How male spiders keep females to themselves

Dwarf spiders don’t need to take paternity tests to know who the father is—for the most part. Right after copulation, males plug up the genital tract of females (red box in picture) to ensure that competitors can’t deposit sperm. Researchers studying the technique found that the larger the plug, the more difficult it is for subsequent males to remove. Described this month in Behavioral Ecology and Sociobiology, the “stoppers” effectively prevent 67.5% of males who show up later from breeding.

Thanks to Dr. Rajadhyaksha for bringing this to the attention of the It’s Interesting community.

Dolomedes tenebrosus spider dies from sex


For the male dark fishing spider, the price of love is death. New research shows that the male Dolomedes tenebrosus (right) expires just after the height of passion, despite no visible assault by his partner. Scientists collected the common U.S. arachnids (see image) in Nebraska parks and did a little matchmaking. In 25 observed matings, after the male stuffed his sperm into the female’s body using his antennalike pedipalp, he immediately went limp and his legs curled underneath him, researchers report online today in Biology Letters. By counting the pulse rate in the spiders’ abdomens, researchers measured the heartbeat of motionless males and confirmed that they do indeed die. As if death weren’t sacrifice enough, the scientists found that lovemaking also disfigures the male. In most spiders, part of the male’s pedipalp swells to deliver sperm before shrinking to normal size. In D. tenebrosus, the pedipalp remains enormously enlarged and presumably useless even after the deed is done. Evolutionary theory predicts male monogamy—such as that shown by the dark fishing spider—when females are larger than males. Smaller animals are more likely to survive to mating age than big ones, the thinking goes, making larger females scarcer than smaller males. And that means males must settle for just one inamorata. True to theory, the female dark fishing spider, whose outstretched legs span a human’s palm, outweighs her man 14-to-1.

Thanks to Dr. Rajadhyaksha for bringing this to the attention of the It’s Interesting community.

Spider constructs fake spider to fool enemies


This isn’t a real spider. It’s a decoy spider built from twigs, leaves, debris and dead insects.

Researchers discovered the spider in the Peruvian Amazon, and even though its decoy looks like a medium-sized spider that’s about an inch across, the impressive fake was actually made by a tiny, tricky 5-millimeter spider. That spider behind the curtain is probably, the researchers say, a new species of Cyclosa, a genus known to pull similar stunts. But those creations are relatively un-spider-like–nothing at this level of detail. The smaller builder-spider even moves back and forth, giving the impression that the decoy spider is moving and, in the process, confusing predators into attacking the decoy instead.

9 new species of tarantula discovered in Brazil

Nine new species of colorful, arboreal tarantulas have been discovered in central and eastern Brazil, an area where only seven tarantula species had previously been known. All nine of the newly described species are threatened by habitat loss and potentially by overzealous spider collectors.

As described this week in the open-access journal ZooKeys, the newly discovered species have been named Typhochlaena amma, T. costae, T. curumim, T. paschoali, Pachistopelma bromelicola, Iridopelma katiae, I. marcoi, I. oliveirai and I. vanini. The Typhochlaena genus had last been seen in 1850.

The study of the area’s tarantulas was conducted by Rogério Bertani, a researcher at the Instituto Butantan in Sao Paulo. A previous spider first described by Bertani, Pterinopelma sazimai, was named one of the top 10 new species of 2011. That spider, like many of the new ones he described this week, is also threatened by the exotic pet trade.

As Bertani writes in his 94-page paper, tarantulas—arachnids of the family Theraphosidae—have not been heavily studied to date, “despite their potential importance as top predators in ecological webs, the pet trade and a source of important tools for pharmacological research.” He definitely picked up the slack here, studying specimens from the wild and nine different museums and other institutions in order to measure legs, hairs, eyes, claws and other physical attributes to determine the new species. The analysis also allowed him to re-describe dozens of previously identified tarantula species.

Unfortunately, just about all of the new species Bertani describes appear to be at least threatened, if not endangered. Of the five Typhochlaena species, only 40 specimens have been collected to date. The new Pachistopelma species he describes depend on high-elevation flowering plants called bromeliads, which offer both water and shelter from intense mountain sunlight but are themselves threatened by habitat destruction in some regions. Other species live in the Atlantic rainforest, which has been reduced to just 7 percent of its original size. Most of the species he describes are extremely colorful, and Bertani says this could lead to exploitation by the illegal exotic pet trade.

Bertani says the discovery of these new species shows how little is known about wildlife even in areas like the Brazilian rainforests that have been identified as biodiversity hotspots.


Trogloraptor: new clawed spiders discovered

A cave-dwelling creature named Trogloraptor sounds like the villain of a B horror film, but it’s actually a newly discovered type of spider.

A team of scientists discovered the spindly armed arachnid in caves and old-growth forests of Oregon and California and reported the find today in the journal ZooKeys. Because of its unique evolutionary features, Trogloraptoridae is not just a new species or genus, but a new family of spiders. The name Trogloraptor, meaning “cave robber,” seems a fitting moniker (above).

The spider is about 1.5 inches wide with its legs stretched out, bigger than a half-dollar coin. It was found living in loose strands of web hanging from cave ceilings and under forest debris. It wields a set of lethal-looking claws, but its hunting and fighting behaviors remain to be seen.

Scanning electron micrograph of the claw of the Trogloraptor spider. California Academy of Sciences

It’s probably a close relative of the goblin spiders, Oonopidae, evidence suggests. But its anatomy is a mix of old and new evolutionary features, giving spider scientists food for thought.

Scientists from the California Academy of Sciences, San Diego State University, and citizen scientists from the Western Cave Conservancy all helped discover the spiders. The California Academy of Sciences team led the study to analyze and describe the new arachnid family.

Spider removed from woman’s ear canal

A woman who went to China’s Changsha Central Hospital complaining of itching in the left side of her head was told by doctors that the source of irritation was a spider that had been living inside her ear canalfor five days.

Doctors reportedly used a saline solution to flush out the spider in order to avoid having the spider burrow deeper inside the canal or bite her.

The flushing technique was successful and the woman reportedly wept with gratitude after being told the spider was removed. Doctors say they believe the spider entered the woman’s home while the home was undergoing renovations, and crawled into her ear while she was sleeping.

A report by CNN states that spiders and other bugs are appearing in greater numbers this summer due to warm weather and drought conditions across the U.S.

“All insects are cold-blooded, so in extreme heat they develop quicker, which results in more generations popping up now compared to previous summers,” Jim Fredericks, an entomologist and wildlife ecology expert with the National Pest Management Association, told the network.

Thanks to A.N., R.G., and P.C. for bringing this to the attention of the It’s Interesting community.

Spider Webs Encasing Entire Trees After the 2010 Flood in Pakistan

The unprecedented 2010 flooding in Pakistan resulted in more than a fifth of the country becoming submerged.  As a result, millions of spiders climbed into trees to escape the rising floodwaters. The water took so long to recede that all the vegetation became covered in a thick mass of webbing.

On the bright side, these areas have seen far fewer malaria-spreading mosquitos than would normally be present in areas with so much stagnant water.