For the past several weeks we have escaped dreary chilly weather in Maryland and traveled thousands of miles south to tropical rainforests in Central America. We met other-worldly amblypygids, colossal katydids, and hyper-vigilant paper wasps. This week we return to a muddy trail on the Osa peninsula in Costa Rica and make a quick stop near the ancient Mayan city state of Xunantunich in Belize to visit some very large spiders.
Near the lair of the spooky whip spider we met a few weeks ago we came across a gnarly old tree with several irregular fissures in its trunk. In one fissure we spied the legs of a gorgeous tarantula apparently just waiting for a couple of bug geeks to come along and tease it with the mid-vein of a decomposed leaf. While never fully exposing herself, we did have a few moments to enjoy a glimpse of this beautiful orange mouth tarantula. A few hundred miles further north along the Mopan River in Belize a similar nocturnal adventure revealed a beautiful juvenile redrump tarantula strolling along the grassy riverbank. Despite its inherent shyness, the spider did pose for a few moments on a hand to give us a closer look.
Even enticement with a faux prey item wasn’t enough to convince this beautiful orange mouth tarantula to leave the safety of her lair in a hollow tree.
Much lore and misinformation surrounds these fascinating predators. Tarantulas are named after Taranto, a city in southeastern Italy on the Ionian Sea. In the 15th through 17th centuries, legends told of the fearsome bite of the Italian tarantula that caused a condition known as tarantism. Tarantism was manifested by heightened excitability, restlessness, and sometimes an irresistible urge to dash about. Legend had it that the disease could only be cured by listening to lively frenetic music, called the Tarantella, or by engaging in a frenzied whirling dance that could last several days. Yikes! Talk about Saturday night fever. The culprit behind this mischief was actually a wolf spider, Lycosa tarantula, locally known as a tarantula. Wolf spiders belong to a family known as Lycosidae.
True tarantulas such as the ones we encountered in Costa Rica and Belize belong to a family of large hairy spiders know as Theraphosidae. These unusually large spiders sometimes measure almost a foot from tip to tip of their extended legs. They have remarkable longevity and can live in excess of thirty years. Their bite is memorable by virtue of some very large fangs hidden beneath the head of the spider. Some species of Psalmopoeus produce potent venom chemically related to the active ingredient capsaicin, the chemical that puts the zing in chili peppers. Tarantulas are primarily nocturnal hunters of insects, other spiders, and small reptiles. However, some of the larger and more agile species have potent venom used to help immobilize small mammals and birds. After catching their victim with stealth or speed, they grind it into a ball, secrete digestive enzymes into the pulpy mass, and suck the liquefied contents into their mouth.
Tarantulas have one of the most interesting mating rituals of any animal in the rainforest. The male tarantula is much smaller than his mate and to successfully sire a brood of young, he places his life at risk in the presence of a potentially hungry female. To complete his task, the male tarantula constructs a thin web on which he deposits sperm. Small leg-like appendages called pedipalps located near his jaws are used to pick up the sperm and carry it about. When he encounters a potential mate, he busts his best moves which may include drumming, waggling of legs, and other gambols. This dance helps his mate recognize her suitor as a member of the same species. We all know how disagreeable it is to misidentify members of another species when we are searching for a mate. With the preliminary introductions out of the way, the male warily approaches the female and does his best not to get eaten. The male tarantula is equipped with special claws on his front legs that help him grasp the female, while he uses his pedipalps to carefully place sperm into a pouch on her underside. Sometimes the male escapes this romantic encounter, but sometimes he does not and becomes dinner instead.
While out for a nighttime stroll in the grass, this shy juvenile redrump tarantula was surprised to be handled by curious humans.
The female tarantula lays several hundred eggs in a silken ball. These eggs are stored in a burrow and tended until they hatch. These large juicy arthropods would seem like a tempting meal for other predators in the jungle. However, in addition to sharp fangs, the tarantula has another potent defense. The abdomen of many species of tarantula is covered with a dense coat of hairs known as urticating hairs. When the human encounter became just a little too unsettling, the spider raised its abdomen and expelled hairs by rubbing them off with the hind legs. These irritating hairs can lodge in the eyes or nasal passages of a would-be predator and thereby thwart an attack.
On several visits to Central American rainforests we have encountered tarantulas, enjoyed their company, and returned them to their galleries. However, due to habitat destruction and collecting for the pet- trade industry, tarantulas in the genus Brachypelma have become threatened and are now protected by the Convention on International Trade in Endangered Species of Wild Fauna and Flora laws. These regulations prohibit the international trade of more than 34,000 species of wild animals and plants to prevent their extinction.
In the light of day, one redrump spider had a chance to examine a lucky student.
Bug of the Week gives special thanks to Carlos and the other nocturnal adventurers at Aguila de Osa who were the inspiration for this episode. We thank the hearty crew of BSCI 339M: Tropical Biology in Belize who spied a redrump tarantula in the grass and extracted another from its hole to enjoy a close encounter of the arachnid kind. Much of the information for this Bug of the Week came from Jerry G. Well's delightful book "The Guide to Owning a Tarantula."
We are indebted to globetrotting Guy Tansley for assistance in identifying our tarantulas. Visit his amazing web site to learn more about fascinating wildlife in exotic locations around the world at: https://www.bugsnstuff.com/guy-s-research-trips/costa-rica/