The sight of a daddy longlegs scurrying across your backyard can be unnerving—typically the spindly legs of these creatures, also called harvestmen, are an inch or two long. But how would you feel about finding a giant one in a dark cave?
On a recent trip to Laos, Dr. Jäger discovered a very leggy harvestman whose leg span is more than one-foot wide (about 33-plus cm). Experts are still working to properly identify it on a species level.
Often misidentified as spiders, harvestmen belong to their own, separate order—the Opiliones. They are arachnids but are distant “cousins” to true spiders. They both have eight legs, but very different bodies. Harvestmen’s bodies usually look like one big round or oval segment, while spiders’ bodies have two very distinct sections. Another difference: Harvestmen do not spin webs (they can’t produce silk).
The Huge Harvestman
Dr. Jäger was in Laos in April to film a major TV production. “In between takes I collected spiders from the caves in the southern province of Khammouan. In one of the caves I discovered a harvestman that was absolutely huge.”
The leg span of the gigantic male harvestman was more than one foot (slightly more than 33 cm) putting it in close contention for the world’s largest. The current record-holder is a South American harvestman with one-foot-one-inch leg span (just over 34 centimeters).
The giant huntsman is not the first giant “creepy crawly” to be found in Laotian caves. Other arthropods with supersized dimensions have been found in the same region – the Laotian huntsman spider Heteropoda maxima with a leg span of up to 11 inches (30 cm), the whip scorpion Typopeltis magnificus with a span of 10 inches (26 cm) and the predatory centipede Thereuopoda longicornis with a total span of almost one foot, three inches (about 40 cm).
“What mechanisms or factors are responsible for this frequency of gigantism is still unclear,” says Jäger. The only thing that seems certain is that there is a limit to growth—either due to the lack of oxygen supply to the long appendages or because when speed becomes reduced when legs grow too long to flee or catch prey effectively.
The Arachnid With No Name
Dr. Jager’s find was one of many specimens collected in the cave, and the giant harvestman remained hidden among the other organisms. Only one the findings were sorted and labeled did he realize he had a giant discovery on his hands. But efforts to positively identify the species have been inconclusive so far.
Jäger’s speciality is not harvestmen, but huntsman spiders. “In attempting to categorize the harvestman properly, however, and give it a scientific name, I soon reached my limits,” says Jäger. He consulted specialist Ana Lucia Tourinho from the National Institute for Research of the Amazon (INPA) in Manaus, Brazil, who is currently a visiting academic at the Senckenberg Arachnology lab. Together, they could only conclude that it is probably the genus Gagrella in the Sclerosomatidae family.
“It’s a shame we can’t identify such an exceptional discovery correctly, i.e. its species,” says Jäger. “We haven’t dealt with these and related genera from China and neighboring South East Asia before. Specialists are also unavailable due to the fact that descriptive taxonomy is no longer the main focus of research funding.”
Jäger and his team feel that the harvestmen of the Sclerosomatidae family have invaluable research potential because specimens can be found in virtually every habitat and constitute an ecologically important predator group in the natural food chain. Hunstmen could serve as an indicator of the ecological state of the natural and cultural scenery.
Dr. Jäger would now like to continue to investigate the Sclerosomatidae family along with his Brazilian colleague and in collaboration with other scientists in Germany, China and Japan. The findings should then be applicable to other groups and regions. “We want to avoid a situation in future where we again lack the experts to classify such unique creatures,” says Jäger.