Continuing on the theme of strange predators here’s interesting news about a plant that preys on insects.
Nepenthes gracilis is a tropical pitcher plant native to Indonesia, Malaysia and Thailand. Like all pitcher plants it eats insects by trapping them in the digestive fluid at the bottom of its tubed-shaped pitcher. The inner surface is slippery when wet to enhance the trapping effect.
This is dangerous for an insect, so why would an ant bother to get near the pitcher opening? Why would it go under the lid?
Nepenthes gracilis tempts insects with a tasty nectar coating on the underside of the lid. In fair weather a skillful bug can perch on the edge, eat the treat, and walk away.
But in the tropics it rains often and heavily. Sometimes insects seek shelter under the lid or are eating underneath it when the rain begins… and then…
Researchers discovered that heavy raindrops prompt the insects’ demise. The lid is poised like a springboard. The weight of a raindrop springs the trap and catapults the insect into the bottom of the pitcher.
(photo from the PLOS One article by Bauer, U., B. Di Giusto, J. Skepper, T.U. Grafe & W. Federle 2012, (CC-BY-SA), Wikimedia Commons. Click on the photo to see the original)
While at Cape Cod I was fascinated by the wide variety of hermit crabs in the tidal pools. Each crab has a mobile home. The tiniest wear cone-shaped whelk shells. Larger ones wear round snail shells. They’re all in marvelous shapes and sizes.
Hermit crab housing is not a steady state. The ideal shell has room for the crab to grow and allows him to retract in the face of danger. When the shell’s too small the crab is vulnerable.
As he grows, an individual hermit crab is forced to acquire a series of larger shells but a right-sized shell is not always easy to find. His quest is most successful when he joins a house hunting social group.
Though their name is “hermit” these crabs work together when shells are not extremely scarce. Their cooperation was not well understood until researchers from Tufts University and the New England Aquarium teamed up to study the Social context of shell acquisition in Coenobita clypeatus hermit crabs, published in April 2010.
According to researcher Randi Rotjan, “Hermit crabs are really picky about real estate because they’re constantly getting thrown back into the housing market.”
When a hermit crab needs a new home he keeps his eye out for any larger shell. When he finds one that’s empty, but too big, he waits next to it. He won’t use this shell but a larger crab will … and that crab will be in a smaller shell … and that smaller shell might be just the right size. So he waits.
Pretty soon this lone hermit crab has attracted a variety of others who are also in the housing market. They mill about, waiting. The smaller ones piggyback on the larger ones and ride around like papooses. They don’t want to miss their chance.
Eventually all the crabs are lined up by size in a synchronous vacancy chain. The crab who wants the large empty shell is in place and bang! “The chain fires off in seconds, just like a line of dominoes,” says Rotjan. Everyone moves in at once.
Big move-in events are not unique to hermit crabs. This is Move-In week at Carlow, Chatham, Duquesne, Point Park, Carnegie Mellon, and the University of Pittsburgh.
We’re about to see a lot of synchronous vacancy chains in Pittsburgh … but they won’t fire off in seconds. 😉
At Pitt on Thursday, Karen Lang and I were surprised to see both adult peregrines snoozing in nooks high on the Cathedral of Learning. It’s been weeks since both were visible at the same time.
Lately they’ve been in Lawrenceville.
Sharon Leadbitter checks St. Augustine’s cross every day. On Tuesday she saw Dorothy.
August is prime time for observing pokeweed (Phytolacca americana), a tall perennial that’s easy to find in waste places and along roadsides. Though its name is “weed,” I love its colors.
In winter pokeweed dies back to the taproot but by August it’s 6-10 feet tall with spreading branches. The succulent stems are stout and reddish with deep green alternate leaves up to 16″ long. This plant is big.
Pokeweed’s flowers bloom on racemes that curl up while flowering and droop down when heavy with fruit. This month you can see the flowers and fruits in all stages of development, often on the same raceme.
Here the flowers show five white petal-like sepals and nascent green berries in their centers. Notice how the stem is pink. Pink, white, green.
Pokeweed flowers from bud to incipient fruit (photo by Kate St. John)
After the flowers are pollinated the green berries grow larger. On this stem the berries are all the same age, but that’s pretty rare.
Unripe pokeweed fruits (photo by Kate St. John)
More often the berries range from unripe green to ripe blue-black on the same stem. This raceme shows nearly every stage in the berry life cycle.
Mix of unripe and ripe pokeweed fruits (photo by Kate St. John)
Ripe pokeberries are a favorite food for catbirds and cardinals, robins and mockingbirds, thrashers and waxwings. When the berries are gone the empty stem puts on a final show in gorgeous magenta.
Pokeweed stem after the fruit has been eaten (photo by Kate St. John)
Like many plants pokeweed is toxic though if properly prepared the young shoots can be eaten in Spring. The song about eating pokeweed, Poke Salad Annie by Tony Joe White, might lead you to believe lots of people eat it.
NASA satellites have uncovered fascinating things about our world. One of them is shown on the spinning colored globe above.
