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Why do spiders make their web near the ceiling and near a light source?

Why do spiders make their web near the ceiling and near a light source?



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Why do spiders make their webs near the ceiling and near light sources ? Is their an advantage for spiders in doing that? For example do they catch more insects when their web is near a light source because prey insects are drawn to it, hence giving those spiders with a well-lit web a better chance of survival?


Because many insects (their food) are attracted to light. This attraction is called phototaxis.

Hypotheses for why insects are attracted to light

  1. The leading hypothesis for why so many insects are attracted to light is that before artificial existed, insects were using the light from the moon in order to navigate. They would keep themselves at a given angle relative to the light source in order to navigate straight.

  2. Another hypothesis is the presence of light indicates that the pathway is clear.

  3. A third hypothesis is that some insects may confuse artificial light source with the other sex. This appeared to be true for moths for example

These three hypotheses are not mutually exclusive.

How do spiders chose their habitats

For more information about the abilities of spiders to find a good habitat, have a look at this very interesting answer.


Why do orb-weaving spiders (Cyclosa ginnaga) decorate their webs with silk spirals and plant detritus?

To improve foraging success or to enhance survival, animals may give out false signals to mislead prey or predators. Web decorations are purported to be structures that some orb-weaving spiders build to transmit deceptive signals to their advantage. Cyclosa ginnaga incorporates a variety of silk (silk decorations) and plant materials (plant detritus decorations) into its webs as decorations. It has been hypothesized that web decorations are deceptive signals that either attract prey, provide protection through camouflage or act as a warning signal. Nevertheless, despite numerous studies on web decorations, their function has remained elusive because of conflicting results. Using a combination of field video recording and the quantification of colour contrasts in the visual systems of hymenopteran prey and passerine bird predators, we tested two functional hypotheses (prey attraction and predator defence) of two forms of web decorations (silk spiral and plant detritus) built by C. ginnaga. Silk-decorated, and to a lesser extent plant-decorated, webs intercepted more prey than undecorated webs, thus improving foraging success. This supports the prey attraction hypothesis however, we could not rule out the predator defence hypothesis because there was no predation on spiders observed for any web with or without decorations.


If You Must Kill That Spider, The Best Way Is To Freeze It

If we were all humane, nature-loving people, we would see a spider in our homes and simply smile, say hello, and let it go on its merry way. But we’re not. Many of us kill the spider. It’s okay you don’t have to admit to it right now. But the next time you come across an eight-legged visitor that you’d rather not be visit with, here’s the best way to kill it.

There probably is an infinite number of ways to kill a spider. The most common—but certainly not the best—is the “Hulk smash!” method. Find a blunt object, and bring it down upon that poor, unsuspecting arachnid, crushing it to death. The problem with this method, as anyone who’s tried it can attest, is that sometimes the spider doesn’t die. Maybe you miss. Maybe the spider is incredibly strong. Or maybe it scuttled out of the way before you could hit it. Plus, smashing is dangerous for your furniture and your paint job.

Some suggest killing the spider with fire. This is how Smarter Every Day dealt with an unwelcome Brown Recluse spider:

He explains the logic this way:

Burning a very small spider with an exoskeleton increases the pressure inside, and makes it explode… killing it instantly. It’s the quickest way to dispatch it that I could think of. I had the same thoughts…. which is why I burned it with fire.

The downside to the fire trick is that it’s messy. Plus, it could set your house on fire.

What about drowning the spider? That’s pretty cruel: it can take spiders over an hour to drown.

No, the best way to kill a spider, says Real Clear Science, is not with fire or water, but with ice. Dr. Jerome Rovner, a professor at Ohio State and a member of the American Arachnological Society, told RCS’s Newton blog:

Catch in an empty pill vial of appropriate size (or a baby-food-size jar), snap the cap on, and put it in the refrigerator freezer overnight. Getting cold is a normal experience of all spiders during winter, so it doesn’t seem cruel to knock them out by lowering their body temperature. The next day, pour enough rubbing alcohol in the container to submerge the frozen spider to insure that it will not recover from being frozen. The now dead spider and alcohol can then be poured into the toilet and flushed away.

So if you have to kill the spider, do it kindly and gently—in the freezer.

