Monday, October 31, 2011

Wild Violet's Explosive Seed Dispersal Mechanism

A violet drama is about to take place.
In the picture below,  a violet seed dispersion event is imminent. 
A violet seed dispersal explosion about to take place
   Violets have an interesting, somewhat dramatic method of seed dispersal by explosion.  This ballistic seed dispersal mechanism begins innocently enough with the seed pods opening to the position in the picture above.  Those pods look like they are just holding a bunch of little BB's. Then suddenly, a random barrage begins with a seed being shot out now and then.  The seed launches are even accompanied by the stalk slightly recoiling.
   A good way to experience the seed launches and the recoil, is to hold some open seed pods by their stems.  You can feel the "kick" when the shots are fired.  Another good way to visually experience a seed dispersal explosion is to prop a few seed pods in a natural position on a table top and place a clear plastic cup over them.  This way when the seeds are fired you can see the stalks recoil and hear the seeds ricocheting around in the cup.
Here are some before and after pictures of the violet seeds dispersal.
The barrage has begun..........                          .........fifteen minutes later.
                
  
   Violet's explosive seed dispersal method is driven by a turgor mechanism (see the collapsing pod just beyond the outer seeds?)...the seed pods dry out and this creates pressure along the sides, squeezing the seeds until one pops out.... much like pinching a watermelon seed or cherry pit until it shoots away.
   In the photo below, a fresh seed launcher is growing up (on the far left) to take the place of a spent launch pad (to the right).
   Another noteworthy seed dispersal strategy of violet species is myrmecochory - seed dispersal by ants.  The seeds have some ant bait attached (elaiosomes) to their exterior. The ants are lured into violet seed distribution as they gather the seeds for their little reward.  After collecting the seeds and consuming the reward, the ants discard the seeds... a neat way of having your seeds transported and planted, eh?   Some other plants that employ this strategy are the Trout Lily and Round-lobed Hepatica.
   Violets flower mostly in the spring and occasionally in the fall.  During the summer and fall, violets have other secret flowers that never open but continue the work of producing seeds.  These self-fertilized flowers are called cleistogamous flowers.  These flowers aren't pretty like the spring ones, rather they look much like the seed pods. Another plant that produces cleistogamous flowers are the Gaywings.
Here is a photo of a pretty violet flower in the spring....
A wild violet flower blooming in the spring forest.
...and here is a photo of violets growing along a wall.
The violets are still producing flowers this fall (the non-opening kind) in order to continue to participate in their seed distribution campaign.
Violets are an easy but captivating example of seed dispersal for kids to observe....
...natural plant seed dispersal with a "kick" and a "trick".