This 15-second video is a composite map of lightning flashes observed by NASA OTD and LIS instruments from April 1995 through February 2003. Places with virtually no lightning are white, low levels are purple, then increasing amounts pass through the colors of the rainbow finally to red, black and white again.
Let’s slow it down and look more closely. Here’s NASA’s static map of the same thing showing the distribution of lightning per square kilometer per year.
It’s interesting to note the hot and cold spots:
Lightning is far less frequent over water than land.
It virtually never occurs at the poles.
Winter is a great lightning suppressor. I can count on one hand the number of times I’ve seen lightning while it’s snowing. Those times were quite memorable.
The worst place for lightning in the U.S. is Florida.
Be careful in Singapore, northern Columbia, and Kashmir.
There’s so much lightning in equatorial Africa that the map-maker ran out of colors!
Clearly it’s unsafe to play outdoors in the DR Congo. It’s hard to imagine how people cope with it there.
p.s. We had some sneaky lightning yesterday afternoon. A downpour, then the rain stopped and while everything was dripping… BAM! It sounded like an explosion. I’m glad I was indoors.
Agroforests are “a type of farm where the crops are grown under trees at a reasonable density,” according to study author Çagan Sekercioglu. “Often, it’s not like forest-forest — it feels more like a open park.”
In the past, coffee and chocolate crops were both grown in agroforests — or in full tropical forest — because they are shade-loving plants.
But agri-business found even moderately shady habitat too labor intensive. Always on the lookout for ways to cut costs, they bred coffee bushes to tolerate full sun. For the past two decades they have cleared land, planted coffee in the sun, and harvested it mechanically.
Sadly, bird diversity drops as the habitat becomes more open. The study analyzed over 6,000 species and found that the more open the land, the fewer insect-eaters (flycatchers and warblers), fruit eaters (orioles and parrots), and nectar-eaters (hummingbirds). Agroforests can support many of these species but the study showed that open farmland supports only seed and grain eaters — and these birds are often considered pests.
Does open farmland south of the border affect “our” birds?
Yes. Most of our breeding forest birds are neotropical migrants who spend less than half their lives in North America. The majority of their time is spent in tropical forests — or agroforests — in Central and South America.
Every year there are fewer intact forests and fewer agroforests. Meanwhile many of our neotropical migrants are in decline including cerulean warblers and scarlet tanagers.
You can help. Your coffee is good for birds if it’s made in the shade.
How do you know if coffee is shade-grown?
Check the label for bird-friendly, shade-grown certification by a trustworthy environmental organization such as the Smithsonian Migratory Bird Center (SMBC) or the Rainforest Alliance. (Unfortunately some manufacturers have co-opted the term shade-grown because they know it’s worth more.)
Certified bird-friendly coffee and chocolate(!) aren’t always easy to find. If you have a favorite place to buy them, let us know by leaving a comment.
(photo by Fernando Rebêlo from Wikimedia Commons. Click on the caption to see the original)
Click here for more on the University of Utah bird study.
These flowers look beautiful and innocent, visited by butterflies and bees, but there are assassins in their midst.
I should have known there would be predatory insects in this setting but I was surprised to learn about assassin bugs.
There are over 4,000 species of them, all characterized by a short 3-segmented curved beak that lies in a groove between their raptorial front legs. They eat by sucking liquids. The beak is their killing tool. Their victims are insects, caterpillars and bees.
After grabbing his victim with his front legs an assassin bug brings his beak forward, stabs his victim, and injects enzyme-filled saliva that paralyzes the victim and liquifies his insides. The assassin bug then sucks the liquified innards out of his prey.
Ewww.
You can see the deadly beak curled under the head of the assassin bug pictured below. There are graphic photos of these bugs eating insects, but I’ll spare you.
Most assassin bugs are active hunters on trees, bushes and weeds but one group, aptly named ambush bugs, lies in wait on flowers. They’re camouflaged by yellow, orange or red body parts so their victims can’t see them. Then they pounce.
This ambush bug matches the black-eyed susan and wears pollen as a disguise. He even appears to be smiling for the camera. Don’t be fooled.
Fortunately the vast majority of assassin bugs are uninterested in mammals and won’t bite humans unless mishandled.
I shouldn’t be surprised by that either. Never mishandle an assassin.
(photo credits: flowers by Kate St. John.
Assassin bug (UGA1435167) by Clemson University, USDA Cooperative Extension, Bugwood.org
Ambush bug (UGA2106054) by David Cappaert, Michigan State University, Bugwood.org)
Blooming now in Pennsylvania, the evening primrose fully opens at twilight. Similar species called sundrops are open during the day.
Both flowers are in the Oenothera genus and are masters at opening and closing in response to light. It takes these flowers only a minute to do it. Click here to watch one opening.
Evening primroses are hardy and widespread, in fields and along roadsides. Dianne Machesney found this one at Scotia Barrens.
(photo by Dianne Machesney)
p.s. Monday August 13: It’s cloudy and gray this morning. Evening primroses are open in Schenley Park.
