Eating Habits of the Wolf Spider
Eating Habits of the Wolf Sp >By Nicholas DeMarino
The quintessential spider spins a web on which she waits for prey to come to her. Thatβs not the case with wolf spiders, though. Theyβre active hunters who ambush and kill a wide variety of prey β some as larger or larger than themselves.
Active Eaters
Many spiders spin silken webs to passively capture prey, but wolf spiders donβt wait for dinner delivery. These spiders, members of the Lycosidae family, are active hunters who stalk and either corner or rush their prey. Most active outdoors at night, wolf spiders can travel great distances in pursuit of food and donβt usually settle into permanent homes or territories. Some species dig burrows to hide during the day β others hide in them until they can ambush prey β which they line or cover with silk. Although many spiders sport six to eight simple eyes of relatively similar size in a couple of rows, wolf spiders have eight eyes in three sizes arranged in three rows β all the better to see you with. Their touch receptors are also finely honed to detect motion, which helps with hunting.
Dinner Menu
Like many other families of spiders, wolf spiders are distributed across every continent except Antarctica. As such, their diet includes a litany of region- and climate-specific insects, other arachnids, and even reptiles and amphibians. The diet of a given species doesnβt necessarily match that of its brethren in other areas, but there are some general commonalities. Some species are smaller than one-tenth of an inch long, while others can grow to lengths in excess of 1 inch. Most wolf spiders eat a variety of large insects, including beetles and grasshoppers. Theyβll generally attack prey as large or even larger than themselves.
Circumstances
Because wolf spiders are nocturnal hunters, itβs natural to assume they primarily eat insects and other prey that are most active at night. Thatβs usually the case for wolf spiders who use burrows and other hiding spots to ambush their prey, but a hungry wolf spider can become quite a bit more resourceful. Theyβre not above scavenging or even more devious tactics. Although youth and kinship appear to be mitigating factors, wolf spiders will eat other wolf spiders, according to University of Cincinnati research published in 2003. Thatβs part of the reason youβll rarely encounter more than one or two wolf spiders in a given area. Among solitary adults, an interaction between wolf spiders usually results in mating or cannibalism β or sometimes both β regardless of whether other food sources are readily available.
Venomous Consequences
Wolf spiders produce venom, which they inject via their fang-tipped jaws, called chelicerae. When these spider pounce on their prey, they envenom them β paralyzing or, more often, killing the animal. Wolf spiders immediately begin consuming their meal after this. Although theyβre not typically aggressive toward people, they will bite if cornered or handled roughly. Fortunately, though, wolf spider venom isnβt particularly harmful to humans. Many a brown wolf spider has been confused for a brown recluse, though, leading to confusion and panic.
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Controlling Garden Insects with Spiders
Iβm Gwen Outen with the VOA Special English Agriculture Report.
Spiders kill more insects than they can eat. And most spiders can eat up to two times their body weight in insects each day. So, if you want to keep harmful insects out of your garden, invite a few spiders to live there.
That was the advice given some years ago in the magazine Organic Gardening, published by the Rodale Institute. Spiders do eat both good and bad insects. But Professor Susan Riechert at the University of Tennessee in Knoxville said spiders eat more harmful insects than helpful ones.
Professor Riechert said spiders will remove from sixty to eighty percent of the insects from a garden. But, she added, if you want spiders to live in your garden, you must not use chemicals that can kill them.
Here are short descriptions of nine different kinds of spiders that live in gardens.
Orb weaver spiders make huge sticky webs between plants. When an insect enters the web and is trapped, the spider attacks.
Sheet-web weavers make flat webs. The spiders stays under the web. When an insect lands on top of the web, the spider reaches up and pulls the insect through to the bottom.
Mesh-web weavers make tiny webs inside small openings in a plantβs skin. This spider eats mainly aphids.
Combfooted spiders trap insects in their webs. Then they wrap their catch inside more web material.
Funnel-web weavers build circular webs that are wide at the top and closed at the bottom. When an insect lands on the web, the spider jumps out, catches the insect and drags it back inside the funnel to eat it.
Wolf spiders do not use webs to trap insects. They live on the ground among the leaves. They eat aphids, leafhoppers, flies, beetles and grasshoppers.
Jumping spiders also do not make webs. Their meal might include a spotted cucumber beetle, a corn earworm, or a bottom bollweevil.
Lynx spiders will spin some silk to seize an insect. But they, too, do not make a web. They like to eat fire ants.
Crab spiders move sideways, just like crabs in the sea. Crab spiders do not make webs. They wait quietly for an insect to come near and then they capture it.
Internet users can get more information about Organic Gardening magazine on the Web at organicgardening dot com. (organicgardening.com)
This VOA Special English Agriculture Report was written by Bob Bowen. Iβm Gwen Outen.
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The Carnivorous Diet of a Tarantula
Animals & Nature
Tarantulas are carnivores. They eat all kinds of insects, especially larger ones like crickets, grasshoppers, June beetles, cicadas, millipedes, caterpillars, and other spiders. Larger tarantulas will also eat frogs, toads, small rodents, lizards, bats, and small snakes. A South American species, the Goliath birdeater, is known to eat small birds as well, although this makes up only a small part of their diet.
How Tarantulas Catch and Eat Their Prey
Like other spiders, tarantulas cannot eat their prey in solid form. When a tarantula captures a live meal, it first bites the prey with its sharp fangs, also known as the chelicerae, and then injects it with a paralyzing venom. Once the prey is immobilized, the tarantula secretes digestive enzymes that liquefy the prey. The fangs are also used to chew or break down the prey, along with sharp, jagged plates that are located near the fangs that can also aid in cutting or crushing food. The spider then sucks up its meal using straw-like mouthparts under its fangs.