About Rose Eveleth

Rose Eveleth is a writer for Smart News and a producer/designer/ science writer/ animator based in Brooklyn. Her work has appeared in the New York Times, Scientific American, Story Collider, TED-Ed and OnEarth.


Cobweb spiders (Family: Theridiidae) make cobwebs

Literally, cobwebs are only old spiderwebs, but one family of spiders got the top title &ndash Theridiidae or &ldquocobwebs-spiders.&rdquo These home-abandoning spiders&mdashforming one of largest spider families, with over 3000 species&mdashget their name from their distinctly disorganized webs. Their tangled web formations don&rsquot have any discernible pattern. The different species have different disorganized patterns of web-building, but there are some overall commonalities.

A spider from the family Theridiidae weaving a cobweb (Photo Credit : Deepugn/Wikimedia commons)

Most are skilled hunters. They anchor their nets to support structures such as beams and wall corners, creating a three-dimensional noose. This noose then becomes a common nuisance in the home as soon as it serves its real purpose for the spider.

The ends of these nets, when active, have sticky droplets that stick unsuspecting insects like flies to the net. The same sticky property of the net also attracts dust and pollen, agents that tend to damage the net.


Identifying a Spider Egg Sac

Spider sacs or clutches are fairly easy to spot once you know what to look for. Unlike individual eggs which are usually too small to see, an egg sac is small but visible.

They can vary from a disk-like shape to fully round, although teardrop shapes are common. Coloration also varies by species, with light to dark shades of brown, grey, or a creamy white.

The clutch is actually a thick netting of spider silk designed to insulate and protect the eggs while they incubate.

Where do Spiders Lay Their Clutches?

This depends largely upon the type of spider. In the yard, they’re often located under fallen leaves and branches, in wood piles, tucked into burrows, or under the eaves.

Some spiders will also lay their eggs on tree branches away from ground predators. Hunting spiders will often lay the clutch near a potential food source. Some, like the wolf spider, actually carry their egg sacs wherever they go.

Indoors, you’ll most likely find the eggs in a relatively unused place, such as your attic or basement. Some spiders will lay their clutch under furniture, especially if you don’t regularly clean under the couch.

In most cases, you’ll find the sac tied into a corner where it has the most protection. Thus the underside of a cabinet where there’s edging is a good place to spot them.

Cars follow a similar rule to homes. The sacs will likely be in the engine compartment or trunk where it’s more insulated and away from human eyes. An RV or camper will have more places for the spider to hide her young, but even a motorcycle that hasn’t been used in a while can become an unwitting babysitter.

Depending upon the species you’re dealing with, spider eggs will be clutched either in spider webs, suspended from a surface, or webbed directly into a corner.

They’re more likely to produce a clutch in an area where an edible insect (flies, mosquitoes, grasshoppers, etc.) population exists but less likely to be where predatory insects such as wasps or centipedes are found.

Just How Many Eggs Does a Spider Lay?

Spiderlings are very fragile and most don’t make it far from the sac upon hatching. As a result, a female spider has the ability to produce several hundred eggs at once.

A black widow will typically lay 300 eggs. Meanwhile, the brown widow lays 120 to 150 eggs per sac and is capable of leaving up to 20 sacs during its short lifetime. A hobo spider on the other hand produces up to four egg cases with each case holding 50-100 eggs.

What Happens When the Eggs Hatch?

Spider egg sacs are designed to protect throughout the incubation period, which may last only a few weeks or an entire winter, depending upon the species.Upon hatching, the clutch of spiderlings break through the sac. At this point, they’re tiny and pale to almost translucent. They also move with incredible speed.

In most cases, the spiderlings will disperse by ballooning. They migrate to a high point and create a little silk parachute, then jump into the wind. If you remember the ending to Charlotte’s Web, this was what Charlotte’s children were doing at the end.

It takes about a year and several moltings for the spiderlings to fully mature, during which time most will be killed or eaten. However, any spiders still in your home when they mature will mate and further increase the infestation.


How to Get Rid of Spider Webs

Windows are one of spiders’ favorite ways to get into your home. After getting rid of your corner cobwebs, check out your windows. There’s a good chance you’ll find webs with and without spiders. Use your vacuum’s crevice tool to suck up whatever webs you can. Then grab a spray bottle of water or a hose.

