Green Lacewing: Teenage Hellion

The common green lacewing, Chrysoperla sp., is a welcome insect in my garden and on the farm, but it sometimes reminds me of Dr. Jeckyll and Mr. Hyde.  It has rather alarming personality shifts.   It starts and ends life with delicate, gentle beauty, but it has a dramatic personality change during its ferocious adolescent stage.  

Green Lacewing Eggs

The miniscule space needles growing out of the shefflera stem above are not fungi.  They are the slim, stalked eggs of the green lacewing.  Lacewing eggs are usually laid on the undersides of leaves and stems.  They are a lovely surprise to find when working in the garden.  They seem so fragile that they would break or bend in the breeze, but you can brush your finger against them and they stand back up.  They are so delicate, that I can't feel them, even with my less calloused ring fingers.  They stand in peaceful beauty, glistening in the sun, while their infant lacewings develop inside each egg.  

Watch out, because after a few days, each egg cracks, and out charges a fierce, anxious monster of a teenage insect: the green lacewing larva.  It moves quickly and ranges widely, and it is hungry for fresh meat. It stalks, catches and eats every insect it can catch with its pointy mouth parts.  It kills its prey with toxic venom.  If it were 100 times larger, you would have to fortify your house and never go outside!  I'm certain some dangerous movie aliens are based on these ravenous killers. 

Scary green lacewing larva, source in picture.

After a few weeks, the green lacewing larva begins to feel full.  Its hunger for protein is sated.  It's ready to settle down, take up a peaceful existence and devote itself to future generations.  It finds a sheltered space under a leaf, wraps itself into a silk-bound ball, and metamorphoses into an adult.  The adult emerges, green and shimmering, and spreads its delicate, reticulated wings.  It floats off into the night, sipping nectar, mating and laying eggs.

Green lacewing adult with outstretched right forewing.

Don't fear the lacewing, even in its carnivorous stage.  It won't bite or sting you.  It will, however, remove hundreds of pest insects from your garden.  One lacewing larva can eat 200 aphids in a week!  Some organic gardeners buy and release lacewings onto their farms to help control insects.  Pesticides kill these useful farm workers, allowing pest insects to move back into the area with no predators.  Since pests can usually reproduce faster than prey, if both pests and prey are killed, you're likely to have a worse pest problem in a few weeks when the population recovers.  Encouraging beneficial insects like the green lacewing helps cut down on expenses, work and pesticide usage.  To encourage lacewings, plant flowers that the adults like, for example coreopsis, dill, Queen Anne's lace, cosmos and other similar plans.  You can also leave some of your dandelion weeds, because lacewings love them.

I apologize to my biologist readers for all the anthropomorphizing above, but these little critters seem very dramatic to me. 

Little Green Farm Workers

With the greens of the farm plants fading, two bright green animals brought themselves to our attention on the farm this week.  Both of them are welcome creatures that help us keep the numbers of pest insects low. 

The first green creature of the week, a rough green snake, was hanging out in the barn.  I found him in a basket I was about to use for eggplants.  We quickly caught him and put him in this jar (with air holes), so that the farm owner's son could see him too.  These little green snakes are a rare sight on the farm, and they hold a special place in the hearts of this farm family.  We marveled and the bright emerald luminescent color of this sleek, friendly snake.

Rough Green Snake with grass- we released him quickly!

Rough green snakes don't get large.  They can grow to almost 3 feet long, but they always stay skinny.  They are great climbers and spend their time hunting insects and spiders in any kind of vegetation from grass to trees, but they prefer to be higher up rather than on the ground.  Green snakes are well camouflaged for their preferred habitat, and I've probably seen dozens of them without realizing it.  They coil up in branches to sleep at night, and in the cooler weather, they seek refuge under logs or other debris.  This may be why our green snake ventured into the barn.  He probably thought he found a good place to overwinter.

Later in the week, we were working in the greenhouse, and we found two gigantic praying mantises, both the brightest of green.  One of the mantises was half brown and the other was all green.  I wrote a little about mantids earlier, but here's some more information about them.

