Peruvian Amazon: Tangled Webs Part VI

Images of undisturbed subjects in their natural environment. All subject types.

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pbertner
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Peruvian Amazon: Tangled Webs Part VI

Post by pbertner »

A tiny spider sits in the middle of a fine net, lightly dusted with a fine mist:

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A ray or slingshot spider (Theridiosoma) pulls back on an anchor thread, creating a tension which is released when a flying insect passes by, snapping the web and entangling its prey:

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A ladder web from a Scoloderus sp., is a specialized tool used for hunting moths. Moths, whose loose scales readily detach are often able to disentangle themselves from spider webs. However, a moth which runs into a Scoloderus web and tumbles downwards gradually loses its scales as it tumbles the length of the web, finally arriving at the round hub at the base, scaleless and defenceless:

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A sheet web spider relies less on the stickiness of its web to catch its prey, and more on its agility and speed to subdue the prey which falls into the web which acts as a kind of pitfall trap, with tripwire/entangling threads above, and bowl-like web below:

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Spiders, especially juveniles or smaller species will travel from one location to another through a behaviour known as ballooning. They release a non-sticky thread from their spinnerets which catches the wind, and carries them to destinations known only to a fickle wind. When there is little air current, or the conditions are otherwise unfavourable, then the thread is reeled back in and consumed so as not to waste energy, like with this juvenile crab spider:

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During the night this cryptic Pozonia sp. sits in the middle of its web like most other araneids. But during the day, it dismantles its web, and relies on its camouflage, which appears as a broken branch, to safeguard against predation.

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A rare, cryptic species of araneid (Macpos monstrosus) doesn't build a web, but releases male moth pheromones to attract its prey, and then awaits with outstretched legs, ready to catch its quarry:

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Spiders produce a variety of silks from their spinnerets, which is actually stored as a liquid crystalline solution, but rapidly polymerizes as it passes through the narrow canal of the spinnerets which strips it of water, coagulating it into a solid. Araneids have up to 7 different types of silk serving different purposes. The non-sticky swathing silk, seen here being produced by a female spiny orbweaver (Micrathena Schreibersi) is used to protect its eggs:

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Harvestmen, like this Cosmetidae don't build webs but lead an omnivorous diet, oftentimes scavenging, other times predating weak or defenceless insects or snails. Many neotropical harvestmen often possess ornate patterning, which additionally fluoresces under UV light:

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Thanks for looking and commenting,
Happy New Year,
Paul

leonardturner
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Post by leonardturner »

As always, I am in awe of your images and impressive lighting abilities, and I always learn something from you descriptions.
I've never seen that pattern on a harvestman before. What UV light source did you use?

Leonard

ChrisR
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Post by ChrisR »

Intriguing visions.

I am reminded of Bergman's title "Through a glass darkly".
Chris R

mawyatt
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Post by mawyatt »

Wonderful images and descriptions.

Really enjoy all your images and enlightening comments.

Best and Happy New Year,
Research is like a treasure hunt, you don't know where to look or what you'll find!
~Mike

Sharnbrook
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Post by Sharnbrook »

What an amazing story! Thanks very much for the enlightenment.
Regards,

Mike

Beatsy
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Post by Beatsy »

Lovely set - as always. The "engineering" of webs has always fascinated me. I read somewhere that spiders use 12 simple rules in spinning webs, but I didn't get any detail on the rules themselves (it was a long time ago, but I think I remember the main paper being blocked behind a paywall).

Lou Jost
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Post by Lou Jost »

Wonderful work again. I did not know about the slingshot spider.

My favorite Tambopata spider is the little one that makes a model, in the middle of its web, of a big nasty spider, constructed from bits of debris. The little spider sits in the center of the big fake spider.

pbertner
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Post by pbertner »

Thanks everyone for the comments and kind words, always appreciated.

leonardturner - The UV source was a Tank007 3W 365nm UV torch. The harvestman isn't rare, but not particularly common either. The cosmetids seem to be more nocturnal as well.

Beatsy - I'll look into it, thanks for the lead.

Lou - Yes, the Cyclosa sp. is a pretty interesting one as well. I've seen them around but haven't seen a particularly well crafted web in a good position.

MarkSturtevant
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Post by MarkSturtevant »

Wonderful job! I especially like the Scoloderus web.
Mark Sturtevant
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santiago
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Post by santiago »

Amazing images, I find the ladder web and "broken branch" fascinating!
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Beatsy
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Post by Beatsy »

Ref: web building rules. While this isn't the paper I was originally talking about, it does contain some interesting info relevant to the topic.

http://www.cs.bham.ac.uk/~jer/spider.pdf

Scarodactyl
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Post by Scarodactyl »

Also of potential interest is that recent studies suggest ballooning spiders rely on electrical phenomena rather than wind.
These threads continue to amaze me. I'd never heard of the slingshot or ladder webs.

santiago
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Post by santiago »

Beatsy wrote:Ref: web building rules. While this isn't the paper I was originally talking about, it does contain some interesting info relevant to the topic.

http://www.cs.bham.ac.uk/~jer/spider.pdf
Nice paper, thanks for sharing :)
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santiago
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Post by santiago »

Lou Jost wrote:My favorite Tambopata spider is the little one that makes a model, in the middle of its web, of a big nasty spider, constructed from bits of debris. The little spider sits in the center of the big fake spider.
That sounded too interesting to ignore, I had to look that up :o

Indeed I found that this is the "sculpting" Cyclosa spider.

From the internet:

"The Peruvian spider creates decoys with legs placed downward, while the one in the Philippines displays its model with the legs splayed out in all directions."

https://www.dogonews.com/2014/3/10/craf ... -predators

Fantastic behaviour!

EDIT: here's a video showing the Cyclosa: https://www.youtube.com/watch?v=RrWnZ7VySac
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Lou Jost
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Post by Lou Jost »

I took some photos of it when I was in the Tambopata reserve, maybe I will put them up. They are not great photos.

Scarodactyl, thanks for the surprising reference about the electrical basis of spider ballooning!

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