Category Archives: Spiders

The Puppy Spider Is Not As Big As You Think

by

While we’re on spider debunkings, Piotr Naskrecki’s “puppy spider” story is making the media rounds this week, spawning the usual juvenile Nopes and Kill It With Fires! With every re-telling the spider gets bigger, of course.

Not to rain on the Goliath spider parade, but what Piotr originally reported was:

they weigh up to 170 g – about as much as a young puppy.”

170 grams is big. By arthropod standards, it’s huge. But the spider is not, say, the Shelob people are imagining. For perspective, I’ve marked 170 grams on a standard puppy growth chart.
 
spider

 

Puppy spider is not a 3 week old Labrador. It’s the weight, at birth, of a Chihuahua. Big, sure, but you’re not going to saddle this thing up and ride it to work.

The spider looks huge in the photographs for another reason, too. Piotr used wide-angle lenses that exaggerate the size of foreground relative to background objects. This wide-angle macro effect is a technique that Piotr does especially well. And it makes big spiders look larger than life.

Anyway, if you’d like one of Piotr’s puppy spiders for your living room wall, he’s just put a print on sale for prices so low he can’t be making any money:

Photo copyright Piotr Naskrecki, all rights reserved.

 

Three Reasons Why Spiders Can’t Burrow Through Human Skin

by

Australia's redback spider (Latrodectus)

 

Yesterday, you may have seen this amusing-yet-dismal failure of the news media. Hundreds of outlets breathlessly reported a tourist’s tale of a skin spider plowing a pustulated trail through his belly. Snopes dissects why the story is bogus; essentially, the sole source is the tourist himself. The poor kid was likely told he had scabies mites, or similar common affliction, and not knowing what a mite was he settled on the nearest arachnid he recognized. That, plus ingrained cultural arachnophobia and a media disinclined to turn down click revenue over such a silly matter as ethics, and the story goes viral.

Shoddy journalism aside, there is no plausible reason for any spider to burrow into skin, and no physical attributes that would allow them success at it, either. Spiders can’t do it for the same reasons giraffes can’t hover: the laws of physics just don’t work that way, not for the way spiders are built. Here are a few reasons why the story simply could not have happened as reported.

1. Spiders are active animals that need to breathe. That’s hard to do when trapped under skin, and spiders lack the breathing tubes of real skin-burrowers like botfly.

2. Spiders are too delicate. Animals that burrow are strong, compact, and stubby. Think of the bullet-like build and short, powerful legs of a mole or a wombat. Serious burrowers like earthworms lack legs altogether. What’s a spider? Pretty much the opposite. Inconvenient legs everywhere, and far too spindly and weak to burrow. (A few spiders do make soil burrows, but soil is a rather different and more forgiving medium).

3. Spiders lack an implement for opening a suitable entry hole. Spiders have fangs, which are thin and sharp and can appear scary, but if you’ve ever tried to dig a hole using only hypodermic needles you’ll appreciate the uphill battle a spider faces.

Also, there has never been a single confirmed observation of a skin-burrowing spider.

So, no. You don’t have to worry about skin spiders.
 

Sunday Night Movie: Look Deep Into My Eyes

by

This hypnotic clip, taken by JerseyBug, is a glimpse into one of the most fascinating set of eyes among all animals, those of jumping spiders:

The spider’s anterior median eyes (the big ones) focus sharply and can even detect depth, but their abilities are limited by an extremely narrow field of vision. Spiders counteract the narrowness by moving some of the internal elements, allowing the animal to scan more broadly. Thus, the odd color changes in this jumper’s eyes are essentially the spider having a look about.

A Social Spider In North America

by

Anelosimus studiosus

Anelosimus studiosus, adult female (center) with two juveniles.


 
A highlight of my recent excursion to the University of Texas at Austin was learning about some little spiders, Anelosimus studiosus, that spin messy webs in the undergrowth. Remarkably, these spiders are communal. Most arachnids are solitary predators, but Anelosimus studiosus lives and hunts in shared webs. 

These social tendencies render Anelosimus exactly the sort of spider that might lure an ant biologist. And of course, that is how I happened to hear of them. UT’s famous ant-fungus lab, the one headed by Ulrich Mueller, has a student, Emma Dietrich, working on the spiders. Emma was kind enough to collect a few webs from around campus for me to photograph.

Anelosimus studiosus

Mom spider hangs out.


 
Anelosimus studiosus is typically subsocial- meaning that young spiders remain with their mother in the web but disperse at maturity- but populations in colder parts of the range are properly social, with multiple breeding adults sharing webs.

I had always thought of spider sociality as a tropical phenomenon. I observed another species of Anelosimus, for example, on my last trip to Ecuador. But social spiders right here in the temperate zones of the United States? Fantastic!

Anelosimus studiosus

A male Anelosimus studiosus can be identified, like most spiders, by the “boxing gloves”- the enlarged secondary genitalia on the pedipalps.


 


source: Furey, RE. 1998. Two cooperatively social populations of the theridiid spider Anelosimus studiosus in a temperate regionAnimal Behaviour 55, no. 3 (1998): 727-735.

An ant-mimic spider escapes ant attention by being nearly odorless

by

Meet Peckhamia, a charmingly ant-like jumping spider:

Peckhamia3

Peckhamia is a common ant-mimicking jumping spider in North America (photographed in Urbana, Illinois).

Peckhamia avoids being eaten by predators by appearing like an ant rather than a spider. This defense is two-fold. Ants aren’t as palatable as spiders to most general predators, and spider-specialized predators might not recognize Peckhamia as food.

For mimicry to work optimally, though, spiders must inhabit places with plenty of ants. Not the easiest task, since ants eat spiders. And because most ants have poor vision, the spider’s physical resemblance to ants isn’t much help.

So how does this ant mimic spider escape being attacking by ants?

A new paper by Divya Uma et al in PLoS One provides a partial answer: Peckhamia doesn’t smell like a jumping spider. It doesn’t smell like an ant, either, so it’s not a chemical ant mimic. In fact, Peckhamia doesn’t smell like much at all. Look at the results of Uma et al’s cuticular hydrocarbon assay:

Figure 5 from Uma et al 2013, showing that Peckhamia have lower amounts of cuticular hydrocarbons than both the ants they mimic, and non-mimic species of jumping spiders.

Cuticular hydrocarbons are chemicals that impart odor, and Peckhamia has rather low amounts of these. It’s a stealth spider!

The researchers also measured predation rates by spider-eating wasps on Peckhamia (lower than on related species), and rates of attack by ants (lower against mimic spiders than against non-nestmate ants). I’d have liked to see the next step of actually painting hydrocarbons on the mimics to gauge the ants’ reaction, but even without that experiment the odorlessness of Peckhamia is an intriguing observation.

[for more ant mimics, see my ant mimic photo gallery]


source: Uma D, Durkee C, Herzner G, Weiss M (2013) Double Deception: Ant-Mimicking Spiders Elude Both Visually- and Chemically-Oriented Predators. PLoS ONE 8(11): e79660. doi:10.1371/journal.pone.0079660