In Tennessee, our most noticeable mantids come in three color variations: green, brown, and green plus brown.  The green ones are European mantids, the brown are Carolina mantids, and the green plus brown are Chinese mantids.  Only the Carolina ones are native, and the other two were introduced to the US to help control garden pests.  These introduced species do not appear to be particularly invasive, though they can reduce numbers of helpful organisms like wolf spiders.  People generally regard them as welcome workers in farms and gardens.   There are several other mantis species that are illegal to import because they pose a threat to native ecosystems.  They can probably reproduce very quickly and overeat beneficial insects.

European mantis, about 6" long.

Female mantises are disconcertingly large this time of year.  They grow big from hunting all season, and their abdomens are filled with eggs.  Now they are laying their egg cases on vegetation.  The egg cases look like brown trilobytes - they are oblong with ridges and about 1-2" long.  They are eggs encased in a foamy mass that hardens after it is laid.  The eggs overwinter to hatch in the spring, releasing hundreds of tiny, springy green mantises into the area.  The tiny, thin mantises need to disperse fast, because their siblings pose a significant predation threat.

Surprises of Fall

Fall came so quickly this year.  Today is the first day of fall, but we have had fall weather for the past several weeks.  Spending entire days every week interacting with the earth and plants has made me notice the season's changes much more acutely this year.  Here are the things I've noticed most as the weather has changed:

• The bees and wasps are already gone.  The flowers are still going strong, but that cloud of buzzing has disappeared.  There are still a few slow bumblebees here and there. 
• The spiders are out in force.  Many blooms have their own resident flower spider, and there are lots of webs strung up between the plants.  We had the biggest garden spider I've ever seen in the hoop house. 
  

  

  Garden Spider Source
  

• It feels strange to eat cherry tomatoes when it's cool and cloudy.  The tomatoes taste the same, it's just not as heavenly to pop them in my mouth when I walk by the tomatoes.  Now I want to nibble the turnip leaves.
• The smell of tomatoes rotting in the field is almost intoxicating.  It's difficult to describe why this is so wonderful, but there's a toasty, dusty, cheesy, roasted tomato smell all around the tomato rows from the unusable tomatoes that makes my head spin.  Rotting squash smell great in the field too.  Don't try this at home - it doesn't work without sunshine and dirt.
• The crops are all different now.  Instead of tomatoes, squash and melons, we have turnips (the best vegetable), chard and beets.  It happened so fast.
• The weeds have slowed down a lot, thank goodness.  Even though I can see the scattered crab grass seeds everywhere, and I know what's ahead for next summer, the pressure's backed off a bit for now.
• It's easy to get a LOT done now that it's not 100 degrees.  In the extreme heat, work slows down due to the body's physiological constraints.  These crisp, cool days mean that I can work fast and easily, and everything feels good.
• I only go fill my water bottle once or twice a day now, instead of four or five times.
• Ironically, the work is starting to taper off even as our capacity to do it increases.  Since fewer crops grow during the winter, a lot of the fields are lying fallow, and we have planted cover crops.  Here is the melon field, all disked in and planted with a mixture of vetch, radish and rye for the winter:

  

  This field is done for the year.
  

• The farm is looking more neat and tidy.  With things growing more slowly, there is time to organize and clean up.  June and July felt like a race to keep up with the creeping jungle of crops and weeds, and now it feels like we are getting ahead.

I only have one or two more days to work on the farm, then I'm moving to the heart of Chicago for a while.  I expect the contrast to be a little jarring.  I'll be reporting on what biological phenomena I observe in the city.  In the mean time, I'm savoring the last few hours of fresh air, big skies and working on the earth here in Middle Tennessee. 

Dangerous Animals Week, Part II

Black Widow Spider (Source)

I bet that image caught your eye!  There is no mistaking a female black widow spider.  When you see one, it is startling.  They are so black and shiny, they stand out against any background.  In my opinion, the extreme blackness of black widows is their most charismatic characteristic - even more so than their red markings.  They are the same black as Wonder Woman's hair.  Their red markings are more variable than you learned in third grade.  Yes, they commonly have a red hourglass under their abdomens, but by the time you notice the red abdomen, you've gotten really close and you've turned over the spider, and it's too late!  Several species of black widow have red splotches on the dorsal side of their abdomens, but the southern black widow has no dorsal splotches.  If you see a jet black shiny and fairly large spider, don't pick it up!

