Thursday, July 5, 2012

What's with all the grass spiders?

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It's the strangest summer.  Everything has looked like August since the middle of June.  The leaves are starting to yellow and fall, the current weeds are ones you see in August and September, and the yellow jackets are out, even though I usually only see those in September.
One thing that really stands out is all the grass spiders' funnel-shaped webs that seem to have popped up everywhere.  They seem to blanket the hillsides at Radnor Lake, but they are also all over the place in the less-traveled parts of our yard.  They look like sheets of spider web with a funnel in one corner.
Grass spider web.
Since I only remember seeing them in late August and September, I assumed that was their active season.  It turns out that they are active all summer, but the dry dust gets caught in their webs, making them visible.  We are seeing them now because we've only had a quarter inch of rain since the end of May, and everything is really dusty.  Grass spiders are not taking over the world - they've been here all along.

White patches are grass spider webs.
Grass spiders are neat spiders.  They build their sheet web with a little hidey-spout to sit in.  They often dangle some web threads over the sheet too.  Any insect that stumbles onto the sheet or flies into the threads and drops is doomed.  The web isn't sticky, so the insects aren't trapped; rather the web spider is shockingly fast and races out from the funnel as soon as it feels a victim on the sheet.  You can observe this phenomenon yourself if you catch an insect and drop it on a grass spider web. Grass spiders kill their prey with venom, like most spiders do.  They don't bite people, and the venom is harmless to us if they are forced to bite you (if you pick one). 

Grass spider web with funnel in the middle.
Grass spiders are beneficial organisms.  They eat pest insects and help me with pest control in the vegetable garden.  I'm glad to have them in the yard.  They tend to stay put on their webs, so I don't find them in our house very often.  Male grass spiders do go a-wanderin' when it's time to find a mate.  They must have a defined mating season, because it seems one night every spring I walk into my kitchen (near the back door that isn't sealed very tightly), turn on the light, and there are two or three male grass spiders searching for love on the kitchen floor.  Here's a link to see what grass spiders look like (they are only about an inch across, but the picture makes them look gigantic). 

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