Nights of the Living Dead… Further Horrors of the Insect World

(By: Paul Nylander Via: The Tucson Citizen)

Common Name: The Tarantula Hawk

A.K.A.: Genera Pepsis and Hemipepsis

Vital Stats:

  • The two genera make up Tribe Pepsini in Family Pompilidae
  • Grow up to 5cm (2”) long
  • Stingers are up to 7mm (1/3”) long
  • Quite long lived for wasps, with lifespans of more than a year
  • Adults feed primarily on milkweed nectar

Found: Across much of the tropics and southern hemisphere

It Does What?!

Happy Halloween, readers! Today’s the day when we’re surrounded by images of zombies, witches, ghosts, and spiders- all creatures meant to scare us on some level. Of course, only one of these things is real. And spiders truly are a scary thing for many people. For all you arachnophobes out there who are feeling vaguely uncomfortable about the preponderance of fake spiders out there today, did you ever wonder what the spiders fear? What keeps tarantulas, the biggest, scariest arachnids of them all, awake at night? Tarantula hawks, that’s what. If spiders had Halloween, this is what they would dress up as.

A creature that can kill small rodents being outmatched by a nectar-sipping insect. Sad.
(Via: Wikimedia Commons)

Like any good mother, the female tarantula hawk wants to ensure that her baby has all the food it requires to grow up into a healthy adult wasp. Rather than bag a large piece of prey and have it spoil by the time her egg hatches, she has developed an ingenious system of keeping meat fresh.

Spying a tarantula from the air, she will attack, injecting the spider with her venom as it struggles to bite her. A particularly hard and slippery exoskeleton renders this counterattack ineffective; the fangs simply slip off her. Before long, the tarantula has succumbed to her venom and is alive, but completely paralysed. Once the prey has been neutralised, she sets out over land, dragging the spider up to 100m (quite a long way, considering the scale involved) back to the site of a burrow she has dug out. Here, our mom-to-be lays a single egg on the helpless spider’s abdomen, then proceeds to immure it in the burrow.

A hundred metres starts to look like a very long trip.
(By: Erin Zimmerman, taken during my field work in Guyana)

But this is only the beginning of the horror for the paralysed spider. Soon after, the egg hatches, and the hungry larva tunnels directly into the spider’s flesh, eating as it goes. The larva instinctively knows to avoid the tarantula’s vital organs as it eats, thereby keeping the prey alive for as long as possible. After several weeks of chowing down, the larva finishes off the job and emerges from the spider’s body, having now matured into a wasp. It then simply unseals the burrow and flies away, leaving the late tarantula in its ready-made grave.

Wondering what happens when a person gets stung by one of these? It’s an interesting question, because the answer is both “a lot” and “not much”. You see, the paralytic agent in the venom only works on invertebrates, and won’t actually do any real damage to human tissue. Before you go trying to catch one, though, know that, in terms of immediate reaction, tarantula hawks are considered to have the single most painful insect sting in the world. It’s best described by an entomologist who has actually experienced such a sting:

“Advice I have given in speaking engagements was to ‘lay down and scream’. The reasoning being that the pain is so debilitating and excruciating that the victim is at risk of further injury by tripping in a hole or over an object in the path and falling onto a cactus or into a barbed wire fence. Such is the pain, that few, if any, can maintain normal coordination or cognitive control to prevent accidental injury. Screaming is a satisfying expression that helps reduce attention to the pain of the sting itself.” [Schmidt 2004]

In short… don’t touch these.

A few words now on just how frighteningly well-adapted this wasp is. Not only is it covered in armour and full of incredibly painful venom, but at roughly the size of your little finger, it’s one of the largest wasps out there, and more of a fight than most insectivores want to deal with. It is essentially without predators. And lest any potential enemies forget why they’re not touching it, the tarantula hawk has both a distinct colour and a characteristic odour, meant to remind aggressors of the pain associated with any previous run-ins. Researchers have described tarantula hawks as being “among the best defended animals on earth” [Schmidt 2004]. And because success always spawns imitation, there are now several other creatures mimicking the appearance of the female tarantula hawk as a form of protection, including the more-or-less defenceless males of the same species.

So the next time you shudder at the thought of a tarantula stalking you in the wild, stop and remember what might be stalking it.

[Fun Fact: Despite its phenomenal pain-inducing qualities, tarantula hawk venom is only about 5% as lethal as honeybee venom, based on studies by people who inject white mice with horrible things for a living.]

Says Who?

  • Alcock & Kemp (2006) Ethology 112: 691-698
  • Kurczewski (2010) Northeastern Naturalist 17(1): 115-124
  • Schmidt (2004) Journal of the Kansas Entomological Society 77(4): 402-413
  • Schoeters et al. (1997) Canadian Journal of Zoology 75: 1014-1019
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Death from Below! (The Purse-Web Spider)

(Via: Wikimedia Commons)

Common Name: Purse-Web Spiders

A.K.A.: Family Atypidae

Vital Stats:

  • The family contains three genera; Atypus, Calommata, and Sphodros
  • Females reach up to 30mm (1.2”) in length
  • Fangs can measure up to half the spider’s body length
  • Prey includes crickets, beetles, millipedes, ants, wasps, and other spiders
  • Web tubes measure up to half a metre (20”) from top to bottom

Found: Africa, temperate regions of North America, Europe, and Asia

It Does What?!