I saw two black widow spiders this week on the farm.  That makes five so far this summer.  I've come to expect them in the drier areas of the farm, like inside the hoop house and the barn.  They also seem more likely to be present on human-made structures, like the irrigation equipment, though this week's spiders were low to the ground on plant stems.  Can you see the black widow in the picture below?

Yes, there is a black widow here.

Here I have zoomed in on the unlucky black widow:

There it is!

When you encounter a black widow, you will notice a rather strange spider web.  Black widows weave chaotic, disorganized and somewhat sparse webs.  Their silk seems to be stronger than other spiders if you happen to put a finger through a web.  The silk has been tested, and it's not stronger, but it is very sticky and somewhat thicker than what other spiders extrude.

For a person who, as a child, thought black widows were always on the hunt for an unsuspecting human to bite, real-life black widows seem shockingly meek.  They cower if their webs are disturbed.  They don't jump or run, but they hold still and hope their warning coloration convinces you to just go away.  The spider above seemed to crouch with it's little legs over its head and quiver when I uncovered it.  I was sorry to kill it, but their bites are so dangerous, we can't tolerate them on the farm.

When you look up black widow spider bites, the medical sites reassure you that 'black widow spider bites are rarely lethal'.  Thanks - that makes me feel a lot better!  Actually, I, personally, am not at great risk, but a bite to a child, elderly person or ill person can be fatal.  Black widows produce a very potent neurotoxin that can spread through the body.  It can produce systemic symptoms like fever, sharp pains, nausea, tremors and worse.  The actual bite location itself will be relatively unimpressive, with a small, red, swollen area.

Most black widow bites are not treated with antivenom (aka antivenin, if you're using the French-derived version of the word).  The antivenom is problematic because it is rarely stocked at hospitals, and it's made from horse serum, which can cause major allergic reactions.  If you are bitten by a black widow, treated with antivenom, then bitten by a rattlesnake, you will be in big trouble.  Rattlesnake antivenom is also made with horse serum, and after your first exposure, your immune system will react much more strongly to the second exposure of horse serum.  Use of antivenom can save the life of an at-risk individual, and it can shorten the flu-like symptoms of a healthy person. 

Black widow spiders get their names from one of the behaviors observed in the female black widows.  Sometimes after mating, female black widow spiders eat the male black widow.  Male black widows generally get the short end of the stick in life.  They are very small, their coloration is drab and they don't have enough venom in their bites to bother anyone.  Their main job in life is to mate and pass on their genes, and after that, they may as well provide a little food to the mother of their children.

Now that the days and nights are getting cooler, I've noticed that the cold-blooded animals on the farm have slowed way down.  The chiggers and ticks seem less intent on making life annoying.  The bees and wasps have mostly disappeared.  The black widows have finished laying eggs and have hopefully lost the strength to push their fangs in through the calloused skin on my hands.

Dangerous Animals Week, Part I

Even farmers go on vacation.  Especially when they get married and go on a honeymoon!  We went to Florida over the weekend, and I took the chance to get to know our gelatinous friends of the sea, the jellyfish and comb jellies!  There are many great mysteries in the ocean, and these critters are some of the least understood - even by Biologists.  I suppose even I have been avoiding them all these years.  I have been so blind.

Jellyfish, corals and sea anemones are all members of Phylum Cnidaria (silent C), which means they are radially symmetrical and have venomous stinging structures.  Comb jellies are members of Phylum Ctenophora (also silent C), which means they are also radially symmetrical but have comb-like cilia and are carnivorous.

I pretty much assumed that everything gelatinous and floaty in the ocean would leave painful welts that would become infected and lead to a costly doctor's appointment.  Wrong!  Many jellyfish have such weak stings that humans can't be punctured.  In fact, the ones I most often see in Florida are mostly harmless to all humans except the most thin-skinned.  The cannonball jellyfish, can apparently cause heart problems if you rub your eyes on its short tentacles, but you can pick it up or brush into it with no problem.  The moon jellyfish, according to the guide to Florida jellyfish that I read while on our honeymoon, do not sting humans.  I did not test this myself, but I did manage to convince my husband to pick one up, and it did not sting him.  Subsequent reading about this species reveals considerable difference of opinion about the the moon jellyfish's ability to sting humans, but the most reliable-sounding Internet sources say it can only mildly sting thin skin.  I chalk the reports of dire consequences up to general fear and misinformation about jellyfish. 

