What Are Harvestmen, a.k.a. Daddy-Long-Legs?

On his current expedition, Ronald Clouse ventures into the jungles of the Philippines to study harvestmen, or daddy-long-legs, of the order Opiliones. By collecting data for phylogenetic analysis, he hopes to learn more about the history of these creatures and the lands they inhabit.

A Jeepney in Manila. Jeepneys are a main type of inexpensive transportation throughout the Philippines. (Photo by Ronald Clouse)
A Jeepney in Manila. Jeepneys are a main type of inexpensive transportation throughout the Philippines. (Photo by Ronald Clouse)

Our decision to leave Panay Island early in the hopes of arranging some other excursions didn’t work so well, and the week spent in Manila saw our plans change almost daily. Dave was able to go to Cavinti, Laguna via a long bumpy motorcycle ride, where he collected some great harvestmen, including two sandokanids. Our trip to Mt. Malindang on Mindanao was called off for safety reasons, as kidnappings in the region continue to be a major threat. Still, the time in Manila may have been a blessing in disguise, as it allowed me the opportunity to communicate with my family just when my father passed away. Not unexpected, but still a sad event, it was good to have a measure of closeness to others via the internet. Now, on June 7th, we are traveling to Mt. Bulusan in the southern end of Luzon, where we will camp and collect for a week. From there we go to Davao City on Mindanao, very close to where the mysterious Cyphophthalmi harvestmen juveniles were collected by Dr. Arvin Diesmos in 2009.

This brings me to an important topic which we should discuss now, which is: What exactly are harvestmen? Called daddy-long-legs in the U.S., they are often called spiders, and many people believe they are dangerous, but both are untrue. Like spiders, harvestmen are arachnids, members of class Arachnida, but they are in a different order from spiders. In fact, harvestmen are not even that closely related to spiders; their closest related arachnids are scorpions.

An Opiliones in the suborder Eupnoi, from Brazil. (Photo by Ronald Clouse)

How can you tell the difference between a harvestman and a spider? The easiest way is to look for a narrow constriction between the front part (with the legs and eyes and mouth) and the rear part. If there is a constriction, it’s a spider. Spiders also make silk, but harvestmen do not.

The only adult member if the Opiliones suborder Cyphophthalmi collected from the Philippines, from Palawan, dorsal view. (Photo credit Harvard University, Cyphophthalmi Checklist, Prof. Gonzalo Giribet. )
The only adult member if the Opiliones suborder Cyphophthalmi collected from the Philippines, from Palawan, dorsal view. (Photo credit Harvard University, Cyphophthalmi Checklist, Prof. Gonzalo Giribet. )

There are three kinds of harvestmen that live in the Philippines. These are in the suborders Eupnoi (the same suborder that contains the long-legged species people see in their basements and around old wood), Laniatores (which have evolved into spectacular forms in South America), and Cyphophthalmi. The last kind live all over the world, deep in humid leaf litter, where they look a lot like little seeds. They are rare in the Philippines, though, known only from four specimens, only one of which is a male. Because they do not normally (or perhaps ever) cross large bodies of water, they are excellent evidence of past land connections.

An Opiliones in the suborder Laniatores, from Brazil. (Photo by Ronald Clouse)
An Opiliones in the suborder Laniatores, from Brazil. (Photo by Ronald Clouse)

Opiliones has been around for over 400,000,000 years, and early fossils look very much like the forms alive today. Follow the video links to see more details about the geologic history of the Philippines and the taxonomy of harvestmen.

The only adult member if the Opiliones suborder Cyphophthalmi collected from the Philippines, from Palawan, lateral view. (Photo credit Harvard University, Cyphophthalmi Checklist, Prof. Gonzalo Giribet)
The only adult member if the Opiliones suborder Cyphophthalmi collected from the Philippines, from Palawan, lateral view. (Photo credit Harvard University, Cyphophthalmi Checklist, Prof. Gonzalo Giribet)

The Philippines, then and now:

What are daddy-long-legs?

Cyphophthalmi Checklist link:
http://giribet.oeb.harvard.edu/Cyphophthalmi/

Read all posts by Ronald Clouse: http://newswatch.nationalgeographic.com/author/ronaldclouse/

Changing Planet

,

Ronald Clouse investigates the histories of invertebrates found in the leaf litter. He works mostly with arthropods in the Indo-Pacific, especially harvestmen (daddy-long-legs) and ants. He also works with harvestmen in Brazil and the southern U.S., and he is interested in the processes by which we reconstruct history using DNA and morphology.