Orb weaver - Retribution
Spotted orb weaver with prey
On my blog of August 17, I posted accounts of two spiders. The first was the Spotted orb weaver which I found on my back deck. In that post, I promised to monitor this spider and see if I could capture some predator-prey interaction taking place on the web. More on that to follow later in this blog…..
The second part of the blog was devoted to the spider killing Two-spotted spider wasp. In that post, I had an image of the spider wasp taking care of business with an unsuspecting Fishing spider. Well, it’s time for retribution from the spiders. The prey captured by my back-yard resident orb weaver so happens to be a wasp. By the time I found the spider’s prey in the web, the spider had already encased much of its prey in silk making it impossible for me to detect what species the wasp was. Only a ghostly silhouette made possible the fact that it was a wasp .
One thing that surprised me was that this was in the morning and normally the spider is most active at night like when the posting of August 17 occurred. Apparently, these spiders love to build their webs on back decks and porches as there is ample structure like beams and overhangs to anchor their silk webs, and evening lights from within the house attracts insects. This spider is most likely a female as the males spend their time in the forest in trees and leaf litter while the females are the web builders. A Spotted orb weaver normally lives one year and in the early spring is quite small and reclusive. It is only after they have matured and grown in size that they begin to construct these large webs. The web on my deck is about two feet wide and three feet long. During the night, the spider hangs out at the center of the web like she was in the last posting. During the day, she has certain hiding spots like the small opening created where the vinyl siding of our house meets the molding.
Now, back to the action. This morning, I checked my web and found that a wasp had flown into the sticky silk structure and become ensnared. The spider which has very poor eyesight, sensed the movement within the nest and proceeded to the wasp’s location guided by the vibrations of the web strands. Once she reached the wasp, she immediately began to encase her victim in the sticky thread being extruded by a “spinneret”. The silk thread is originally extruded through this organ located on the underside of her abdomen through spigots as a liquid which quickly solidifies into the thread upon contact with the air. The spider can actually produce different types of silk depending upon the intended use - silk for webs, draglines, egg sacs, and in this case wrapping up its prey.
In the following video I shot of our Orb weaver, watch as she extrudes the silk and then carefully wraps it around the wasp. Normally, the prey is bitten and injected with a toxin as soon as the spider gets to the victim. Apparently in the case of a more dangerous or larger prey, she will quickly immobilize the prey with silk prior to biting and injecting the toxin. Finally in the video, the spider has fully encapsulated the wasp, has immobilized it with her toxins, and quickly takes it to her hiding space. There, the will either store it for future use, or she will ingest the liquid soup produced by the activity of the toxin on the wasp. The orb weaver has no teeth and cannot chew, so the liquefaction is a necessary part of the process. And so, spider-killing Spider wasp, this one is for the Fishing spider!
