12 September 2022

Mainland spiders are found on remote islands 400 miles from the nearest land and have been noted by ships 1,000 miles at sea. How did they get there?

When baby spiders (spiderlings) disperse and when lightweight species really want to go places they wait for a light wind and electrically charged air. When conditions are right they stand on a high exposed spot on extended legs, tip up their back ends, and eject several gossamer threads from their spinnerets.

The silk automatically forms a lightweight triangular shaped parachute and, because its electrical charge matches the ground and is opposite to the air, it’s repelled from below and pulled into the sky. The gossamer parachute rises up and away and drags the spider with it. And he’s off! Flying backwards thanks to static electricity.

This action, called ballooning, can carry an individual spider at least 1,000 miles on a light wind and two to three miles above the earth (10,500-16,000 feet). The spider can stay airborne over open ocean and thus colonize an island.

Not all spiders go ballooning but the species that do, like the trashline orbweaver (Cyclosa turbinata) pictured at top, have quite a wide distribution.

How can you tell that tiny spiders have been flying? When you see lots of spider silk clinging to branches in a light breeze you’ve found the aftermath of a mass ballooning event.

Read more about spider ballooning at Ask Nature: Spiders Fly Riding Electric Current and at Spiders Colonized A Remote Pacific Island By Flying There.

See the original University of Bristol study, July 2018, at Science Direct: “Electric Fields Elicit Ballooning in Spiders”.

(photo credits are in the captions, click on the captions to see the originals)

4 September 2022

Dung beetles coexist with large animals because their entire life cycle depends on the droppings of cattle, elephants and other mammals. When Scarabaeus beetles find a dung pile each one makes a ball and uses its hind legs to roll the ball away from competitors, then buries it in a private location for later consumption. Here a sacred scarab beetle (Scarabaeus sacer) rolls and digs.

To move a dung ball the Scarabaeus beetle travels backwards in a straight line against all obstacles. When the ball rolls off course, the beetle climbs to the top, reorients itself and resumes pushing in the correct direction. This so impressed the Ancient Egyptians that they venerated the sacred dung beetle (Scarabaeus sacer) and carved amulets in its image(*).

How do these beetles navigate?

A 2015 study of South African Scarabaeus lamarcki found that the beetles use the sun’s direction and the variation in the sky’s green and ultraviolet colors like a compass. For example, this S. lamarcki beetle travels in the exact opposite direction when researchers use a mirror to show the bug reflected sunlight.

And a 2019 study found that they also pay attention to the wind when the sun is too high to help. See “(Not only) the wind shows the way.”

Traveling upside down and backwards requires lots of navigational tools.

(*)p.s. Did you know that the sacred dung beetle, Scarabaeus sacer, is the origin of scarab jewelry?

The scarab (kheper) beetle was one of the most popular amulets in ancient Egypt because the insect was a symbol of the sun god Re. … The scarab forms food balls out of fresh dung using its back legs to push the oversized spheres along the ground toward its burrow. The Egyptians equated this process with the sun’s daily cycle across the sky, believing that a giant scarab moved the sun from the eastern horizon to the west each day, making the amulet a potent symbol of rebirth.

— MeTropolitan Museum of Art: Egyptian Art, Scarabs

Millennia later, a scarab jewelry pin from the late 1960’s.

(photos from Wikimedia Commons and Kate St. John; click on the captions to see the originals)

2 September 2022

When we say that a bird has “moth-like flight” do we mean that its wings move like this? Check out Dr. Adrian Smith’s fifteen moths in slow motion flight.

1 wing flap from 15 moth species pic.twitter.com/GE9udTmTUv

— Adrian Smith (@DrAdrianSmith) August 25, 2022

p.s. Polyphemus moth species is shown above. Can you find it in the video?

(photo from Wikimedia Commons, tweet embedded from @DrAdrianSmith)

1 September 2022

There are more than 30,000 beetles in the Scarab family (Scarabaeidae), most of them active only at night.

