17 July 2022

Have you noticed small white caterpillars this month, suspended on invisible threads from the tree canopy and swinging in the breeze? You might see only one but there are others nearby dropping from the same tree. These are hickory tussock moth caterpillars (Lophocampa caryae) traveling from their natal leaves.

Here’s what one looks like. Why is it climbing? Read on.

Last month the caterpillars were just a cluster of eggs, laid by their mother on the underside of the leaves they prefer: hickory, walnut, pecan or blue-beech. Their parents found each other by unusual means.

Arctiids have a thorax that comes equipped with a sound-producing organ. The moths “vocalize” to attract mates and to defend against predators, emitting ultrasonic clicks [>20,000 Hz] that advertise their identity. Because an animal that is able to make sound probably needs to be able to hear it too, Arctiids have “ears,” also located on their thorax.

— paraphrased from The Bug Lady’s Hickory Tussock Moth account

The parents die after reproducing but the young live on. When they hatch the caterpillars are toxic so they safely feed in a crowd, eating leaf tissue between leaf veins and skeletonizing leaves.

After they’ve eaten everything in sight they have to move on so they spin out an invisible thread and swing to another branch or tree. The caterpillar in my video had missed the other vegetation and was hanging over a wide gravel road. Perhaps he could see nothing green below so decided to climb the thread back up to the trees.

Read more about their life cycle in Bug Lady’s article Hickory Tussock Moth.

p.s. Did you know that National Moth Week is only 6 days away? 23-31 July 2022.

Help map moth distribution and life history. Attend or start a National Moth Night event (called “mothing”) to contribute scientific data about moths.  Join friends and neighbors to check porch lights from time to time or set up a light and a white sheet to see what’s in your own backyard.

14 July 2022

Though daddy longlegs or harvestmen (Opiliones) resemble spiders they are not even closely related to them. Harvestmen are harmless and have many characteristics that set them apart from spiders including:

• A fused body that appears to be 1 segment. Spiders have a “waist.”
• A single pair of eyes (2) at center-front. Spiders have four pairs of eyes (8).
• Cannot make silk. Spiders make silk and spin webs.
• Cannot regrow a leg that is lost. Spiders can regrow legs.
• No fangs or venom. Spiders have both.
• Eat solid food. Spiders have to liquefy their food, then suck it in.

Harvestmen are members of the class Arachnida that includes spiders, scorpions, ticks and mites. Their closest relatives might be mites, though this is in dispute.

Ironically, harvestmen are sometimes plagued by mites, as shown above and described in this vintage article:

Learn more about harvestmen in this 4-minute video. You may want to watch it more than once. The narrator speaks quickly!

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

8 July 2022

When Mike Fialkovich sent me photos of a regal moth laying eggs on a metal fence near his office I wondered if this female was making a mistake. The fence has no food for her tiny caterpillars. What will her larvae eat when they hatch?

The regal or royal walnut moth (Citheronia regalis) is the largest moth north of Mexico with a wingspan of 3.94 to 6.25 inches (females are largest). The adult moth never eats — its only job is to reproduce — but its caterpillars feast on trees including hickories, pecans, black walnuts, sweet gum, persimmon and sumacs.

Normally their lives unfold like this.

Adults emerge in late evening and mate the following evening. Females begin laying eggs at dusk the next day, depositing them in groups of 1-3 on both sides of host plant leaves. Eggs hatch within 6-10 days, and the caterpillars (known as the Hickory Horned Devil) feed alone. Young caterpillars rest on the tops of leaves and resemble bird droppings, while older caterpillars appear menacing because they are very large and brightly colored with red “horns” near the head. Caterpillars pupate in a burrow in the soil.

— Royal walnut moth account at butterfliesandmoths.org

There’s no explanation for why this moth chose a fence. Did it “smell” like a hickory?

Her caterpillars, called hickory horned devils, will need a lot of food to reach this size before they pupate.

It looks like a mistake to me but we’ll have to wait and see.

(photos of regal moth by Mike Fialkovich, hickory horned devil photo from Wikimedia Commons)

30 June 2022

It’s that time of year again when yellow poplar weevils come out en masse for their courtship flight. I had a hint that they’d “bloomed” when I saw one on my window on 24 June. Today there are more.