Cannonball Jellyfish

Cannonball Jellyfish

Comb jellies most definitely cannot sting.  Reports are unanimous about this, and I tried it out myself.  Below is a brown comb jelly in the water, and below that are two brown comb jellies in my hand.  Comb jellies are shaped rather like a stocking cap with rows of cilia along the long axis.  Those cilia reflect the sunlight beautifully.  Comb jellies can open and close one end of themselves, depending on whether they are eating something or not.  Since comb jellies are transparent, you can see what they have eaten.  Brown comb jellies eat American comb jellies, which are smaller and colorless.  I watched a brown jelly, which had obviously already eaten once already that day, engulf an American jelly in 5 seconds flat.  Once the prey was inside, the brown jelly sealed itself and probably spent the rest of the day digesting and absorbing its two meals.

A swimming (or is that hunting) brown comb jelly.

A brown comb jelly temporarily collapsed into a pile of goo in my hand.

Brown comb jelly in better light with tree reflection.

Of course, many jellyfish can sting in a major way.  The box jellyfish hurt badly, and some found in Australia are deadly.  The man-of-war can put you in the hospital (incidentally, there is a jellyfish called the by-the-wind jellyfish that looks much like a man-of-war but can't sting people).  There are sea wasps, sea nettles, lion's mane jellyfish and more.  I don't recommend learning which are dangerous by trial-and-error.  Here's a good .pdf guide to Florida jellyfish.

My other major misconception about jellyfish and comb jellies is that they can only stupidly float wherever the current takes them.  Again wrong!  While they are certainly not strong swimmers, jellyfish and comb jellies can move toward and away from things like light, movement, smells and salinity differences.  It's true they don't have brains, but they do have nervous systems to sense the environment and coordinate movements.  Some jellyfish even have fairly complicated camera-type eyes!  Many jellyfish only have to concentrate on staying upright.  Others, like the cannonball jellyfish above, can swim quickly up and down in the water to find food.

Bug Beds

Imagine you are an insect, and the nights are getting colder.  You don't really have a home to go to, but you need a place to snuggle in to survive the cooler nights.  There are a million places you could go.  You could hang under a leaf or sit on a tomato flower, but the real Ritz-Carlton of the insect world is the celosia flower, seen here.

Celosia

Celosias are gigantic, fuzzy, and filled with little crevices to lodge for the night.   There is even breakfast in bed for their guests, because the flowers provide plentiful nectar for bees, wasps and other insects.  I imagine it must be very pleasurable to settle in to these soft, velvety flowers.

Hive-less, or solitary bees will often nestle into or under a flower to get through the night.  If you go into your garden very early in the morning, you will undoubtedly find some sleepy bumble bees or wasps curled up inside your squash flowers or daisies.  If the morning is cool, you can even touch the bees - they will be too cold to panic. 

This week, we had an exceptionally cool day.  It was 95 degrees one day and 60 the next.  The bees and wasps (and the rest of us) were caught off guard, and they didn't leave their flowers for the entire day.  As I harvested celosias, I noticed bumble bees, cicada killer wasps, ichneumon wasps and many other wasps and bees sitting inactive amongst the celosia blooms.  I could get as close to them as I wished without disturbing them.  Unfortunately it was also raining, so I didn't get pictures.  You'll have to make do with this picture of a cart loaded with gorgeous celosias that I harvested. 

Cart of celosias

I C4...there I am!

Sorry for the bad pun!

It's the hottest and sunniest time of the year.  That means the C4 plants are about to lap the C3 plants in the race on the farm.  C4 plants are ones that have evolved an extra step to their photosynthesis process that makes them more efficient than other plants, especially during the heat of summer.  Most plants are C3 plants, but crabgrass, sugar cane, corn, sorghum and many other plants are C4 plants.  C4 plants comprise only about 3% of flowering plants, but they do 25% of the photosynthesis that occurs on land*.  Unfortunately, the only C4 plants on the farm are weeds, and the worst of the worst is crabgrass!!!!!

