Spiny Spiders of Fall

Spiny Spiders of Fall

Spiny Micranthena (Micrathena gracilis) (Photo: K. McDonald)

What is that Spiny Spider?

There's magic to fall, and the cycles that ramp up (or down) before the cold. You'll start to see all sorts of animals scurrying around caching nuts, humming birds stocking up on nectar, and general mayhem before the birds depart on their way south. To me, there are three signs that fall is coming:

  1. Black gum tree leaves change their color (they're the first to turn red, along with poison ivy)
  2. Fungus starts popping up everywhere
  3. Spider webs smack you in the face constantly on the trail and you have to dodge spiny spiders.

This leads me to helping you identify those pesky spiders that you're dodging on the trails in fall.

WHY ARE SPIDERS SO PREVALENT IN THE FALL?

Let's start with why you might notice spiders more in fall. Well, they've always been there, you've just never noticed or seen them. By nature they are secretive wee beasts and many of them only come out at night or build webs in unnoticeable places. However, they are becoming more active for a variety of reasons, the first and foremost is that many species of spiders breed in Autumn and lay their eggs in leaf litter to over-winter until Spring. The second  is that many young spiderlings that have hatched over the summer are now dispersing for the Autumn so that they too can find a good spot to feed-up before winter. Here's where you flash back to "Charlotte's Web" the children's story book. Baby spiders balloon, or send out long filaments of spider silk from their rumps that act like butt-kites and lift them off and away into the wind. Not gonna lie, I've wanted to do something similar a time or two (though not from the rump, I know your minds went there).

SPINY SPIDERS

FIRST A DISCLAIMER: all the spiders presented here are harmless wee beasties, they don't have a venomous bite, chase women and children, or cause harm. They are beneficial spiders that are quite shy and want to get the heck away from you as fast as possible.

So what are the spiny spiders you're seeing?  In this area (the Eastern US) the most common spider you see in fall is the marbled orb weaver (and orb weavers in general). it's a bright orange spider, about the size of a pencil eraser or dime, but it has a round rump and isn't spiny. if you're curious you can read another article I wrote on this one here.

Marbled orb weaver spider (Photo: K. McDonald)

The two most common types of spiny spiders are the spiny orb weavers in the genus Verrucosa (Ver-rue-cose-ah) and the Micranthena (Mike-ran-thee-Ah) orb weavers. While the genus names of these spiders sounds like a Harry Potter wand curse (I'm sure many people would like to Expecto-spiderum), they really represent two broad groups, the arrowhead-shaped spiny spiders and the club-shaped-spiny-rump spiders. Check out the pictures below to see what I mean.

Micrathenna spider (Photo: K. McDonald)

Verrucoas spider (Photo: K. McDonald)

The Verrucosa spiders get their genus name from the Latin word meaning "rugged" or "warty." The most common one in our area is the Verrucosa arenata (whose species name means "sand" in Latin, from the term "arena). Some entomologist in a dark hole somewhere thought naming these spiders warty sand was a good idea...

Verrucosa arenata (Photo: K. McDonald)

Notice the arrow shaped triangle on its rump. Most orb weaver spiders in this spider's family hang in their webs with their heads down, but this one can be found hanging head-up, and unlike other spiders it rests with its legs tucked up to its body. Not sure why but it's a good diagnostic. The other neat thing is that this spider builds a new web every day, and takes down the old one and eats it at night (recycling at its finest). They're usually about 5-10 mm.

Let's move to the Micrathena. The most common species you see here is the spined Micrathena (Micrathena gracilis), from hence forth called the spiny-rumped spider with a club-butt.

Micrathena gracilis (Photo: K. McDonald)

I have eaten more webs from this spiny spider than anything else. They love to build towering webs across trails and open spaces (often 5-6 ft across), waiting for you to walk into them and do the crazy spider waving arm dance that follows trying to get the web off. Maybe they get a kick out of it..spider humor?

Micrathena gracilis (Photo: K. McDonald)

This spiny spider is unique because only the females use silk to weave webs, and the males look totally different, about 1/2 the size (females are usually about 8-10 mm). The female's abdomen has 8-10 spines and is black and white, with a cone shaped club-butt. The males are not often seen, but they can be found hanging out in the corners of the web, waiting for the right time to mate and dash out without being eaten by the female! There are over 100 species of Micrathena, so don't be surprised if you find other colors, like the one below.

Here is another species of Micrathena, though this one has different colors than the spined Micrathena gracilis (Photo: K. McDonald)

If you live in the Southeastern US you may be familiar with the spiny-backed orb-weaver (Gasteracantha sp.). These little gems are small, round, and spiny too (6-10 mm). They are also in the orb-weaver family.

Spiny-backed orb-weaver (Photo: Wiki Commons, by Marcosenrosen)

There are many more types of spiny spiders but these two groups and spiders are the most common out in Fall. You can always go to Bugguide.net to put in pictures of things you find to get identified.

Check out these additional resources for more information:

You can read the fun article, with great pictures, from Mother Earth News, all about different types of spiny backed spiders here.