Imagine you’re a beetle, peacefully strolling along the forest floor, minding your own business, when suddenly, two enormous black spikes drive up out of the earth and impale you through the abdomen. As everything fades to black, your last beetle-ly thought is, “What the hell was that?!

You have just become a tasty lunch for the purse-web spider.

So how does this work? Well, unlike most of the spiders we’re familiar with – those with small, pincer-like mouths that sit in webs all day – purse-webs are a type of primitive spider called a mygalomorph. In this group, the fangs are like a pair of large (relative to the spider) tusks that only move up and down; they don’t pinch, and this feature lends itself to some rather creative hunting methods.

Rather than constructing a flat, aerial web designed to have something fall into it, the purse-web spider spins what is essentially a silken tube-sock. The ‘foot’ of this sock lies along a slight depression in the ground, while the upper part lies vertically against a tree or rock (or, in some species, angles downward into the earth). The spider will then place bits of bark and lichen onto both parts of the web as camouflage. Over time, moss will actually begin to grow on the web, completing the disguise. All the spider needs to do now is wait, suspended from the ceiling of her underground lair, for some unwitting creature to walk over it. When this happens, she rushes to the source of the disturbance and spears her prey from below with her fangs before they realise what hit them (like this).

Invisible by spider standards, anyway.
(Via: Wikimedia Commons)

The spider will be vulnerable to larger predators if she ventures out into the open, so she simply cuts a slit in the web, drags her impaled prey inside, and seals up the hole again. Having sucked out their delicious insides, she then drops the dead husks out of the top of her sock like so much household garbage. In fact, researchers determined the diet of the purse-web spider by noting the various exoskeletons hanging from the outside of the web, having gotten caught on their way down. Apparently, all the dead bodies seemingly stuck to the side of a nearby tree aren’t much of a deterrent to other passersby.

So, since these spiders never leave their burrows, and kill anything that approaches, mating must be tricky, right? Right. The male is attracted to the female’s web by means of pheromones, and ventures out to find it. Once he locates the web, he must be very careful, tapping at the outside of the tube in a way that indicates he isn’t prey. Ultimately, though, whether he’s prey or not will be up to her. If the female inside isn’t yet mature or is already pregnant, she won’t hesitate to eat him when he attempts to enter the burrow. Researchers experimenting with placing male spiders in or near the webs of unreceptive females noted, essentially, that they run like hell as soon as they figure out what’s what. Research is amusing sometimes.

A male purse-web spider on what will be either the best or worst day of his life.
(Via: Florida Backyard Spiders)

But in the happy instances where the female is willing to mate, the male enters safely, and in fact continues to live with her for several months of domestic bliss before he dies naturally. And then she eats him anyway. Spiders are not sentimental creatures. Her eggs will take almost a year to hatch, and the young will stay with her for nearly another year after that, before striking out in the world to spin their own tube-sock of death.

Says Who?

  • Beatty (1986) Journal of Arachnology 14(1): 130-132
  • Coyle & Shear (1981) Journal of Arachnology 9: 317-326
  • Piper (2007) Extraordinary Animals: an encyclopedia of curious and unusual animals. Greenwood Press, Westport CT.
  • Schwendinger (1990) Zoologica Scripta 19(3): 353-366

Every Day is a Crappy Day for the Bird-Dropping Spider (Celaenia excavata)

Celaenia excavata
(via: http://commons.wikimedia.org/wiki)

Common Name: The Bird-dropping Spider

A.K.A.: Celaenia excavata

Found: Eastern and Southern Coastal Australia

It Does What?!

Quick, what’s the first thing that comes to your mind when someone says “disgustingly inedible” ?

If you said “Why, poop, of course!”… congratulations, you think just like Celaenia excavata. And if the thing you’re trying to look inedible to is a bird, naturally, you go with bird poop. Such is the evolutionary reasoning behind the politely-named Bird-Dropping Spider. And while remaining motionless is a must, looking the way it does allows the spider to sit comfortably atop a leaf all day, secure in the knowledge that spiders’ main predators, birds and wasps (who apparently aren’t into eating bird poop either), won’t take an interest.

“Nobody here but us droppings.”
(Thanks to Ron Atkinson at http://www.findaspider.org.au)

But the mimicry doesn’t end there for this sneaky little guy- by day it sits inactive and gross-looking, but by night, it hangs upside down from a leaf and releases the mating pheromones of a female moth. When some unlucky male moth comes looking for a good time, the spider snatches it right out of the air with its powerful front legs and wraps it up for dinner. The moth may be eaten right away or, if its capturer isn’t feeling hungry quite yet, be hung under a leaf next to the spider’s egg sacs, which, oddly enough, look like nuts (see top photo).

Believe it or not, Celaenia excavata isn’t the only spider out there masquerading as merde. Another such trickster is Mastophora cornigera, a North American species which is part of a group known as the Bolas Spiders, or Fishing Spiders. Not content to hope their prey wanders into arm’s reach, bolas spiders release pheromones to attract male moths, then dangle a line of silk with a sticky blob on the end. Once a moth gets close enough, the spider swings its line and –yoink– rips the poor thing right out of mid-air. Whoever thought up Spiderman’s web-slinger clearly had a bolas spider in mind.

So there you have it, the leisurely lifestyle of a successful spider: pile of poo by day, upside-down fisherman by night.

Says Who?