Saturday, October 29, 2011

Dozens Of Chalcid Wasps But No Butterfly

   Chalcid wasps beat me to this Variegated Butterfly chrysalis.  Of course, I didn't know that at the time we found the chrysalis. 
   Recently, some kids came running up to me and said, "Hey, we found a really cool butterfly chrysalis that has gold-colored spikes!"  I'm glad I have extra pairs of eyes watching for cool stuff for me.
Pupa of the Variegated Fritillary Butterfly
The chrysalis was hanging in a piece of plastic playground equipment.  I plucked the chrysalis to hatch out at home... who minds another Variegated Fritillary flitting around?
Well, this is what hatched out today (actually more like two dozen of them) instead of a butterfly.
Tiny wasp approaching a pencil tip
   The tiny wasps that hatched for me today are called chalcidoid wasps.  These tiny parasitic wasps obviously parasitzed the butterfly pupa, leaving it just a pretty, but hollow, shell.  Here is a photo of their exit hole.
Parasitized fritillary chrysalis
   Now, not having a butterfly hatch from the chrysalis was a bit disappointing, but not with dozens of tiny wasps to observe and photograph.
There is a story that goes along with my discovery of the chalcid hatch.
    I was sitting at my desk when I felt a slight sting, or prick, on my arm.  When I looked at the spot, I saw a black speck.  I touched it with my finger and the speck climbed on.  With the realization that the speck was an insect, I reached for my hand lens to examine it closer, but it leaped away like a flea.  So, for awhile I was pondering how I came to be flea-ridden.  Later I noticed, to my surprise and relief, that there were dozens of the same jumping specks on the container with the butterfly chrysalis.
Parasitic wasp
  There are many species of chalcid wasps, so I won't try to id these.  Instead, I'll spend my time with the wasps, taxing my cameras resolution and improving my photography techniques.
Chalcid wasp
Moreover, I can gaze at these tiny wasp pictures and mull over how these parasitoids left me with the empty shell of a butterfly chrysalis.  I am thoroughly intrigued with their life cycle. I could ask many questions. For instance, "How do they locate their prey?"
   Here is a picture of a wasp on a pencil tip to emphasize the minuteness of these chalcids.  The point is, they are tiny, they are everywhere, and they do amazing things.
Oh, I released some of these parasitic wasps.
I believe they went hunting....
 Pupa...chrysalis...egg...caterpillar.......the chalcids are coming!
Which side are you on?  The hunters, or the hunted?

Wednesday, October 26, 2011

The Potter Wasp and its Jug-shaped Mud Nest

A potter wasp fashioned this miniature clay pot.
Mud Nest of the Potter Wasp
 This potter wasp's mud nest is only about the size of a small marble.
 The wasp nest picture below was taken on my skidloader's radiator.
   Besides branches and machinery, I've also seen the potter wasp nests placed in wood piles and in out-of-the-way places on buildings.
   With these fascinating wasp pots showing up here and there, it's  interesting to know about the potter wasp life cycle...
Potter Wasp Nest
 and nice to know wasp that makes these clay pots. 

 The potter wasp pictures below show the jug builders nectaring on small white asters.
Eumenes fraternus - Potter Wasp
 The adult wasps are often seen on flowers. The female wasps are also seen transporting mud balls, making nests, or hunting caterpillars.
A potter wasp - Eumenes fraternus
The potter wasps have at least two generations each summer/fall season.
The potter wasp...
and the wasp pot...a potter wasp's pottery masterpiece.
Wasp Pot.... "thrown" by a potter wasp
   Just think, if I took some mud and shaped this little urn I'm sure the next time it rained my work would disintegrate.  The wasp must have some special ingredient, like her saliva, that helps the mud keep together over the winter.
What happens inside that clay pot?

   After the female wasp shapes the mud nest, she places some paralyzed caterpillars and an egg inside the jug and then seals the opening.  When the egg hatches, the wasp larva consumes the caterpillars. Then it spins a cocoon within the mud cell.  In the photo on the left, I have split open the jug to reveal the wasp larva.  The larva is protruding slightly from its cocoon.
   In the photo on the left, the wasp larva has been removed from its cocoon.  The cocoon is pictured between the larva and the two halves of the jug nest.  This nest was from the fall generation.  The larva will spend the winter in its cocoon awaiting spring when it will pupate ,

   Later, the new adult will emerge as a distinctive looking potter wasp that hunts caterpillars, sustains itself on nectar, and does a good job making pottery.
   There are many types of wasps, but although I'd rather not have any nasty kinds around, the solitary wasps like these potter wasps are totally okay.  In fact, they are genuinely welcome in my back yard.  I mean, who doesn't mind a few little urns sitting around?

Saturday, October 22, 2011

What do earthworms eat?

or, Homeschoolers on The Case of the Missing Face.
   When I saw some leaves disappearing down an earthworm midden, I was inspired to do a hands-on homeschool science project on earthworms for the kids. I called it, "The Case of the Missing Face".  I thought it would be a good way to illustrate the answer to the question, "What do earthworms eat?"
Leaves in a earthworm midden
    I thought this little science experiment would help the kids remember some earthworm facts and I would be able to get some interesting earthworm pictures in the process.
                                                                                                                   We laid a "trap" to catch the culprit who was disappearing the leaves in our yard  by placing a leaf face on the ground one evening.  The next morning most of the leaves had been pulled to surrounding earthworm middens.
They were obviously placed there on purpose and not blown away by a breeze.  Some of the leaves were anchored by fresh earthworm castings.
























