Tentworms on a choke cherry branch, 18 April 2015 (photo by Kate St. John)
In a normal spring tent caterpillars would have constructed gauzy tents in the cherry trees just before the leaves unfurled. This year I haven’t seen any tent caterpillars and we’re already at “Full Leaf”(*) in Schenley Park. Did our unusually cold spring kill them?
The absence of tent caterpillars affects birds, especially yellow-billed and black-billed cuckoos who rely on them as a food staple. Perhaps the absence of tent caterpillars explains why cuckoos are scarce this year.
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.
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.
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.
As human population soars and fish populations plummet illegal fishing has ramped up in the world’s oceans. With 50% of the world’s fish population now gone, countries protect fish within their 200-mile Exclusive Economic Zones (EEZ) but dishonest fishing vessels sneak in to capture endangered species and overfish what’s left.
Catching the perpetrators, or even knowing they’re out there, has been quite difficult despite the ability to track them by satellite. That’s because dishonest vessels turn off their Automatic Identification System (AIS) satellite transponders so they can’t be seen. The boats travel safely without AIS; they use radar to avoid collisions and find fish.
In 2017 Henri Weimerskirch and colleagues at Centre of Biological Studies Chizé launched an innovative study to uncover the extent of illegal fishing. They equipped wandering albatrosses (Diomedea exulans) with radar detectors that transmit location data to satellites. The research team then matches albatross radar sightings to AIS satellite sightings. If there’s a radar ping but no AIS, the boat is operating illegally.
The research team expanded the study in 2019 by fitting 169 albatrosses from Crozet and two other islands with radar detectors (map below). From December 2018 to June 2019 the albatrosses encountered 353 ships, 37% of which had turned off their AIS.
After a 6-month study with the large seabirds, the researchers estimate that more than one-third of vessels in the southern Indian Ocean are sailing undercover, confirming concerns about illegal or unreported fishing.
Armed with this new data, enforcement can now focus on the hotspots of illegal activity. Ideally it will lead to more arrests like the one pictured below in the North Pacific in 2008.
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.
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.
It was only a matter of time before the highly invasive spotted lanternfly (Lycorma delicatula) made its way to western Pennsylvania but it’s disturbing to learn that it’s so close to Pittsburgh.
On 20 January 2020 the Columbus Dispatch reported that spotted lanternfly egg masses were found at the Norfolk Southern railyard in Conway, PA. They probably arrived by train and are now less than 20 miles from Downtown Pittsburgh and even closer to Ohio.
At this time of year the adult bugs are not active so an egg mass, pictured below, is the only thing they found. The authorities scraped away the egg masses and killed the eggs.
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.
Though this arctic seabird doesn’t eat algae it will starve if marine algae is not abundant. On Throw Back Thursday we’ll learn more with the help of two vintage articles.
Dovekies eat small invertebrates and fish but the majority of their diet is made up of copepods. A single dovekie eats 60,000 of them per day. Quadrillions(*) fall prey to dovekies during the breeding season. So … What the heck is a copepod?
Copepods eat microscopic marine algae called phytoplankton that contain chlorophyll and need sunlight to live and grow. In the high arctic, the summer sun makes phytoplankton bloom, as seen below in the Barents Sea. It takes quadrillions phytoplankton to feed billions of copepods to feed the dovekies.
Phytoplankton is really tiny, so small that you need an electron microscope to see it. The Barents Sea bloom above is thought to be Emiliana huxleyi, shown below. The disks are made of calcium carbonate which is also the primary component of seashells. The calcium in phytoplankton makes its way up the food chain.
Thus if phytoplankton is scarce, copepods are scarce and the dovekies starve. That’s how a seabird relies on algae.
(photos from Wikimedia Commons; click on the captions to see the originals)
(*) How many copepods? Here’s a back of the napkin calculation: Suppose there are 50 million dovekies, each one eating 60,000 copepods/day. Dovekies live in their breeding range for four to six months, so there have to be quadrillions of copepods available during that period. Dovekies aren’t the only animal that eats copepods. The numbers are staggering! (My original calculation had a power-of-10 problem. See Tom Brown’s correction.)
Larger than life, a western conifer-seed bug in Pittsburgh, 30 Oct 2019 (photo by Kate St. John)
Insects that disappeared in the cold came out again during last week’s warm weather. On Wednesday I found a western conifer-seed bug on my front porch.
Formerly restricted to the western U.S., the western conifer-seed bug (Leptoglossus occidentalis, WCSB) has spread across North America, to Europe and South America. At 1/2 to 3/4 inches this “true bug” sucks the sap of developing pine cones and the pulp of pine seeds.
The view from Fort Hill at Cape Cod, 18 Oct 2019 (photo by Kate St. John)
Travel is a tonic for seeing the world in new ways. This month my husband and I spent a week with his sister at Cape Cod where we had new weather, new scenery and new looks at plants I might have seen at home.
Our timing was pretty good. We missed the October 12 nor’easter but were on hand for the October 17 “bomb cyclone.” We didn’t lose power, but it was still very windy on the 18th when I visited Fort Hill, pictured above.
Birds were hard to find that day so I noticed plants such as this European spindle-tree (Euonymous europaeus) with puffy, pink, four-sided fruits.
European spindle-tree fruits, 18 Oct 2019, Dennis, MA (photo by Kate St. John)
The puffballs are actually a casing that holds orange fruit within. This ornamental has probably been planted in Pittsburgh, though I’ve never noticed it.
Someone ate this, Cape Cod, 20 Oct 2019 (photo by Kate St. John)
Who ate it? Perhaps this caterpillar did. I found him elsewhere on the plant.
And finally, the sun touched translucent red berries and made them glow at Bell’s Neck.
The small plants have a single leaf midway up the stem (lefthand photo) and were growing among pine needles. Please leave a comment to tell me what they are.
p.s. Thank you to Kerry Givens who identified the red berries as a Canada mayflower and the caterpillar as a Turbulent Phosphila moth.
(photos by Kate St. John except where noted in the captions; click the captions to see the originals)
