Daddy longlegs have the strongest venom in the world, but luckily their fangs cannot pierce human skin. This common myth, often first heard on elementary playgrounds, is still believed by many adults today. The name daddy longlegs actually refers to both cellar spiders and harvestmen, neither of which are harmful to humans. The harvestmen (Opiliones), our focus this week, don’t even produce venom at all!

 

Harvestman on a leaf.

From afar this may look like a picture of a spider. However, upon closer inspection, it can be seen that this individual is a harvestman. Photo by Marshal Hedin (Flickr).

 

This absence of venom is one of the defining features that distinguishes harvestmen from spiders, another group of visually similar arachnids. Harvestmen are often misidentified as spiders due to the fact that they both have eight legs and share the common name daddy longlegs with one member of the spider family. However, harvestmen do not have segmented bodies or produce silk like spiders do. Harvestmen are actually more closely related to scorpions and pseudoscorpions than spiders, despite their spider-y appearance.

 

While some people may think these multi-legged creatures are gross, they are actually quite clean. Harvestmen regularly groom themselves by performing an action called leg threading in which they slide each leg through their mouth. This allows the harvestmen to remove any parasites that might be attached to their legs. Harvestmen’s legs are essential for walking, eating, smelling, and breathing, and therefore their protection is highly important for survival. By threading their legs, harvestmen effectively safeguard their legs and minimize the threat of parasitism.

 

Daddy long leg on a hand.

A harvestman grooming its legs for parasites. Photo by Dallas Krentzel (Flickr).

 

In order to avoid getting eaten themselves, harvestmen have evolved additional behaviors. Well, a lack of behavior might be more accurate. Because most of their predators rely on movement to hunt, harvestmen benefit by being lazy! A typical day for this critter consists of crawling out of the crevice it calls home to moon-bathe on a nearby leaf, only to return back to its crevice when the sun comes up. Furthermore, if a predator disturbs an individual, the harvestman will curl up and remain motionless, playing dead, to avoid being seen. To repel predators further, harvestmen can excrete obnoxious-smelling chemicals when they sense danger to deter predators. As a last resort, harvestmen can even lose a leg in order to escape being eaten. Unfortunately, unlike other animals that use this escape mechanism, harvestmen’s legs do not grow back.

 

Some scientists believe that aggregating into large clumps further protects harvestmen from predation. Recent research shows that this strange behavior functions less for predation and more for water conservation. Harvestmen are very sensitive to dehydration due to their large amount of surface area. By crowding together, especially when the weather is dry, these bugs are able to conserve their water. The clumps can become enormous, with the largest recorded congregation containing 70,000 individual harvestmen. If 70,000 people were to aggregate, they could fill all of the seats in Gillette Stadium and still have a line of over 1,000 people out of the door.

 

Cluster of daddy long legs.

 Intriguing clustering behavior in which many harvestmen come together to preserve water. Photo by Josef Wells (Flickr).

 

While a huge mass of harvestmen may look like something out of a horror film, these bugs are nothing to be afraid of. As mentioned above, harvestmen are venomless and rely on their front pinchers to squeeze small pray to death. Another means for securing a meal is to scavenge for carcasses left behind by others. Rather than being dormant killing machines as they are described, harvestmen behave more like detritivores (eating decomposing plants, animals, and feces) than active hunters.

 

A harvestman hunting.

A harvestman about to snack on a small collembola, hidden in the top left corner of the photo. To kill collembola, harvestmen crush them with their muscular pinchers. Photo by Marshal Hedin (Flickr).

 

Harvestman eating Diptera (fly) prey.

A feeding harvestman. Since this bee is big, it is likely that it was already dead before the opportunistic harvestman found it. Photo by Marshal Hedin (Flickr).

 

Over the years, harvestmen have inspired an intimidating and persistent false reputation. Now, as harvestmen experts, it is up to you dispel the myths surrounding these harmless creatures and educate your peers on daddy longlegs.

 

 By: Kallin Lang

Feature photo by: John Flannery, Flickr

 

 


Sources
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 Evans, A. 2008. Field Guide to Insects and Spiders of North America. Sterling Publishing Company, New York, New york. pp 404-405.
 Flannery, J. 2011. Harvestman. [Internet] Available from: https://www.flickr.com/photos/drphotomoto/6562222495
 Hedin, M. 2014. Opiliones, Eupnoi, F Sclerosomatidae, Leiobunum nigropalpi, male [Internet] Available from: https://www.flickr.com/photos/23660854@N07/14343985998
 Hedin, M. 2014. Opiliones, Dyspnoi, F Sabaconidae, Sabacon sp immature (probably S. occidentalis). [Internet] Available from: https://www.flickr.com/photos/23660854@N07/14808995458
 Hedin, M. 2009. Opiliones, Eupnoi, F Sclerosomatidae, Leiobunum vittatum group, male with prey. [Internet] Available from: https://www.flickr.com/photos/23660854@N07/3679665965
 Krentzel, D. 2012. Vonones ornate (Cosmetidae)-Time to groom. [Internet] Available from: https://www.flickr.com/photos/31867959@N04/6955043814
 McCarthy, E. 2014. 15 Fascinating facts about daddy longlegs [Internet]. Mental Floss. Available from: http://mentalfloss.com/article/59455/15-fascinating-facts-about-daddy-longlegs
 Viegas, J. 2014. Clump of Spiders? Viral video shows something else. [Internet]. Discovery News. Available from: http://news.discovery.com/animals/insects/clump-of-spiders-viral-video-shows-something-else-140102.htm
 Wells, J. 2014. 2014:07:06-13:47:12. [Internet] Available from: https://www.flickr.com/photos/josefwells/14662749639
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