How Many Spiders?

I’ve been sick for a few days now, so I haven’t put any real time into the “what are these fossils” article I promised last time. Instead, let’s look at something comparatively simple. I picked up my son from Kindergarten yesterday. Normally, since I was home and it’s only about a quarter mile, we’d have walked. But, like I said, I’ve been sick. So he’s in the back seat excitedly telling me about his Valentine’s Day party. “Dad?” he asks as we pull into our garage.

“Yes, son?” I respond.

“How many spiders can you carry?”

No, I have no idea where that came from. But I’ve gotten used to that by now. “Well,” I say, “that depends on how big they are, and how cooperative they are.”

So, how many could you carry?

“I could carry a hundred spiders!” he declares.

“Maybe,” I tell him. “If you could put them in a box. Or if they were tiny and well-trained.”

So, how many could you carry? Like I said, it depends on the spider. The good people at Guinness World Records say the Patu marplesi is the smallest spider, while Wikipedia contradicts them and states that a related species – the Patu digua is the smallest. Either way, it’s a tiny spider – the body size is only 0.37 mm – and the author of Catalog of Organisms states that “If one of these spiders crawled into your ear while you were sleeping, it could probably slip into your Eustachian tubes and tap on the back of your eyeballs.” So try not to think too hard about that.

patu-digua

“Peek-a-boo!”

I couldn’t find anything at all about how much (little?) this critter weighs. So, I’m going to run the risk of estimating. Here’s what I did, so that you can play the home game. I found an article titled “Estimating Live Spider Weight Using Preserved Specimens” from The Journal of Arachnology in 1996. It provides a formula for calculating weight from length for spiders: ln weight = 1.844 + 2.711(ln length), and seems to indicate that the weight is read in milligrams (mg) and the length in millimeters (mm). So, that would give us ln weight = -1.844 + 2.711(ln 0.37). That works out to… let’s see…

  1. ln weight = -1.844 + 2.711(ln 0.37)
  2. ln weight = -1.844 + -2.695
  3. ln weight = -4.539
  4. e^ln weight = e^-4.539
  5. weight = 0.010684 mg

So, one 0.37 mm spider appears to weigh 0.01 mg. How many of these could we move? Let’s find out?

Bare Hands

My palm is, roughly speaking, a 9 cm by 9 cm (90 mm by 90 mm) square. That gives me 8,100 mm of surface area, so I could stack a single layer of 8,100/0.37 = 21,891 well behaved Patu digua on one hand. Using both hands, I could carry 43,782 of them. The two-hand load would come out to 0.43782 grams, or 0.0015 ounces of spider.

Let’s try and do more. If I cup my hands, I get a sort of rounded cone that’s 7 cm (70 mm) in diameter by 7 cm (70 mm) deep. That gives me a volume of 359,189 cubic mm. Now, let’s assume that the Patu digua takes up the same volume as a sphere 0.37 mm in diameter. That’s 0.212175 cubic mm. So, in my cupped hands, I could carry 359,189/0.212175 = 1,692,890 Patu digua. Those guys would weigh in at 18.0868 grams (0.63799 ounces).

We’re not savages, you know

Yes, I know. So let’s fill a box. A standard U-Haul shipping box is 41.5″ (1054.1 mm) x 38.5″ (977.9 mm) x 18.75″ (476.25), for a volume of 429,072,327.3375 cubic mm. That means I could carry 429,072,327.3375/0.212175 = 202,256,756 of the little spiders – 21.606 kg (47.6 pounds) of Patu digua. My son weighs more than that, so I know for a fact that I could easily carry that box of spiders from my house to my car, and then from the car to the Post Office, and then from the Post Office back to my car because the USPS would most likely refuse to accept that package.

Cool. What about big spiders?

National Geographic informs me that the South African Goliath Birdeater Tarantula is the biggest spider in the world as measured by body size. Nothing I could find gave me an explicit size, but terms like “puppy sized” and “the size of a dinner plate” were bandied about with distressing familiarity. National Geographic also states that:

Many of the locals in northeastern South America regard T. blondi as a tasty snack. They first singe off the urticating hairs, then wrap the spider in banana leaves to roast it. Tarantula expert Rick West, who once sat down for a meal of these spiders with the local Piaroa people of Amazonas in Venezuela, says T. blondi can be surprisingly tasty and moist. (Also see “UN Urges Eating Insects; 8 Popular Bugs to Try.”)

“The white muscle ‘meat’ tastes like smoky prawns, while the gooey abdominal contents is hard-boiled in a rolled leaf and tastes gritty and bitter,” West says. “The three-quarter-inch [two-centimeter] fangs are used after the meal as toothpicks to remove T. blondi exocuticle from between one’s teeth.”

goliath

“I’m tasty!”

On the other hand, if you’re measuring by legspan the prize goes to the giant huntsman spider, with a leg span over one foot (30.48 cm) across. No word on how they taste, though.

huntsman

“Come on and have a go, if you think you’re hard enough!”

Without specifics, I can’t tell you how many I could handle. One per hand, maybe, and maybe four in a shipping crate. But, on the other hand?  Oh my god no.

Advertisements