Spiders often make webs in the corners of windows, between screens and windows and in other common hiding places. Spray down the window and screen from the inside with your water bottle. If you’re using a water hose, use the spray nozzle and soak the window and screen from the outside.

By spraying your windows, you get rid of more spider webs and send any spiders still hiding out on their way. Clean the window and wipe down screens with a cloth to remove any remaining residue from the spider webs.


Introduction

Some spiders from different families, such as Linyphiidae (sheet-weaver spiders), Araneidae (orb-weaving spiders), Lycosidae (wolf spiders), and Thomisidae (crab spiders), can disperse aerially with the help of their silks, which is usually called ballooning behavior [1–6]. There are 2 representative takeoff methods in ballooning flight: “tiptoe” and “rafting” [7–10]. If spiders perceive appropriate weather conditions for ballooning, they climb up to the highest position of a blade of grass or a branch of a tree and raise their abdomen as if standing on their tiptoes, in order to position the abdomen at the highest level, before spinning the ballooning lines. They release a single or a number of silks in the wind current and wait until a sufficient updraft draws their body up in the air. This is known as a “tiptoe” takeoff [9,10] (see S1 and S2 Figs). Another takeoff method is called “rafting,” in which spiders release the ballooning lines from a hanging position, relying on their drag line [7,8,10] (see S3 Fig). In these ways, some spiders can travel passively hundreds of kilometers and can reach as high as 4.5 km above sea level [11,12]. For example, one of the first immigrant species on new-born volcanic islands are known to be spiders [13–15]. Aerial dispersal of spiders is an influential factor on agricultural economy and ecology because spiders are highly ranked predators in arthropods and impact on a prey’s population [16]. Due to the spider’s incredible aerial dispersal ability, the physical mechanism of a spider’s flight has been questioned for a long time, not only in public media but also in scientific research [16–23].

Ballooning dispersal is efficiently used by spiderlings (young spiders, just a few days after eclosion from their eggs) to avoid cannibalism at their birth sites, which are densely populated by hundreds of young spiders, and to reduce competition for resources [23,24]. Some adult female spiders balloon to find a place for a new colony [4,25,26], and others balloon to search for food and mates [4,27]. Most of the ballooning spiders were spiderlings and spiders under 3 mm in length and 0.2–2 mg in mass [1–5,28,29]. Nevertheless, there are only a few reports on the ballooning of large spiders (over 3 mm in length, over 5 mg in mass) [4,5,25,26].

Spiders balloon most frequently during late spring and autumn seasons [2,4,30]. The influences of microclimates on ballooning—such as temperature, humidity, and wind conditions—have been extensively studied: (i) Many studies agree on a positive correlation of temperature [1,3,31] or a rapid increase in temperature [31–34] (ii) low humidity is favorable for spiders to balloon [1,32,34] (iii) for small spiders, 0.2–2 mm in length, the favorable mean wind speed is limited to 3 m s −1 at a level of 2 m [30,31,35]. The local favorable wind speeds were 0.35–1.7 m s −1 in experiments and 0.55–0.75 m s −1 in nature [1,3]. These values, however, differ for spiders of different sizes (between 0.78–1.21 mm) [1,36]. Recently, Lee and colleagues showed that not only the mean wind speed at a level of 2 m but also the local wind speed can be limited by a wind speed of 3 m s −1 for spiderlings [37]. Instability of atmosphere was pointed out as an influential factor [30,31,35]. Suter and Reynolds suggested a possible relation of spiders’ ballooning behavior with atmospheric turbulent flow [16,20].

There have been a number of models that have tried to explain spiders’ high buoyant capability (aerial dispersal capability): a fluid-dynamic lollipop model [17], a flexible filament model in turbulence [16], and an electrostatic flight model [22]. Recently, Zhao and colleagues implemented the 2-dimensional numerical simulation using an immersed boundary method, which can simulate the ballooning dynamics in more detail [38]. The result shows that the atmospheric instability enables longer suspension of a ballooner in the air, which agrees with the result of Reynolds’s simulation and suggests that a spider may sense the vibration of vortex shedding on the spider silk through their silk [16,38], which is an interesting hypothesis.

