Saturday, November 23, 2013

"Two-headed" caterpillar with black and white pinstripes

  Today I walked past a vine where back in early October I saw a caterpillar which looked like it had two heads.  Each end of the caterpillar looked like a black head with white spots.  The caterpillar, which is called a Turbulent Phospila (Phosphila turbulenta), has a whole lot of black and white pinstripes with a bit of yellow  on its sides just above its legs.
  Here is a photo of the caterpillar of a Phosphila turbulenta on a Greenbrier vine.  Notice the upper end (the fake head end) is swollen and has white spots and markings to make it look almost exactly like the caterpillar's real head.
Turbulent Phospila (Phosphila turbulenta) on greenbrier vine
     A head on each end... I wonder if bird's brains can figure out which end is up?  I suspect a fake head could give the caterpillar a fighting chance should a bird choose to peck its hinder end instead of its head.  I wish now that I would have acted bird-brained and "pinched" the wrong end just to see if this caterpillar was chemically defended in some way.  As smartly colored and brightly patterned as the caterpillar is, I suspect it is chemically defended and therefore distasteful to birds.  It follows that they have little need to hide... perhaps that is why I spotted the caterpillars as I was walking trail.
   The photo below shows another Turbulent Phosphila caterpillar that was feeding on a leaf elsewhere on the same Greenbrier vine. 
caterpillar of Turbulent Phosphila feeding on greenbrier
In fact, there were many of these gregarious caterpillars scattered around on the Greenbrier vine.  When the caterpillars were young they would have been feeding on the Greenbrier in close proximity to each other - feeding in groups - probably for safety in numbers.  As they grow they must wander off on their own, at least on their preferred host plant, the Greenbrier.

   I encountered these black-and-white striped caterpillars back in October.  Now, in late November with winter fast approaching, what are these caterpillars doing?  Well, in the leaf-litter on the ground nearby a Greenbrier vine you might find a withered, lumpy, folded-over leaf that feels a bit heavy for a dried leaf...
In the photo below, you can see I pulled the leaf slightly apart to reveal a pupating Turbulent Phosphila.  Within the enclosing leaf the pupa was encircled with a ring of silk and "junk" which formed a "cell" or partial cocoon.
pupa of Turbulent Phosphila
Barring unfavorable environmental conditions, predators, or parasites, that pupa should turn into a rather nondescript, camouflaged, grayish-brown moth come spring.  I think I have a photo of one of these moths that I had taken last spring but can't seem to find it... too plain-looking, eh?

   On the same Greenbrier vine as these caterpillars I also noticed a little pile of trash that was moving... there was a tiny trash collector sidling along the vine.  Can you tell that I, like always, didn't get very far on my nature walk?  Oh well, that little creature will make the subject matter of my next post and so we will continue this nature walk/field trip on a vine with tiny camouflaged trash collectors hiding out nearby where flashy, pinstripe-wearing "two-headed" Turbulent Phosphila caterpillars are feeding contentedly.

Wednesday, November 20, 2013

A Fallen Leaf Story

I reckon a fallen leaf can tell a story.

   When I saw a Catalpa leaf that had fallen in our yard, I was reminded of a phenomenon that happens during the summer.

Can you see what I saw?  Can you picture what happened on this leaf last summer?
dark spots are extrafloral neactaries on catalpa leaf
   See those dark spots along the midrib or main veins of the leaf?  Those spots are the extrafloral nectaries on the catalpa leaf.  During the summer those nectaries attract quite a variety of insects.  I can see them now.... Ladybugs, little iridescent bees, ants, yellow jackets, and so on.  Why does a tree attract these insects to its leaves?  Well, many of them are predators and while they are hanging around enjoying the nectar on the leaf they might encounter some caterpillars or other insects that are feeding on the leaves.  I went into much greater detail in an earlier post about the extrafloral nectaries on catalpa leaves.
   I reckon that fallen leaf, with its outstanding spots, reminds me of how lively a place it was a few weeks ago.

BTY, last fall I wrote a post about another fallen leaf... an aspen leaf with a cute little stem gall.

Saturday, November 2, 2013

A Fall-blooming Orchid

   We were driving down a forsaken stretch of dirt road recently when I spotted some ladies'-tresses orchids that were growing by the side of the road.  I exclaimed to the boys, "Hey, orchids!" as I slammed on the brakes and backed up to have a look.
Ladies'-tresses orchid - Spiranthes sp.
   Yes, there they were.... a couple of ladies'-tresses orchids with their spiraling spikes of small white flowers.  After getting out and exploring the vicinity, we found quite a number of these orchids growing on a wasteland of old stripping piles through which the road had been cut.
   Here is a photo of my camera and tripod set up to take photos of the orchids. 
   There's not much of a road.  Perhaps it's good it was practically an abandoned road, for a few yards down the road, I knelt to take some of the photographs and to take in the faint, pleasant scent of the orchids.  I wish I could describe their sweet scent.

Ladies'-tresses orchid - Spiranthes sp.
   There are many species of ladies'-tresses and they are hard to tell apart.  I think these might be Yellow ladies-tresses (Spiranthes ochroleuca) because of the habitat where they were growing and the time of year they were blooming.
Ladies'-tresses orchid - Spiranthes sp.

A ladies'-tresses orchid pollination system.

   You may know that I am fascinated with the variety of pollination mechanisms that orchids employ to insure cross-pollination.  These particular ladies'-tresses orchids are no exception, so I might as well share with you, my worldwide readers, what I pointed out to the boys (and others).
   First, notice how the flowers spiral up the stem.  The lowest flowers on the spike open first, so the ones further up are 'younger'.  As the flowers 'age', the internal structure of the flower changes and they effectively turn from male flowers into female flowers. That means the younger, male flowers are near the top of the spike.
Now, let's picture how that works to help insure cross-pollination.  Generally, the visiting bees (bumble bees) will work their way up the flower spike... thereby visiting the older (female) flowers first with pollen from another ladies'-tresses.  Then, when the bee visits the higher, younger, male flowers, some pollinia are strategically lurking where they can be glued to the bee's probing proboscis.... to be carried away to another ladies'-tresses growing elsewhere.

I labeled the orchid's pollination system in this photo of a cross-sectioned orchid.
ladies'-tresses orchid pollination
   In a young flower, the viscidium (basically a strip of glue) is positioned close to the 'throat' of the flower where it will easily come in contact, and adhere to, the bee's 'tongue' as the bee sips nectar.  The viscidium is connected to the pollinia, or packages of pollen, as a way to attach the pollinia to a transport mechanism.
   As the flower ages, the viscidium grows farther away from the 'throat' of the flower (more out of the way) and the stigma is better exposed to contact from pollinia from other flowers.
  Simple, yet genius!
ladies'-tresses orchid - Spiranthes sp.
   These ladies'-tresses orchids may have been growing in a forsaken location, but now perhaps, they have been appreciated all over the world.  How cool is that?  I guess that's what happens when a blogger sees an ingeniously designed ladies'-tresses orchid growing by the side of the road.