   Another night we caught the earthworms "red-handed" as they pulled some leaves of the missing face into their middens.  We also observed other earthworms harvesting various leaves and plant material.
   Earthworms (some people call them nightcrawlers) have vertical burrows which can be many feet deep.  On the surface above their burrows the worms construct little mounds of dirt and plant materials which are called middens. At night the worms stretch part way out of their burrows (hence the nightcrawler name) and feed on plant material. The earthworms pull some of this leaf litter back into their middens. Some of this material they use to disguise their middens , but much of it is pulled below to eat later. This habit of living deep in the soil and feeding on surface leaf litter is termed "anecic".
   Another way we observed what worms eat was by peering down a wormhole.

   In these photos you can see some grass blades and tree leaf parts that the earthworm has pulled down into its burrow.

I lifted off the midden to reveal more of the worm's underground stash.

   The worm's hole is on the left.  There extending to the right, in what used to be the worm's tunnel, is some of the worm's hoard...grass, sections of fresh green leaves, and a whole leaf that had fallen from a tree.  I believe that fallen leaf was once part of the "face".

   I've been known to cross-section insect burrows and even Indian middens, so why not an earthworm midden?  Here is a cross-sectional picture of an earthworm burrow and midden.  The midden mound at the surface has some leaves positioned there by the worm for some reason.  The worm's tunnel extends down the center of the picture and continues to an unknown depth.
Cross-section of an earthworm burrow and midden
  I placed a piece of glass against the cross-sectioned worm tunnel to provide a window into the activities of the tunnel.  I wasn't counting on the rain splattering up the window, but the worm is still visible as it forages partially out of its burrow.  Some leaf litter that has been pulled down into the burrow is also visible in the picture below.

   I took these earthworm pictures at night when they were out feeding.  Taking a picture of a worm at night is a bit difficult.  I had to hold the flashlight, manually focus the camera, and snap the pictures... all without scaring the worms back into their burrows by wiggling the light too much. Therefore these pictures aren't the greatest, but hey, they will suffice to share some information on earthworms.
   In the photo below, the earthworm is stretched out of its burrow and is pulling a leaf.  The leaf slowly gliding across the yard caught my attention in time to get a snapshot.
Picture of a worm pulling on a leaf
   Just before I snapped the earthworm picture below, the worm was stretched over to the upper left side of the picture and was pulling hard on a Common Plantain leaf.  The leaf tore, and the leaf and worm sprang back to their respective corners right as I took the photo.  The plantain leaf that is pointed toward the worm is blurred because of the motion left over from jerking away from the worm.  Notice the worm retains its hold on a fragment of the leaf.

In the picture below, the earthworm was working at dragging the yellow leaf to its burrow.
I guess you could say, "Something is raking my yard for me".
The photo shows why leaf faces disappear, and why soon this leaf won't be blowin' in the wind
Picture of a worm that was dragging a fallen tree leaf
  We've seen some strange things when playing a soft flashlight beam low over the yard...
a blade of grass wiggles...
a  fallen leaf glides a bit, then stands on end...
over there a plantain leaf suddenly jerks upright.
The word for this slow, almost invisible process happening beneath our feet isn't exactly "creepy" nor is it "dramatic".
 This nightcrawler phenomenon is "deep" and "moving", so perhaps the word is..."profound".
   Why not put your own leaf "face" right down there on the ground beside an earthworm midden.  There is a good chance it will disappear.  That's a good way to demonstrate some earthworm facts, like, on a dark night ....things are going down... leaves suddenly tear....and even grass blades disappear.