This week they were clearly present when I walked through Schenley Park. I brushed off one that landed on my shirt while I watched northern rough-winged swallows wheeling overhead. Were the swallows eating flying weevils or something else?

Yellow poplar weevils (Odontopus calceatus) are harmless to humans but can show up in unexpected places. When I got home I sat down to eat lunch and a weevil jumped off my shoulder and landed near my salad. Dang! I smashed it before I realized I could have taken a closeup photo.

This weevil is not evil but is certainly annoying. Learn more about its lifestyle and what it eats in this 2018 article.

p.s. Years ago these bugs were misidentified in the newspaper as “billbugs.” Every year I forget their “weevil” name until I look them up in June.

(photos by Kate St. John)

7 June 2022

If you want to avoid mosquito bites, there’s new research on how to do it.

Female mosquitos must eat blood in order to produce eggs so they fly around looking for a host. A new study led by the University of Washington teased out an additional way that mosquitos find us.

“I used to say there are three major cues that attract mosquitoes: your breath, your sweat and the temperature of your skin,” said Riffell, who is senior author on the paper.

“In this study, we found a fourth cue: the color red, which can not only be found on your clothes, but is also found in everyone’s skin. The shade of your skin doesn’t matter, we are all giving off a strong red signature. Wearing clothes that avoid those colors, could be another way to prevent a mosquito biting.” …

Without any odor stimulus, mosquitoes largely ignored a dot at the bottom of the chamber, regardless of color. After a spritz of CO2 into the chamber, mosquitos continued to ignore the dot if it were green, blue or purple in color. But if the dot were red, orange, or black, mosquitoes would fly toward it.

— Good News Network: Avoid Mosquito Bites by Ditching These Colors of Clothing This Summer

This wasn’t just a few mosquitoes. The study tracked more than 1.3 million mosquito trajectories and found that they ignore green, blue or purple, and are attracted to red, orange, or black.

Now that we know about colors, who in this group will attract the most mosquitos?

Find out more at Good News Network: Avoid Mosquito Bites by Ditching These Colors of Clothing This Summer, or read the original study at Nature Communications: The olfactory gating of visual preferences to human skin and visible spectra in mosquitoes.

p.s. The study also said: “CO₂ induces a strong attraction to specific spectral bands, including those that humans perceive as cyan, orange, and red.” Cyan looks blue-green to me.

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

10 June 2022

A study of fire ants (Solenopsis invicta) published in April 2022 shows them using nearby materials to build a bridge without any training on how to do it!

Another remarkable example of tool use in ants: fire ants “paving” sticky surfaces. I’ve seen signs of this behavior, but I didn’t expect it to be so robust until my friend told me about it (Wang et al., 2021 Insect Science). pic.twitter.com/BaHBmlgtXM

— Horace Zeng (@horacezhl) March 14, 2022

Ants may not be “smart” but they sure cooperate better than us humans.

(fire ants photo from Wikimedia Commons, embedded video tweeted by Horace Zeng @horacezhl)

14 April 2022

Have you been sneezing this week in Pittsburgh? Are your eyes itchy and watery? Pollen season just began and I can tell you which trees started it.

Pittsburgh is a deciduous place so we’re not contending with pine pollen. Instead we have wind pollinated deciduous trees that bloom before leaf out so their pollen will move freely in the forest.

When our landscape looks like this there’s pollen in the air.

The first to bloom are elms and maples.

American elms (Ulmus americana) are 100% wind pollinated and insure they don’t self-pollinate by producing female flower parts before the male parts mature. By the time the flower dangles in the wind the female parts are hidden.

The dark nobs below are pollen-loaded anthers.

And there are lots of them!

The structure of sugar maple flowers (Acer saccharum) shows they’re designed for wind pollination.

Red maple flowers (Acer rubrum) are more discrete, pollinated by both wind and bees.

Yesterday the temperature was warmer outside than inside so I opened the windows to pull in warm air. This morning my husband’s eyes are itchy. Uh oh. I raised the indoor pollen count. Mistake!

Spring green? Tree flowers! Ahhhh cho!

p.s. This spring is off to a slow start so we started sneezing later than last year. 😉

(photos by Kate St. John except for elm flowers in hand by Rob Routledge, Sault College, Bugwood.org)