Is it randomn or do they analyze environment?
In: Biology
Airflow! It varies a bit from species to species but your archetypical spiral or wheel web is often placed using airflow.
The spider starts by letting out a thin little guideline with a sticky end and letting it flow on the wind. As the spider lets the line get longer and longer, it’ll catch on a surface somewhere, like a nearby branch.
Now the spider can cut the guideline and attach the end it’s holding end to the surface it’s sitting on. This provides a taut line between two spots in a place with good airflow. Then the spider proceeds to ~~draw the rest of the owl.~~ weave the rest of the web by going back and forth creating guidelines over the gap it bridged before filling out the web.
The airflow bit is significant here. It doesn’t just make it easy to get a line across a gap. Flying insects follow airflows like a surfer riding a wave. So this method of selecting a place to weave a web is a good way of getting it exactly where bugs will be flying.
That said, spiders weave far more webs than people think. Webs often don’t last more than hours or a few days at most. Maybe the weather destroys it or the plants move in the wind ripping it apart. An animal moves through it. Or the web has been used and repaired too many times to be worth the maintenance. And sometimes a web just proves to be in a bad spot. A spider won’t just sit there and starve, if a location doesn’t yield prey, they will abandon it and weave a web elsewhere.
But there’s plenty of web types that work differently. A sheet web is a horizontal sheet of silk between tall blades of grass. The spider will stretch strong, springy lines above the sheet. When insects jump or fly up from the grass, they’ll hit the springy trip lines and be bounced into the waiting sheet web.
But it can get way crazier than that. Net spiders don’t attach their web to their environment. They weave a net that they carry around and throw at their prey. The bolas spider makes sticky balls at the end of a line and then expertly swings this bolas to knock flying insects out of the sky.
One of my favourite spiders weaves an underwater web. [Not to catch prey, it uses its web like a net and then brings down air bubbles into the net to create a diving bell where it can sit underwater](https://news.bbcimg.co.uk/media/images/53114000/jpg/_53114911_5argyronetaaquaticaeatingwaterfleainbubble2011-014110.jpg)and watch its surroundings. When it spots prey, it’ll swim out and catch bugs or even a small fish and then drag it back into its big air bubble where it can breathe and eat.
They analyze their environment to some degree.
For example there are various kinds of crab spiders that will hide in flowers, but they choose those flowers that resemble their own color and that are attracting the most bees (higher up, currently blooming, etc)
Similarly web building spiders will often choose dark places with a small air draft, for example your basement window.
They will instinctively place their spider webs in locations where it is common for insects to fly into them. Quite often over openings, especially between light and dark areas.
By careful calculation of their surroundings. They look at environmental factors such as direction of light and airflow to determine where their target species might travel and intercept it. If they don’t catch anything within a given time they make a “sail” web and fly to a new promising location.
I read that spiders can eat their own web if they can’t find food (or if they place their web in a location that doesn’t provide food). This is sometimes seen when you see a spider crawling straight up a random web strand. They latched on to one end and broke it, then gravity took them down and they eat thy webbing which allows them to re-secrete it, with more stickiness. They will usually do two or three strands to see what they can catch. If nothing, they eat it and move on. If they catch something, this shows the spider they chose wisely and after eating (poisoning and drinking their victim) they are able to produce more webbing and fill in the gaps and make a larger web. When you see a spider “web” this is because the spider caught something and determined this was a good location to stay. I have a huge spider that chills in the corner of my garage door and that thing eats more flies than anything I have even seen. He’s fat and functional (and although my wife dislikes him) he is an earner and welcome in my garage.
Why does it seem that in the morning they seem to go away
I remember at my childhood home it would be up when I was playing basketball at night with the floodlight on outside
Then in the morning it was gone
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