In spite of the abovementioned models and studies, dynamics in spiders ballooning are still not well understood, because of a lack of serious scientific observation studies and specific experiments. Many of the ballooning spiders are very small, with weights of 0.2–2 mg, which are difficult to study [1,3,36,37]. Many described experiments were not focusing on the spider’s ballooning behavior itself but assumed that spiders use a certain length of the drag line [18,19,21]. The ballooning of large spiders is also a struggle because (i) the observed physical properties of ballooning silks and spider size (60–80 cm long and 3–4 silk threads, 85–150 mg body weight) of an adult of Stegodyphus mimosarum seemed to be unrealistic for ballooning [25], because the required vertical speed of wind was 9.2–21.6 m s −1 , according to Henschel’s calculation [18,39] (ii) Humphrey’s model cannot explain the ballooning flight of spiders with a weight of over 9 mg, because of the mechanical properties of a spider silk [17]. The following questions are still to be answered: (i) How many and how long are the silk fibers needed for ballooning, especially in the case of large spiders with weights over 5 mg? (ii) Which silk fibers and glands are used for ballooning? (iii) How do ballooning silks shape during the flight? (iv) Do spiders control the buoyant capability by changing the length of silks or their pose during the flight? (v) Why do spiders usually balloon at a low wind speed (below 3 m s −1 )?

The aim of this paper is to offer behavioral clues and quantitative data in ballooning flight that may answer these questions. Therefore, we investigated the ballooning behavior of adult and subadult crab spiders (Xysticus spp., Thomisidae) that had a size of 3–6 mm and a weight of 6–25 mg. This observation of large spiders could provide a good basis for the physical characterization of ballooning. Additional experiments were performed in a wind tunnel for a precise documentation of ballooning silks and to analyze the details of ballooning behavior. Also, the aerodynamic environment on a flat grass field was measured to investigate the usable updraft for a ballooning flight.


SAMPLE SPIDER WEBS

Of course, there are some spiders that have distinct web styles. For others, including the &ldquoBig Three,&rdquo it&rsquos important to know what to look out for. With that in mind, we put together a few snapshots of some important and/or interesting spider webs worth knowing about. A large black-and-yellow arachnid, the yellow garden spider (Agriope aurantia, shown above) spins a web in open areas and creates the familiar spider web pattern, but adds its own twist to the classic design. A large black and yellow spider, you&rsquoll recognize its web by a unique zig-zag pattern found inside it. The purpose of this added touch is disputed &ndash some say it warns birds to avoid flying into the web, while others say it hides the spider from insects. These spiders are not aggressive and rarely bite. The black widow spider (Latrodectus mactans, shown above) weaves a tangled web to catch its prey, and once ensnared, the spider wraps it and bites it to inject its venom. After the venom takes effect, the spider carries its meal to a concealed area for consumption, so you may not see the black widow immediately. The black widow&rsquos silk is said to be exceptionally strong, a characteristic you may note when trying to brush it away with a broom. Black widow bites from mature females pose a serious threat to people, though deaths from their bites are exceptionally rare. Spinning a horizontal web, the venusta orchard spider (Leucauge venusta, shown above) is a long-legged arachnid with vibrant colors. It has green legs and a back that&rsquos dappled with whites, yellows, and blacks. Their webs hang in shrubs and trees and feature a widely-spaced spiral band. The spider will bite its prey and wrap it in silk. Mostly found in the western U.S. and Canada, the web of the hobo spider (Eratigena agrestis, shown above) is a funnel type and rarely found in human habitations. Instead, they prefer to set up their webs in fields. Generally not considered aggressive, it may become so if its eggs appear to be threatened. Scientists dispute just how toxic their venom is, so, just to be safe, steer clear of these spiders and their webs. Spiny-backed orb-weaver spiders (Gasteracantha cancriformis, shown above) can be found throughout the U.S., and they create spiral orb-style webs. Their most striking features are the crab-like spines protruding from its sides and their unique coloration patterns. Their bites are generally harmless to people. There are many kinds of grass spiders (Agelenopsis spp, shown above) and they weave a funnel web in bushes and grass. This web isn&rsquot sticky, but that doesn&rsquot matter to these fast-moving arachnids. As soon as they sense a vibration on their web, they scramble out of their funnel to make a kill. Their venom paralyzes insects and other arthropods but isn&rsquot known to harm humans.


