Sunday, September 4, 2016

September 4, 2016

Sometimes you don't have to go anywhere to witness nature's wonder.  Sometimes it comes and knocks on your door.

This week a brilliant Black and Yellow Garden Spider paid a visit, choosing to set up home on the deck, using Linda's Begonia for a foundation.
Black and Yellow Garden Spider (Argiope aurantia)

This is one of the largest and most recognizable of all the orb weaver spiders and is always stunning to see, especially in this haunt, high up with green trees and the blue lake in the background.
A nice spot for a summer day

She picked a nice spot to spend the summer.  I say "she" because females make these webs - males only occasionally make a web, when they are young and use it for protection.  There are several theories for the purpose of the wide vertical band in the web - called a stabilimentum - including strengthening and stabilizing the web, and providing defense and camouflage.

Perhaps you heard the NHPR "Something Wild" report on yellow jackets recently - they are particularly aggressive this time of year, as their ground nests, fully stocked with larvae, are prime targets of bears and skunks in search of protein.   And they sure can be annoying on a late summer picnic as they land on your potato salad or try to sip your iced tea.  But thanks to this pretty spider, there is one fewer to bother us now.  One afternoon I noticed Mrs. Arachnid was in her usual position, hanging upside down in the center of her web, but there was something else with her, and she had her fangs embedded inside it, sucking out all the juices.
Enjoying a healthy liquid diet

From this angle it was clear it was one of those pesky yellow jackets.
One less yellow jacket to deal with

When she was done with it she carefully unwound it from the tomb she had used to secure it.

She rolled it around, unwrapping and recycling the silk to be used again.

Her dexterity and deftness with her legs in handling her prey was amazing. 
The bee unwrapped
Fully desiccated and unwrapped, she released it from her web.
Most orb weavers consume their entire web every night, recovering their thread for a new web to built for the next day's trapping.

I thought I'd give her a little help with her food supply to ensure good egg production, so I caught a fly that had been buzzing around the house that afternoon and tossed it into her web.  I was amazed at how quickly she acted:  before I even realized what had happened, she had run over and secured that fly by wrapping it up in a new cocoon.  I could see six or more threads coming from her spinnerets that were still attached to the cocoon.  And those multiple spinnerets are used to produce at least seven different types of thread!  Some are formulated for strength, some for their sticky property, others designed for wrapping prey or forming an egg sac, and the spider somehow knows how to make the right mixture to use for each purpose. [Ref:  Encyclopaedia Britannica]
Electron microscope image of a spider's silk spigots.  Photo courtesy of MicroAngela

Another evolutionary wonder!

So next time a spider comes knocking on your door, feel free to show it the exit, but treat it kindly and it will repay the favor by catching its share of mosquitoes, flies, and maybe even a yellow jacket that will no longer be after your burger.

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