Cicada damage on an oak tree (photo by Kate St. John)
12 July 2016
After weeks of roaring in late May and June, the 17-year periodical cicadas (Magicicadas, Brood V) are gone but not forgotten.
During the mating frenzy the females used their ovipositors to slit the bark near the ends of twigs and deposit up to 600 eggs per slit. Weeks later the adults are dead but they’ve left their mark on the trees. The slits killed the leafy branch tips.
Everywhere you go in cicada country the trees are green inside and brown at the tips. (This is called “flagging.”)
Cicada damage on an oak tree (photo by Kate St. John)
The trees look as if someone has sprayed defoliant on this year’s new growth. Fortunately that’s not the case!
Cicada damage on an oak tree (photo by Kate St. John)
The trees will be fine. They have plenty of time to recover before Brood V reappears in 2033.
If you lived through the cicada invasion this summer, you won’t soon forget their roar.
If you missed them, your next big chance near Pittsburgh will be Brood VIII in 2019.
Most flowers offer food to attract pollinators. Trumpet vine, for instance, provides nectar for hummingbirds who incidentally pick up pollen and transport it to the next flower.
But some orchids have no food to offer. Instead they look and smell like sexy female insects so the males will attempt to mate with them. In doing so the orchids’ pollen clumps (pollinia) become stuck to the male insects and are taken to the next flower.
Watch the video above from BBCWorldwide to see how it’s done.
Periodical 17-year cicada, Washington Cemetery, Washington, PA, 30 May 2016 (photo by Kate St. John)
3 June 2016
I had to see them for myself.
Thousands and thousands of very loud bugs the size of my thumb with bright red eyes. They’ve spent 17 years of their youth underground to emerge as adults, en masse, for only 4-8 weeks. I didn’t want to miss the spectacle so I drove down to Washington, PA last Monday to see …
17-year cicadas (Magicicada sp.), unique to eastern North America, are so tasty to birds and mammals that they survive by emerging in overwhelming numbers on a prime-number cycle. There are 13 regional Broods with different cycles. This one, Brood V (i.e. Brood 5), lives in parts of West Virginia, Ohio and the bottom left corner of Pennsylvania. Click here for the list of all Broods and regions. Here’s the US map.
In the spring of their 17th year the nymphs dig tunnels that stop just below the surface … and then they wait. The moment of their emergence depends on soil temperature and perhaps on their ability to hear each other making sounds that mean “I’m ready.” (read more here)
They emerge at night and crawl up on trees, plants and walls to shed their exoskeletons and dry their wings. At this point they are very soft and tasty to predators.
Adults and cast-off shells of Periodical 17-year cicadas, Brood V, Washington, PA, 30 May 2016 (photo by Kate St. John)
Periodical 17-year cicada – wings did not unfurl properly. Washington, PA, 30 May 2016. Its . (photo by Kate St. John)
There are so many of them that later arrivals knock the old shells off to the ground.
Periodical 17-year cicada shells, Washington Cemetery, Washington, PA, 30 May 2016 (photo by Kate St. John)
It takes about a week for their bodies to stiffen enough to make their distinctive call. When they’re ready the males congregate in trees and vibrate their tymbals to attract the females. Each bug is individually loud. Thousands of them are overwhelming. Here’s the sound from a cicada-filled tree. The audio sounds like a hiss but it’s actually bugs.
After they mate the females rip a long slit in the bark of a twig and lay up to 600 eggs. Weeks later, the eggs hatch and the nymphs fall to the dirt where they burrow underground to live for 17 years.
Later this summer you’ll know cicadas were here when you see brown leaves on branch tips.
Brown tips on tree branches because of cicada egg-laying (photo from Wikimedia Commons)
No. He could eat them if he wanted to but these barbell fish are his helpers. They eat ticks from his skin and food from his teeth. It’s a symbiotic relationship.
The hippo and the barbell fish are just one example of the unlikely partnerships animals make with other species. Watch the premiere of Nature’s Perfect Partners on Wednesday May 11 to learn about many more — lizards with lions, a fish with a blind shrimp, toads with tarantulas.
Are humans the only species that fools others to survive, find food, and mate? Not at all!
This month PBS NATURE premieres a new three-part series, Natural Born Hustlers, airing on PBS on Wednesdays, January 13, 20 and 27 at 8:00pm (ET) (check local listings).
Episode One, Staying Alive, focuses on survival techniques: camouflage, dominance tricks, audio mimics and playing dead. Early on I was amazed to learn how zebras’ stripes create an optical illusion. You have to see them in motion to believe it!
Other fascinating finds are the amazing skin-morphing camouflage of cuttlefish, the lizard that walks like a stinky beetle, and the white-faced capuchin monkeys who calculate whether they’re needed in battle. “More capuchins are killed by their own kind than by predators,” says the episode. What an unfortunate trait to have in common with humans.
The video excerpt above gives you a good idea of animals’ ingenuity. California ground squirrels use their enemy’s scent as protective camouflage. Their arch enemy is the rattlesnake, so if you hate to look at snakes this video will make you flinch.
And fair warning to those afraid of snakes: Staying Alive has quite a few snakes in it including a match-up in North Carolina of a harmless species that mimics the coral snake. The bonus is that you can identify birds by song on the audio track.
Now that the Greenfield Bridge is gone over the Parkway East, my neighbors are joking that we need a zip line to get to Schenley Park. If we were army ants, we could build a bridge of our bodies to solve the problem.
Native to the tropical rainforest, army ants are famous for their foraging habits. The colony has no permanent home and is always on the move like an army, killing and eating other insects and raiding their nests. The columns of workers are so focused on their task that they overcome obstacles by building living bridges of their bodies across the gaps.