Contents

When spiders moved from the water to the land in the Early Devonian period, they started making silk to protect their bodies and their eggs. [3] [5] Spiders gradually started using silk for hunting purposes, first as guide lines and signal lines, then as ground or bush webs, and eventually as the aerial webs that are familiar today. [6]

Spiders produce silk from their spinneret glands located at the tip of their abdomen. Each gland produces a thread for a special purpose – for example a trailed safety line, sticky silk for trapping prey or fine silk for wrapping it. Spiders use different gland types to produce different silks, and some spiders are capable of producing up to eight different silks during their lifetime. [7]

Most spiders have three pairs of spinnerets, each having its own function – there are also spiders with just one pair and others with as many as four pairs.

Webs allow a spider to catch prey without having to expend energy by running it down, making it an efficient method of gathering food. However these energy savings are somewhat offset by the fact that constructing the web is in itself energetically costly, due to the large amount of protein required in the form of silk. In addition, after a time the silk will lose its stickiness and thus become inefficient at capturing prey. It is common for spiders to eat their own web daily to recoup some of the energy used in spinning. Through ingestion and digestion, the silk proteins are thus recycled.

There are a few types of spider webs found in the wild, and many spiders are classified by the webs they weave. Different types of spider webs include:

  • Spiral orb webs, associated primarily with the family Araneidae, as well as Tetragnathidae and Uloboridae[8]
  • Tangle webs or cobwebs, associated with the family Theridiidae
  • Funnel webs, with associations divided into primitive and modern
  • Tubular webs, which run up the bases of trees or along the ground
  • Sheet webs

Several different types of silk may be used in web construction, including a "sticky" capture silk and "fluffy" capture silk, depending on the type of spider. Webs may be in a vertical plane (most orb webs), a horizontal plane (sheet webs), or at any angle in between. It is hypothesized that these types of aerial webs co-evolved with the evolution of winged insects. As insects are spiders' main prey, it is likely that they would impose strong selectional forces on the foraging behavior of spiders. [3] [9] Most commonly found in the sheet-web spider families, some webs will have loose, irregular tangles of silk above them. These tangled obstacle courses serve to disorient and knock down flying insects, making them more vulnerable to being trapped on the web below. They may also help to protect the spider from predators such as birds and wasps. [10] It is reported that several Nephila pilipes individuals can collectively construct an aggregated web system to defend birds predation from all directions. [11]

Orb web construction Edit

Most orb weavers construct webs in a vertical plane, although there are exceptions, such as Uloborus diversus, which builds a horizontal web. [12] During the process of making an orb web, the spider will use its own body for measurements. There is variation in web construction among orb-weaving spiders, in particular, the species Zygiella x-notata is known for its characteristic missing sector web crossed by a single signal thread. [13]

Many webs span gaps between objects which the spider could not cross by crawling. This is done by first producing a fine adhesive thread to drift on a faint breeze across a gap. When it sticks to a surface at the far end, the spider feels the change in the vibration. The spider reels in and tightens the first strand, then carefully walks along it and strengthens it with a second thread. This process is repeated until the thread is strong enough to support the rest of the web.

After strengthening the first thread, the spider continues to make a Y-shaped netting. The first three radials of the web are now constructed. More radials are added, making sure that the distance between each radial and the next is small enough to cross. This means that the number of radials in a web directly depends on the size of the spider plus the size of the web. It is common for a web to be about 20 times the size of the spider building it.

After the radials are complete, the spider fortifies the center of the web with about five circular threads. It makes a spiral of non-sticky, widely spaced threads to enable it to move easily around its own web during construction, working from the inside outward. Then, beginning from the outside and moving inward, the spider methodically replaces this spiral with a more closely spaced one made of adhesive threads. It uses the initial radiating lines as well as the non-sticky spirals as guide lines. The spaces between each spiral and the next are directly proportional to the distance from the tip of its back legs to its spinners. This is one way the spider uses its own body as a measuring/spacing device. While the sticky spirals are formed, the non-adhesive spirals are removed as there is no need for them any more.

After the spider has completed its web, it chews off the initial three center spiral threads then sits and waits. If the web is broken without any structural damage during the construction, the spider does not make any initial attempts to rectify the problem.

