The strange double & triple webs of young Argiope spiders
One of my favorite times of day to be abroad and exploring the natural world is soon after dawn and during that early period when the dew is heavy and it is not yet hot. It seems like a magical time of day when many critters are just waking up. One of the astonishing things you will notice during this time is that there are a LOT of spider webs revealed by the condensation of dew droplets. For an arachnophobe this could be a scary thing, but it just reveals what we all should know, that there are a lot of spiders out there eating insects, which is a good thing in general. Otherwise we would be knee deep in bugs!
What I noticed this morning was that there were a huge number of baby Argiope or garden spiders in our wet meadow grasses. These each had a beautiful web with some interesting differences among them. These orb weavers of course make the familiar circular web with concentric rings and sit in the middle, often on or near a striking zigzag pattern of white silk (called a stabilimenta). Various theories have been advanced as to why a spider would want to make its web more visible either to prey or predators. The leading theory at the moment is that the strip of highly visible silk allows large creatures such as birds to avoid hitting the web, thus destroying the spider’s creation and diminishing its chances of catching a meal and increasing its cost of rebuilding the web. What I was primarily interested in was not this fascinating zigzag creation, but the fact that my baby spiders had either a two or three-layered web design, which I had not previously noticed.
In the attached photo taken from above the web you should be able to see the main orb web with concentric rings of silk in the middle; the spider is hanging on the left side of the web, and there is another loosely organized web on the left and a somewhat less-developed web also on the right side of the orb. Most of the spiders had only two layers, the main orb plus a loose web on the same side as the spider was sitting. Some had another loose web on the other side as well. But what could be the purpose of these extra webs? It seems illogical to have an extra web in essence blocking the prey capture function of the main web, although note that the “outside” web structures are very loosely woven with much bigger holes than the main web. This suggests two possibile purposes for these extra webs- (a) To protect the spider against predators, and/or (b) to protect the main web against damage by insects too large to be captured as prey. Perhaps only the babies make these extra webs? Have any of you observed this phenomenon?
So the next time you have a chance to take a stroll out in a dew-filled morning, go ahead and get your feet wet. You are likely to observe something wonderful that you will miss if you wait until the sun has fully risen. The natural world never ceases to amaze me.
Bill Dunson, Englewood, FL & Galax, VA
wdunson@comcast.net