Monday, October 17, 2011

The Case Of the Missing Face - A Homeschool Science Experiment

We did this homeschool science experiment because some things have been going missing in our yard. 
 I had the boys lay a trap to see if they could determine what was to blame.

One evening we set out a leaf face.

 The next morning the face was missing.
Only one leaf remained where we placed it... the leaf from the right side of the smile.
We observed that most of the leaves had been moved to (incorporated into) little piles of dirt.
  That would seem to rule out a breeze blowing them away.
 Something else must be to blame.
Can you name the culprit who is disappearing our leaves?
Later we caught the culprit red-handed, and I'll post about it next.

Friday, October 14, 2011

Bungee-jumping Caterpillar

I'm sure you've seen a caterpillar that looks as if it is floating in mid-air, but on closer inspection you could see it was actually hanging by a thread.
We recently observed an inchworm hanging on its silk safety line.  Apparently it had dropped from the spruce tree to rappel away from danger.  Some caterpillars use this evasive maneuver to avoid predators.
   When we noticed the caterpillar hanging by its silk thread, it was already reeling itself back up to the branches.  The process of climbing back up the silk line is a most intriguing thing to watch.  The inchworm somehow rolled up the silk into a ball using its legs and jaws.  It manages to hang onto the silk ball with its third pair of legs, roll up the silk, and all the while support its weight on the line.
Here are some side-by-side shots to compare. Notice where the caterpillar is attached to the silk line.
 An instant safety line is a nifty defense mechanism... returning up that line "hand-to-hand" is an amazing feat.

   Since the inchworm was hanging on about four or five feet of line, I had time to fetch the camera and take these photos as we watched it crawl back up to the branches.

 It sure didn't take long, at least not long enough for me to take all the photos I wanted.

Seeing that caterpillar dangling from its line reminded me of a rope swing ride.
The thrill of the launch...the stretch of the rope...the rush of the wind!
I never tried bungee-jumping.  I'll leave that for caterpillars.
Wouldn't it be great though, to have an instant safety line wherever you go?  You could launch yourself out into mid-air until danger passes, and then reel yourself back in.

Wednesday, October 12, 2011

Tiny White Fluffy...

What is this white fluffy flying thing?
A flying fairy?   An eeny-weeny beeny ghost?   A drifting angel?
   No, it's definitely not an angel; it's an aphid. A woolly aphid.
   I saw this tiny white fuzzy bug flying along the edge of a fence row. Even though it looked like a piece of fuzz or lint drifting past, I gave chase because I've seen these white fuzzy insects flying before, and knew how cool they were.  Also, I happened to have my Nikon and zoom lens with me this time, and the thought struck me, " Could I get a picture of an aphid as it was flying?"  Well, yes, but I was always chasing it and didn't get a side shot to show some motion.
   Anyway, then I caught the woolly aphid and let it climb up my finger where I could hold it in the sun for a photo.  Incidentally, I took the close-up picture of the aphid (below) with a Pentax Optio that I had in my pocket for just such an occasion.
This white fuzzy insect is an adult woolly aphid
   Woolly aphids secrete waxy filaments that give them the fluffy look.  The fluff may afford them some protection from predators that would rather avoid mouthfuls of wax.  Woolly aphids suck plant juices.  They can be found on various host plants depending on the species of aphid.
Here is a link for some more information on woolly aphids.
So, if you see a fluffy flying fuzz-ball, perhaps you could chase it down for a close look at its white wispy wax wig.
Here is a link to another Nature Post with pictures of these fluffy flying white bugs.
By the way, an aphid enemy also does the white wax filament thing.  See my post on the
 Ladybird Beetle larvae and its bizarre wax wig.
Oh, and the line,
 "eeny weeny beeny ghost... that rose up in the air" is from a cd of a great storyteller, Bill Harley.