How big a gap will the ants bridge? How do they modify it for different conditions? To learn more about their behavior, Matthew Lutz of Princeton University and Chris Reid of the University of Sydney studied Eciton hamatumin Panama. Their study techniques are shown in the video above.
For instance, they inserted a V-shaped apparatus into army ant paths and varied the angle — 12, 20, 40, and 60 degrees — to see what the ants would do. It turns out that ant bridges are more sophisticated than anyone knew.
Ant bridges are typically 10-20 ant-lengths but the ants don’t start building at the widest spot. Instead, they start from the narrowest point and make the bridge longer to shorten the overall path. They also give up on a bridge if it ties up too many workers to make one. As Iain Couzin, Lutz’s graduate adviser, explains:
“They don’t know how many other ants are in the bridge, or what the overall traffic situation is. They only know about their local connections to others, and the sense of ants moving over their bodies,” Couzin said. “Yet, they have evolved simple rules that allow them to keep reconfiguring until, collectively, they have made a structure of an appropriate size for the prevailing conditions.
Could we humans bridge the Parkway East with our bodies? No. We aren’t long enough and we don’t have enough legs to hold onto each other. Besides, some of us are afraid of heights.
Army ants aren’t afraid of heights. They’re blind (!) and have no idea how far they’d fall if they failed.
Oak gall, Washington County, PA, November 2015 (photo by Kate St. John)
Back in November I found these round hairy growths on the backs of many oak leaves at Hillman State Park in Washington County, PA.
From above they look furry but up close I can see that they’re fibrous.
Close-up of oak gall, Washington County, PA, November 2015 (photo by Kate St. John)
No doubt these are galls, structures grown by the tree itself in response to chemicals deposited by a tiny insect that laid eggs on the underside of the leaf. The insects are usually gall wasps (Cynipidae) whose larvae are protected by the gall.
There are 750 species of Cynipidae in North America, best identified by the characteristics of the gall and the plant it’s growing on. What does the gall look like? What species is it growing on? Where is the plant located (geographically)? What part of the plant is the gall growing on? If on a leaf, is it on the upper or under side? Is it on a twig? A bud? Etc. etc.
Extensive searches of bugguide.net produced similar photos but no final identification. The closest was this one: A gall wasp (Cynipidae) in the genus Acraspis, photographed in Guelph, Ontario.
So I’m back where I started. I know the name of the wasp (as far as I care to know) but what is the name of the gall?
Until quite recently I thought earthworms were native. All my life I’ve watched robins yank them out of the soil and seen them on the sidewalk after heavy rain. Gardeners and composters are happy with them, too, but…
What’s good for the garden is lousy for North America’s forests. Earthworms churn the soil column and devour leaf litter, invertebrates and fungi that our northern forests rely on. The result is a lack of ground cover and poor regeneration of the trees.
Like the emerald ash borer, we humans have accidentally introduced a species that’s bad for the forest. The only way to stop it is for us to stop moving worms and soil. Composters and gardeners take note! If you’re on the edge of the earthworm advance — in Minnesota or Maine, for instance — don’t buy worms. (Pittsburgh isn’t on that edge; earthworms have been here a very long time.)
(robin photo by William Majoros via Wikimedia Commons. Earthworm photo by James Lindsey at Ecology of Commanster, Belgium via Wikimedia Commons. Click on the images to see the originals)
Hemlock wooly adelgid (photo courtesy Sarah Johnson, The Nature Conservancy)
Last week Sarah Johnson at The Nature Conservancy reminded me that early November to late March is the time of year to be on the lookout for hemlock wooly adelgid.
The Nature Conservancy, Pennsylvania DCNR, and the US Forest Service are tracking the advance of hemlock wooly adelgid (HWA) in hemlock conservation areas and the High Allegheny Plateau of northwestern PA and western NY. They need your help.
Hemlock wooly adelgid (Adelges tsugae), originally from Japan, kills eastern hemlocks in 4-20 years by sucking the lifeblood out of them. A hemlock with an adelgid infestation like the one above is doomed.
By knowing where HWA has newly arrived, the survey may be able to treat key trees until a winter-hardy biological agent is ready.
So if you’re out birding in Pennsylvania’s north woods(*) and you see these white wooly balls at the base of needles on the undersides of hemlock branches, it’s the dreaded adelgids. Note your location and contact one of the folks on this list. Do NOT take a sample.
If you’d like to participate in the official survey, call or send email to Sarah Johnson at sejohnson@tnc.org, 717-232-6001 Ext 231.
(photo of hemlock wooly adelgid courtesy Sarah Johnson, The Nature Conservancy)
(*) The survey location runs from Cook Forest to New York’s Allegany State Park.
Evidence of Leaf Miners (photo by Kate St. John) — Other plants mimic this by becoming variegated
13 October 2015
Have you seen plain non-variegated leaves with unusual patterns like these? Did you know the patterns are caused by an insect?
Leaf miners are the larvae of moths, sawflies or flies (and a few others) that eat leaf tissue within the leaf.
The process begins when an adult insect lays her eggs on the leaf. When the larvae hatch they eat a tunnel between the top and bottom surfaces and the leaf turns white where it’s been mined. The mining squiggles are so unique that entomologists can identify the insect species by the pattern it makes.
In 2009 botanists discovered a healthy plant in the Ecuadoran rain forest whose leaves appeared to have leaf miner damage but did not. They wondered if the pattern was a signal so they painted similar white trails on green leaves and compared leaf miner damage on three kinds of leaves: green, naturally variegated, and fake-variegated.
