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Jan. 25, 2012

Solifuge Arachnids (that's Latin for awesome)

by The Bug Chicks

Click to enlarge images

This Zeria fordi female from Lake Bogoria, Kenya is chomping on a grasshopper. This particular solifuge ate everything we offered her, including poisonous millipedes!

Solifuges (also called camel spiders, wind scorpions or sun-spiders) are ancient, nonvenomous arachnids in the Order Solifugae. They are related to true spiders and scorpions and the other members of the Class Arachnida (I like to think of them as cousins). They are easily identified by their huge forward facing jaws, called chelicerae. Unlike spiders and scorpions that use venom to kill their prey, solifuges use their powerful chelicerae to crush and macerate their prey. Then they use their rostrum (an organ that operates like a straw) to suck down and filter all of the juices of the crushed food.

Solifuges have some unique structures on their bodies that other arachnids don't have. Males of most families have a flagellum on the inside of their jaws. It's a little appendage that varies greatly in size and shape, from short stubs to an elaborate, membraneous, rotating structure. This organ helps arachnologists to identify these animals to the species level. Its function is not known, but we think it may play a role in mating.

This is the inner (mesal) surface of the chelicerae of a male solifuge. The flagellum is the membraneous section that sticks up like a flag. (Photo by Heather Cummins and Kristie Reddick)

The tip of the flagellum. Some can be very ornate. (Photo by Patricia Mullins and Kristie Reddick)

Another unique structure is a set of special sensory organs on their fourth pair of legs called racket organs, or malleoli that aid in feeling vibrations. It looks like solifuges have ten legs instead of eight like other arachnids, but those front leg-like organs are actually mouthparts called pedipalps! Even though all arachnids have pedipalps, only solifuges have tiny suction cups on the ends, charmingly called suctorial organs. These help them hold onto prey and climb vertical surfaces like plant stems, walls and even glass. Remember, they are climbing these vertical surfaces with mouthparts, so it's like you climbing the side of a building using only your lips! Pretty incredible...

A large male rhagodid from northern Kenya. Count the legs! The front "legs" are actually mouthparts called pedipalps.

These arachnids live in arid, and semi-arid environments all over the world, and are found on all continents except for Australia and Antarctica. In the United States, they range from Texas, west to the high deserts of California and Oregon, and north to Montana. You can find solifuges during the warm summer months in cooler climates and year round as you get closer to the tropics. Not all species live in the desert; one large species has been found in the tropical forests of southeast Asia! Most solifuges live in burrows that range from shallow depressions under rocks to small tunnels 3 feet underground. Females tend to stay with their burrows and defend them, eventually laying eggs. Males will have temporary burrows and usually roam at night hunting prey and searching for females.

Solifuges often dig burrows in the ground for shelter from predators and the hot midday sun. We found this small solifuge in the family Solpugidae under a rock near Lake Baringo, Kenya.

These animals are predators with huge appetites! They mainly eat insects in their size range like crickets, roaches and termites, but some of the larger species have been known to eat small lizards and rodents. They are solitary creatures and will not hesitate to attack and eat each other in an encounter. Some have been reported to eat so much at one time that their abdomens bulge and distend and they are unable to walk until they digest their meal. We have a great picture of this in The Bug Chicks Episode 2: Spider Specifics!

Fun Facts

  • There are about 1200 different species of solifuge in the world, and more are being described all the time.
  • Solifuges are incredibly fast runners! Some have been clocked at over 50 cm/second.
  • They range in body size from a few mm to over 7 cm in length.
  • Males have longer legs and females have thicker bodies.
  • Most are a tannish brown in color, but some species are black and red, and others white and purple!
  • Most solifuges are nocturnal but there are several species in Africa that can only be found running around during the hottest part of the day.

We found this diurnal solifuge on sharp volcanic rocks at the Shetani Lava Flow in Kenya.

I'll be writing a great deal more on solifuges in the future, as I studied them in East Africa for my Masters work in grad school. Look out for posts on solifuge myths, legends and lore! These animals are tragically misunderstood and demonized and I hope to shed some light on their real behaviors and biology in the coming months. In the meantime, check out the great resource site of the NSF Global Inventory and Survey on Solifuges at www.solpugid.com.

Please also feel free to share any stories, anecdotes or questions you may have regarding these fascinating creatures!

--Kristie

**All images copyright Solpugid Productions and The Bug Chicks

Original post January 24, 2012 can be found on www.thebugchicks.com.

About The Bug Chicks

Kristie Reddick and Jessica Honaker are The Bug Chicks. They each have Masters Degrees in Entomology and love to teach people about insects and spiders.

The views expressed are those of the author and are not necessarily those of Science Friday.

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