The Glorious Scarab Beetle (Chrysina gloriosa) pictured at top was hiding underground when gardening unearthed it in its native US range of Arizona, New Mexico, Texas.

Hidden gems include Beyer’s scarab which I saw in southeastern Arizona in 2015, described in this vintage article: Like a Jewel.

In the eastern US we have beautiful scarab beetles in our own backyards.

But we don’t think they’re beautiful because they eat our roses.

Japanese beetles (Popillia japonica) are scarabs.

(photos from Wikimedia Commons, bugguide.net and Kate St. John, click on the captions to see the originals)

25 August 2022

Since moving to the 6th floor of a high-rise two years ago we have had no indoor bugs at all. Then, about a week ago, two extremely small bugs with waists and knobbed antennae showed up on the kitchen floor, standing there just outside the bottom of the stove.

They are not interested in water or sweets but only rarely attracted to a very tiny bit of grain or seed. They never fly. They just walk slowly — so slowly that it’s easy to catch one and put it in a ziploc bag (shown below).

Finding two bugs was a curiosity but a week later finding 20 bugs every morning felt like a problem. I checked inside my food cupboards — no bugs at all — and gave my bug-ziploc to building maintenance who is checking for bugs in adjacent units. I’m not to spray in case there will be a multi-floor solution in the days ahead.

Meanwhile Nature’s solution to tiny bugs ran right up to me.

This morning a house centipede (Scutigera coleoptrata), a top predator of insects, ran toward me across the carpet. I screamed! Then I remembered he would eat those little bugs if I could just catch him alive and carry him to the kitchen.

Catching a centipede on the spur of the moment is very tricky. (They run fast!) I fashioned a piece of paper to enclose him and got him to run onto the paper but time after time he ran out the corners of the trap. Finally I enclosed him, carried him to the kitchen, and let him loose below the stove.

A top predator has been moved into position under the stove. I can hardly wait for the house centipede to eat those mystery bugs!

Learn more about house centipedes in this vintage article.

p.s. No, I did not add a centipede. I just moved one about 20 feet.

And I am wondering… Are the mystery bugs actually sawtoothed grain beetles (Oryzaephilus surinamensis)? If so they arrived in someone’s groceries.

(photos by Kate St. John and from Wikimedia Commons; click on the captions to see the originals)

20 August 2022

Last weekend in Lower Frick Park Charity Kheshgi and I saw thousands of caterpillars and a lot of frass dropping from the trees above the pedestrian bridge over Nine Mile Run (pictured above).

Many insects are specialists, consuming a single plant family or genus during in their larval phase. If you can name the plant the caterpillar is eating, you can narrow down the identity of the bug.

Using that method I tried to name the leaves the caterpillars were skeletonizing (eating habits are another clue!) but most were too damaged to identify. Eventually I found a few intact elm-like leaves.

The photo match for “larvae that skeletonize elm leaves” included an adult form matches the golden yellow mystery beetle I saw this summer in Frick Park. These are larger elm leaf beetles (Monocesta coryli).

The “larger” beetle is a pretty big bug, shown for scale on someone’s hand in this photo by Bill Sweeney embedded from bugguide.net, and its color varies. Click here to see an orange one.

Here’s what it will do next.

There is only one generation per year. Eggs are laid in the spring in “hard yellow crusty” masses of 24 to 58 eggs on the undersides of elm leaves. They hatch in about two weeks.

The newly eclosed larvae are about 3 mm long and greenish-yellow. They are gregarious for three to four days and feed on leaf surfaces before dispersing. The mature larvae crawl down the tree and undergo a wandering phase for a few days before entering the ground, where they remain until pupation the following late winter or early spring. Pupation lasts about a month and adults begin emerging in April. Adults are active from April until early August, with most records from June to July. Both adults and larvae exude an orange, presumably defensive, fluid when disturbed.

— Univ of Florida Entomology: Larger Elm Leaf Beetle

So why are these not caterpillars? Because the larvae of beetles are called “grubs.”

(photos from bugwood, from bugguide and by Kate St. John, click on the captions to see the originals)