8 July 2020

With COVID-19 raging around the world, we humans feel a little less invincible that we did a few months ago. Despite our own fragility there’s a tiny creature, less than 1mm long, that has survived all five mass extinctions. The tardigrade or water bear is practically indestructible.

Tardigrades have a second nickname — moss piglets — because moss and lichen are their favored habitat. Tardigrades don’t care how cold it is. They live in glacier mice and …

… a lot of harsh locations as shown in the video below.

Tardigrades’ only weakness seems to be prolonged heat, so climate change may be bad for them in some places on Earth. However, they’re so versatile and widespread I think most will survive. They are tough little water bears.

p.s. If you missed the blog post on glacier mice, click here to catch up.

(water bear screenshot from the Dodo video above; glacier mouse by cariberry via Flickr)

Now that it’s spring and we’re at home all the time we see indoor wildlife, especially at night. Don’t be afraid when you turn on the light and encounter this startling arthropod. The house centipede is hunting down your enemies.

House centipedes (Scutigera coleoptrata) are nocturnal raptors, the owls of the bug world.  They eat a wide variety of live prey including spiders, flies, moths, silverfish, ants, termites, roaches and bedbugs which they catch by running them down.

With so many of our enemies on the menu, you’d think we’d be grateful to have them in the house. Unfortunately house centipedes look creepy, move way too fast, and then pause long enough for us to smash them … or for a cat to touch one as Jlauboro‘s cat did in 2009.

However, they have some fascinating qualities. Here are just a few as described on Kelly Brenner’s blog and at Animal Diversity Web.

• House centipedes (Scutigera coleoptrata) have only 30 legs, arranged in 15 pairs.
• They’re the world’s fastest arthropod at 16 inches/second.
• The first pair of legs are mouthparts that deliver poison to kill their prey.
• Centipedes groom themselves after they eat, cleaning each leg in turn.
• They’re nocturnal and prefer damp places because they don’t have wax on their exoskeltons and would otherwise dry out. That’s why you sometimes find one in the sink.
• House centipedes have sex somewhat remotely. When a male finds a receptive female he spins a silk pouch on which he deposits his sperm. She picks up the pouch and fertilizes her eggs.
• The females are active mothers, protecting their eggs and staying with their young for about two weeks after hatching.
• Young centipedes are tiny (and kind of cute). Born with only 8 legs, they gain new legs when they grow new segments at each instar.

House centipedes can live their entire lives indoors, providing us with watchable wildlife if we can bear to look at them.

Learn more about house centipedes at On Being Misunderstood.

(photos from Wikimedia Commons; click on the captions to see the originals)

Insects have many techniques for escaping predators. They fly, sting, use camouflage, or contain poisons. The Indian stick insect (Carausius morosus) has none of these skills so it plays dead.

John Skelhorn at Newcastle University wondered if feigning death actually works. Stick insects taste good when they’re alive but taste terrible when dead. Do predators always avoid dead-looking critters? Skelhorn experimented with stick insects and one of their predators to find out.

First, here’s what a living stick insect looks like.

For predators, Skelhorn chose chickens who’d never seen a stick insect — 90 chicken chicks divided into three test groups.

Naive chicks who’d never eaten a dead stick insect were willing to approach those playing dead. However, any chick that had tasted a dead one, moved back and refused to touch the pretender. (Eeeeww! They wiped their beaks.)

Does an insect playing dead live longer? Yes, if the predators have experience.

Read more at Scientific American The Art of Playing Dead and the original study published in Current Biology.

(photos from Wikimedia Commons; click on the captions to see the originals)

On Friday we watched gulls charming the worms. Today we’ll watch people do it.

Perhaps you’ve noticed that earthworms come out on the sidewalks when it rains. They rise to the surface in damp soil when they hear the pattering of rain above them. Gulls and wood turtles take advantage of this by tapping on damp ground to lure worms to be eaten.

People use a variety of techniques, called worm charming, to collect worms for fish bait. The video above was taken at the annual World Worm Charming Championships in Willaston, UK.

Below, a man and wife gather worms for the fish-bait trade in Florida. With his tools he makes a noise called worm grunting while she gathers the worms.

(videos from YouTube and Wikimedia Commons)

Ants are amazingly strong for their size, able to lift objects 5,000 times their own body weight and carry them back to the nest. If an object is too big to lift, the ant drags it all the way home.

We’re often so mesmerized by the ant’s struggle that we forget she has an additional challenge. She has to navigate while walking backward. Ethologists at Paul Sabatier University wondered how ants do this so they baked some cookies and ran some tests.

Using a nest of Spanish desert ants (Cataglyphis velox) the scientists laid out large cookie pieces for the ants to find. Without disturbing the ants’ paths scientists noted how often they turned around to check their bearings. They also “airlifted” some ants away from the nest (no path to remember) and messed up the scenery for others so the path would look different.

To give you an idea how hard this is, imagine walking backward without the help of handheld Google/Apple maps. How often would you turn around to check where you were going? And what would you do if an enormous hand rearranged the scenery and nothing looked the same?

Some of the confused ants never made it, but those who knew their path walked 6 meters without peeking. This is equivalent to a human walking backward without peeking for the length of two football fields.

Perhaps it helps that ants can see nearly 360 degrees around their heads. Despite all the challenges they still get home.

Read more in Science Magazine.

p.s. Desert ants don’t use pheromone trails to navigate. Instead they use many other tools including sight, body memory, the Earth’s magnetic field and the scents of other things.

(photo by adrianalexalexander via Flickr, Creative Commons license. Video from Wikimedia Commons; click on the captions to see the originals)