My nemesis.  Notice the star shape of the first few crabgrass stems.

Now brace yourself.  We're going to have to wade into some technicalities of photosynthesis.  Trust me...it's way cool, as the young kids say.  It is imperative that you understand the tricks that C4 plants can do, because if you ever have to spend an entire day weeding crabgrass, you'll want something to think about.

First though, C3.  Think back to 9th grade.  Remember photosynthesis?  It's that thing that plants do to make their food.  The idea is that plants capture the energy that the sun is giving off, and then they use that energy to knit carbons, hydrogens and oxygens together to make sugar.  As we all know, sugar is a basic food.  In plants, it stores the sun's energy in chemical form until the plant needs it.  Sugar is also the basic molecular building block for a lot of the structural molecules plants use to build themselves.  In fact, all the food on our entire planet originated from photosynthesis (even meat because cows get their energy from grass).  Also, all the oxygen in the air on Earth was made as a byproduct of photosynthesis.  So it's kind of important.

Now to the name C3.  The C refers to carbon, which is the most important atom involved in photosynthesis.  Plants collect carbons form the air in the form of carbon dioxide, which they use to make sugar.  The 3 refers to the size of the molecule that the plant uses to 'trap' the carbon dioxide.  In C3 plants, when a carbon dioxide molecule (which has one carbon atom) is caught by the plant, it joins with the plant's carbons to make a three-carbon molecule (called 3-phosphoglyceric acid, or PGA).  Eventually, when a plant has collected six carbon dioxide molecules, it has enough carbons to make one sugar molecule.  In a single teaspoon of plant sugar, there are approximately 1.7 x 10^22 molecules of sugar, so plants do a LOT of photosynthesis.

But, you can't understand the C4s' advantage until you understand the last piece of this photosynthesis puzzle: RUBISCO.  I'm not just typing in all caps because I'm excited about RUBISCO; it's also an acronym.  RUBISCO stands for ribulose 1,5 bisphosphate carboxylase oxygenase, which is a handy phrase to work into almost any conversation.  RUBISCO is the molecular machine, or enzyme, that allows the plant to 'grab' CO2 out of the air and bond it to make the three carbon molecule.  The carboxylase part of the name refers to its ability to bond carbon.  Unfortunately for plants, RUBISCO can also bond oxygen (that's the oxygenase part of its name).  It's unusual for enzymes to be able to bond two different substrates - usually they have one job only.  For RUBISCO, it's a problem to be able to bond two things, because every time the RUBISCO bonds to oxygen instead of carbon dioxide, it costs the plant energy instead of gaining energy like photosynthesis is supposed to do.  In the summer, when plants are photosynthesizing fastest (and producing oxygen, remember), there is even more oxygen around the plant.  So plants are not able to photosynthesize to their full potential because their RUBISCO is wasting more time with oxygen.  Scientists think the RUBISCO problem exists because RUBISCO evolved in plants' ancestors before there was any oxygen in the air to worry about.

It all used to look like the right side before I pulled out the crabgrass.

C4 plants have evolved more recently, and they have solved the RUBISCO paradox.  As you can see in the pictures above and below, the C4 crabgrass is kicking the butts of the C3 beets growing in identical conditions. 

Unweeded beets on the left, free beets on the right.

 Crabgrass, like all other C4 plants, bonds carbon dioxide to make a....drum roll please.....FOUR carbon molecule!!!  Crabgrass has a stand-in molecule that doesn't use RUBISCO to trap carbon dioxide from the air.  This C4 molecule exists near the surfaces of the plants that are exposed to air, where carbon dioxide (and oxygen) is.  It can ONLY trap carbon dioxide and not oxygen.  Once it traps a carbon dioxide, the four-carbon molecule, called oxaloacetic acid, travels deep into the plant away from air.  All the plant's RUBISCO is stored near the center of the plant's leaves and stems, and the oxaloacetic acid drops off the trapped carbon to RUBISCO, where it goes through the rest of photosynthesis like normal.  So you have all of the photosynthesis with none of the waste from exposure to oxygen.  And thus the crabgrass flourishes in the middle of summer when photosynthesis is happening at its fastest.

* Most of the photosynthesis that occurs on earth is done by algae in the ocean.