmen, are NOT spiders.  So let’s go ahead and tackle another big myth surrounding daddy longlegs.

Longlegs Fact #2: Daddy longlegs are NOT venomous.

Daddy longlegs have no venom glands or fangs despite that rumor you may have heard that “daddy longlegs are the most venomous spider in the world, but their fangs are too small to penetrate our skin”.  Whereas spiders are fluid feeders (the venom has enzymes that digest the tissue first and then the spider sucks up the fluids), daddy longlegs are whole feeders (they tear apart their food with their chelicerae).  The chelicerae of harvestmen are pincer-like with one stationary and one movable claw, however, they cannot bite and are in no way harmful.  In contrast, the chelicerae of a spider are the pair of fangs which inject venom.

So where does this rumor come from?  Well some people suggest that it has to do with the confusion of overlapping common names – which is one reason why scientists use Latin names and have many rules that they must follow when formally naming a species (for animals, these guidelines are established by the International Commission on Zoological Nomenclature).

In Ireland, for example, the common name “daddy longlegs” refers to crane flies.  So it is obvious how common names may be a sources of confusion, but it doesn’t explain how we have managed to incorrectly label daddy longlegs as “the most venomous spider in the world”.

Spiders belonging to the family Pholcidae look very similar to a daddy longlegs (see the picture of a pholcid below)!  These spiders (true spiders, belonging to the order Araneae) are called “daddy longlegs spiders” and they do have venom, but this venom is relatively harmless to humans and a bite would be like a bee sting for many people.  Pholcid spiders will prey on other spiders which may cause people to assume that pholcids are in turn harmful, or even deadly.  So it is possible that the myth originated from something along these lines.

Below are some images showing more of the very colorful and diverse tropical species (first and second images), a species from North Carolina demonstrating the stereotypical temperate species of daddy longlegs, and an example of a pholcid (which is a spider and NOT a daddy longlegs).

Cynorta annulata, Costa Rica

Undescribed species of Cosmetidae, Costa Rica

Leiobunum vittatum, North Carolina

A spider belonging to the family Pholcidae. It is often confused with true daddy longlegs (Opiliones).