Raising Furrowed Orb Weavers

Last July, at a spider presentation in Sarver, PA, an enthusiastic mom/daughter scavenger hunt team found an orb weaving spider with her egg sac. They found a lot of other cool spiders, too – I should’ve asked if they’d be willing to go with me on every spider hunt. Since the spider was displaced and seemed very protective of her egg sac (instead of lay ’em and leave ’em) I took her home and housed her in the largest container I could find so she had room to make a web. At least she and her spiderlings wouldn’t have to worry about being an easy target for predators. A year later, I managed to raise four of the spiderlings to almost adulthood and I’d like to share their story.

Back at the “lab”, I identified mom as Larinioides (pronounced lar-in-nee-OY-deez) cornutus (corn-ew-tis?) AKA the Furrowed Orb Weaver. There are only three species of Larinioides in N. America, north of Mexico. Compared to other common orb weavers around Western PA, they run on the small side only reaching up to 14mm. The cornutus species looks clean and shiny with crisp, lacy markings.

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The Larinioides spiders have a flattened abdomen with dimples.

Mom was in her full-blown prime back in the summer of 2017. She was as large as she was going to get and had fulfilled her mission of making more Larinioides cornutuses. As it goes with most spiders, she died shortly after the spiderlings emerged. Once the spiderlings started spreading out, I kept thirteen and set the rest free among the house bushes. The baby spiders were super small, reddish specks floating on invisible silk strands. They were everywhere! Some flew away on air currents (aka ballooning), some were hanging from my hair, others found their footing on leaves and branches. I housed the spiders I was keeping in 5.5oz. Solo cups and named them LAR 1 through LAR 13.

The LARs all began constructing perfect, little orb webs that were about the size of a quarter (considering the constraints of the container) and started accepting fruit flies. Things were pretty routine for awhile. I would feed them and made sure they had moisture and water. I would get excited when I witnessed one of them catching a fly because most times, a fly would be caught in the web and the spider seemed to be SO SLOW grabbing it as if it were thinking, “Wait..is that a vibration? Oooh! I think it is! I’m gonna go get it…..oh darn.” The fly would eventually struggle out of the web and I wouldn’t know if the spider ever caught the fly or if the fly just died of old age (~a day). As a result of the sporadic fly catching successes, some spiderlings grew faster than others. 6 and 12 were the smallest being half the size of their 4mm siblings. If you don’t have a ruler handy, 4mm is about the size of the Eye of Providence on the back of a $1 bill (if you actually looked, did you notice the spider webs?).

By October, I had seven of the original thirteen losing some to bad molts or some other mysterious consequence. In the middle of January of this year, all of the spiders were  ~6mm and 12 was still a little dink at 4.5mm. I started to notice that they would leave fly carcasses in their webs and orient themselves next to them as if they were using the flies as decoys. Sometimes, a spider would just stay in a tight ball between a twig and the lid and never venture out to the hub. They definitely like hiding. Overall, their schedule was fairly consistent. They would clock into their webs at night (not dusk, full on night) and clock out before the sun wrapped it’s way around to that side of the house (by 7am). In February, I moved most of the spiders into 24oz containers and anxiously checked with a flashlight until I saw the shine of an orb web, meaning they had adapted and were good to go. Fruit flies were still the main course during this time because, although growing, the spiders were still pretty small!

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10 post molt with exuvium at lower right.

In mid March, I thought 10 had died while molting. It’s not uncommon for a spider to have some trouble “shedding” and get trapped inside its old exoskeleton. Under a 20x power dissecting scope, I could see it was not stuck, but actually molting at that very moment! Here is a video of 10 freeing her legs. It shows how complicated the molting process can be!

By April, all of the spiders had graduated from their Solo cups. Not long after the transfer, I was checking the spiders when the lighting revealed a small orb web, about 5″ diameter between the shelves. 12, being the smallest, had managed to get out through one if its air holes and went ahead and set up camp right on top of the other spiders’ containers!

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12’s campsite. The spider was hiding behind the piece of ribbon by the “EEK” sticker.

I thought it was the greatest thing ever! Maybe 12 would grow and thrive and eventually build a giant, beautiful orb web among the house plants! How cool would THAT be?? Well, I got overly excited and tossed a small cricket into the web. The web tore where the cricket fell through it (I knew I was taking a chance with a heavy, “un-flying insect). 12 repaired the web the next day, but a few days later, 12 skipped town. I was hopeful that it didn’t go along the floor because the “Vacuum Evader” spiders would’ve certainly got him or her. Orb weavers are clumsy off their webs and the Vacuum Evaders are experts at snagging floor crawlers.

I got through spring with only 4, 9, and 10 surviving. They are 8mm now and I can see the beautiful details of their markings. It’s cool how they’re all a little different! The spiders are eating moths and larger flies and now reside in 52oz. customized Utz pretzel containers. They could certainly make larger webs if they weren’t confined, but they seem happy and healthy!

This isn’t where the story ends, however. Just a few weeks ago, I was working late at my desk and went to grab a book and guess who I saw?? In the middle of an orb web that spanned the length of a milk crate, was 12! I couldn’t have been happier! I noticed that these spiders don’t tear down and rebuild their webs each night, but do maintenance instead. Their webs are so invisible though, I would’ve never noticed it was there without the spider in the middle of it!

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12!

It’s a lot more challenging feeding 12 flying insects in an open room, but he or she must be happy because it is still there as I write, clocking in every night and hiding in some nook and cranny by 7am. I’d like to keep all the LARs to adulthood to see if they’re males or females and then I’ll let them go. They have work to do out there in nature, making more Larinioides cornutuses and what not. I will surely miss them when they go, especially 12, but maybe he or she will stay if I promise to collect moths in exchange for having the coolest plant room decoration ever!

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