Tricky spiders' web and 33 new species of trapdoor spider

Cobwebs are actually small feats of engineering.  Polymer scientists at the University of Akron have discovered that the common house spider can tailor the type of adhesive discs it uses to anchor its webs, making them stronger or weaker depending on where the cobwebs are situated and the anticipated movements of its prey.

Webs located up in the air, such as those on ceilings and vertical surfaces, tend to catch flying insects, which are moving at a greater velocity.  So the adhesive used in these is stronger – that way the web doesn’t come loose when it’s struck by an airborne object moving at a high rate of speed.  But when spiders build webs that are located close to the ground, they use less adhesive in the discs.  When an unsuspecting insect wanders into a web, the anchoring thread snaps away from the ground and – voila! – the spider’s dinner is left dangling helplessly in the air by a sticky silk strand.

The polymer experts were impressed by the sophistication of this trick.  “What we have also discovered is a key design principle,” said Ph.D graduate Vasav Sahni. “It’s not a question of the inherent chemistry of the glue, but how the same glue can have different degrees of adhesion.”

The Akron team have published the details of their study in the most recent issue of Nature Communications.

The discovery of 33 new species of sneaky trapdoor spiders boosts the total number described in one genus from seven species to 40.

Trapdoor spiders, which belong to the same suborder as tarantulas, are pretty badass. Instead of weaving webs, they build subterranean silk-lined burrows — and cap the burrow with a trapdoor. Then, hunkered down beneath the trap door, the spiders wait for an unsuspecting insect to trigger the trip lines.

“They’re sort of ambush predators,” said arachnologist Jason Bond, director of the Auburn University Museum of Natural History, and author of the study describing the new species, which appeared Dec. 19 in the journal ZooKeys. “They wait at burrow entrances at night, until some dull-witted insect comes over. Then they jump out, bite it, and take it to their burrow. This particular group, they pack its carcass down into the bottom of the burrow.”

Some of the newcomers have pretty fantastic names. Aptostichus barackobamai is named for Barack Obama. Aptostichus bonoi, which lives in Joshua Tree National Park, is named after U2 band member Bono. Aptostichus sarlacc? That’s basically the Tatooine spider. It lives in the Southern California desert, and takes its name from Boba Fett’s ground-dwelling tormentor. The Atomic Penn Jillette Trapdoor spider (Aptostichus pennjillettei) is from the old nuclear testing site near Mercury, Nevada.

Male Aptostichus barackobamai. Image: Jason Bond.

Female Aptostichus barackobamai. Image: Jason Bond.

Female Aptostichus aguacaliente. Image: Jason Bond.

Female Aptostichus atomarius. Image: Jason Bond.

Female Aptostichus chavezi. Image: Jason Bond.

Male Aptostichus miwok. Image: Jason Bond.

Female Aptostichus stephencolberti. Image: Jason Bond.

Trapdoor spider burrow, closed. Image: Jason Bond.

Trapdoor spider burrow, open. Image: Jason Bond.

One of the species in this newest batch, found near a relatively young, volcanic cinder cone close to Barstow, CA, is named after Bond’s daughter, Elisabeth. Living among the lava tubes that extend from the cone, Aptostichus elisabethae builds deep, elaborate burrows that extend multiple feet into the ground. Some of the other species burrow only a few centimeters beneath the surface. “I’ve always appreciated their engineering marvels,” Bond said, noting that the spiders continually reinforce their burrow walls with silk, and that some desert species maintain a routine of “winter cleaning,” leaving little piles of excavated material outside.