The spider, after spinning its web, then waits on or near the web for a prey animal to become trapped. The spider senses the impact and struggle of a prey animal by vibrations transmitted through the web. A spider positioned in the middle of the web makes for a highly visible prey for birds and other predators, even without web decorations many day-hunting orb-web spinners reduce this risk by hiding at the edge of the web with one foot on a signal line from the hub or by appearing to be inedible or unappetizing.

Spiders do not usually adhere to their own webs, because they are able to spin both sticky and non-sticky types of silk, and are careful to travel across only non-sticky portions of the web. However, they are not immune to their own glue. Some of the strands of the web are sticky, and others are not. For example, if a spider has chosen to wait along the outer edges of its web, it may spin a non-sticky prey or signal line to the web hub to monitor web movement. However, in the course of spinning sticky strands, spiders have to touch these sticky strands. They do this without sticking by using careful movements, dense hairs and nonstick coatings on their feet to prevent adhesion. [14]


  • The brown recluse spider will only bite when disturbed in their secluded spot. This could occur under furniture or beds.
  • It would be wise to shake out your clothing and shoes before dressing.
  • Inspect items before using. If the brown recluse infestation is heavy, seal clothing items and shoes in plastic bags.
  • Don't garden, handle firewood, pine straw, etc, without gloves.
  • Try to keep doors and windows screened and shut.
  • Minimize light from the outside. Lights attract insects, and the insects attract the spiders.
  • Don't go barefoot.
  • Remove beds from walls and curtaints, keeping bedspreads and bed skirts from touching the floor.
  • Lighten Up a room or let sun into the house.
  • Keep children and pets off of the floor away from dark cluttered areas.
  • Inspect bedding before getting into bed.
  • Eliminate as much clutter as possible in storage areas and frequently dust and vacuum around windows, corners of rooms, and under furniture.
  • Dust and vacuum thoroughly to remove dead insects, spiders, webs, and egg sacs.
  • Since brown recluse spiders stay hidden during the daytime hours in boxes, in furniture and other stored items, they can be easily transported. Check these boxes.

  • Brown recluse spider adults are soft-bodies, yellowish-tan to dark brown,uniform color.
  • 6 eyes most spiders have 8 eyes
  • Oval shaped abdomen
  • The adult body varies from 1/3-to 1/2 inch in length. With the legs it can be an overall size of 1 inch diameter or greater(Body not more than 1/2").
  • No spines on legs with long thin legs that are uniformly colored.
  • If the body is a different color than the legs, or if the legs have different colors, it is not a Brown Recluse spider. If there are more than one color on the abdomen, it is not a Brown Recluse
  • Brown Recluse spiders have only fine hairs if they have thick spines on their legs, they are not recluses.
  • The brown recluse spider has a distinctive darker brown violin-shaped mark, with the neck of the violin pointing towards the abdomen
  • Tail end has no markings.

Brown Recluse Spider Bites

People commonly get brown recluse spider bites in areas that the spiders had been hidiing in shoes, stored towels, the old work shirt in the shed, etc.
It is very common to get a brown recluse spider bite when you are changing clothes, putting your hands into a pocket, or putting on shoes. The brown recluse spider had crawled in there at some time to take shelter. The Brown Recluse commonly bites when it is disturbed by being squeezed.

The initial pain with the brown recluse spider bites is not intense, unless there is a severe reaction. Within 8 to 12 hours the pain from the brown recluse spider bite becomes intense. Within 24 to 36 hours, the victim may have a fever,chills, nausea, joint pain or be restless. The area of the brown recluse spider bite enlarges, becomes inflamed and the tissue is hard to touch.

The venom of this spider has an enzyme that destroys cell membranes in the wounded area. The affected tissue sloughs away, exposing underlying tissues. and over a period of a few days a large ulcerous sore forms.

An open wound from the brown recluse spider bite may range form the size of an adult's thumbnail to the span of a hand. The sore heals very slowly (6-8 weeks) and often leaves a large, disfiguring scar.

If bitten, collect the spider if possible for identification get medical attention immediately.

Apply ice packs to relieve the swelling in the brown recluse spider bite area.

National Hotline Poison Center : 1-800-222-1222