A tarantula has a βsucking stomach.β When the sucking stomachβs powerful muscles contract, the stomach size increases, creating a strong sucking action that permits the tarantula to suck its liquefied prey up through the mouth and into the intestines.
Once the liquefied food enters the intestines, it is broken down into particles small enough to pass through the intestine walls into the bloodstream, where it is distributed throughout the body. After feeding, the leftovers are formed into a small ball by the tarantula and thrown away.
Where Tarantulas Hunt
Some genera of tarantulas hunt prey primarily in trees; others hunt on or near the ground. All tarantulas can produce silk; while tree-dwelling species typically reside in a silken βtube tent,β terrestrial species line their burrows with silk to stabilize the burrow wall and facilitate climbing up and down.
Tarantulas Are Prey Too
Tarantulas look scary, but they also are objects of predation. The most specialized predator that likes to feast on tarantulas is actually an insect: a large member of the wasp family, Hemipepsis ustulata, also known as a βtarantula hawk.β The largest tarantula hawks track, attack, and kill large tarantulas.
Tarantula hawks use scent tracking to find the lair of a tarantula. To capture the spider, the wasp must deliver a sting to the spiderβs underside, exploiting the thin membrane between the leg segments. The sting paralyzes the spider, and then the wasp drags it back into its burrow and deposits an egg on the spiderβs abdomen. The wasp then seals the spider in its burrow and flies off to search for more food. The wasp larva hatches and feeds on the spiderβs nonessential parts and, as it approaches pupation, it consumes the remainder.
Giant centipedes and humans are also known to prey on tarantulas. Tarantulas are considered a delicacy by certain cultures in Venezuela and Cambodia. They can be roasted over an open fire to remove the hairs, which can otherwise cause an itch or skin irritation to humans, and then they are eaten.
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What Do Sp > Hussain Kanchwala 4 months ago
Spiders are part of a group called arachnids and are found in most places on Earth, except Antarctica. They have eight legs and two body parts: the cephalothorax and abdomen. There are thousands of spider species and their diet varies widely, largely dependent on their environment and size. For simplicity, we will generalize the diet of these species, but note that this generalization might not be fully accurate for all spider species. That being said, studies thus far on spiders have shown that the majority of species have similar dietary and digestive mechanisms with just a few variations based on the environments in which they live.
Sp >So, what do spiders like to eat? Thanks to Hollywood movies, many of us suffer from paranoia of getting bitten by a spider and dying some tragic death wrapped in a web. However, itβs important to note that humans are not a food source for these diminutive eight-legged creatures. With that being said, letβs now look into more detail about the preferred food choices of spiders.
Spider preying on insect (Image Credit: Flickr)
The diet of a sp >
Spiders donβt usually dine on plants and cannot eat solid food directly. They need to liquify their food before ingesting it, and their digestive system is not designed to digest the cellulose of plants. Recently, however, a spider species called Bagheera kiplingi was discovered in Central America whose primary food source is plant material! This plant-eating spider species dwell on the Acacia tree and feeds on the nectar the tree provides. The digestive system of these spiders can process sugar, proteins and even some fats, but whether or not they can digest cellulose remains a matter of further investigation and studies.
Bagheera kiplingi (Photo Credit : Maximilian Paradiz/Wikimedia Commons)
Some spiders can be described as βfussy eatersβ, as they are very selective and only confine their diet to a particular type of prey. For example, Lampona, a white-tailed spider, only prefers to eat other spiders. They rarely go beyond foraging for insects other than spiders. Lampona are sometimes even successful in trapping elusive long-legged spiders like Pholcus.
Lampona cylindrata (Image Credit: Flickr)
Interestingly, many sp >
Cannibalism
Although spiders are generally solitary creatures, if two disparate species move into close proximity, the more voracious of the two may cannibalize the other.
While female sp >
We studied a great deal about what sp >
Despite this conservative behavior in terms of water, some sp >
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What Spiders Eat
This page outlines the kinds of things most spiders eat and how they ingest and digest their food and excrete any waste materials.
But one kind of food that spiders normally do not eat is plant material. The reason for this is that they have to liquify their food before they can ingest it and are no more able to digest the cellulose of plants than we are. Not so long ago there was a flurry of interest in the popular media over the discovery that the Central American salticid, Bagheera kiplingi, seems to be the worldβs only known plant-eating spider. It had been observed that this species lives on a species of Acacia tree and feeds on nectar and especially on tiny specialized leaf tip structures called Beltian bodies. These contain useful amounts of sugars, proteins and some fats and hence can be broken down by the spiderβs digestive secretions to a liquid form the spider can ingest. Whether or not this salticid can digest the cellulose components of the Beltian bodies is presently unclear but if they can do so it may be with the help of an ant species that also lives on this Acacia species and seems to interact with B. kiplingi in a mutually beneficial manner.
The majority of spiders prefer a solitary life and readily cannibalize each other if forced into close proximity. Victims of this tendency even include the male of the same species unless he is very cautious, has leg spurs to keep the female at bay while mating, or is so much smaller than his female counterpart as to go almost unnoticed by her. While some adult female spiders display a small amount of maternal behaviour towards their newly hatched spiderlings it is very common for many individuals that hatch out of a single batch of spider eggs to be eaten either by the adult female or even by the stronger siblings in that hatching. And of course, spiders must always be cautious around those of a different species, especially ones with long legs or robust fangs since these are likely to win any battle that ensues.
Some spiders could be described as fussy eaters in that they have a very restricted range of prey they are willing to eat. The so-called white tailed spider, Lampona, is said to be an obligate araneophage (spider eater), which means it rarely, if ever, feeds on creatures other than spiders. Inside houses it certainly seems to be very happy to play a role in keeping the numbers of other spiders down and it also is proficient at ambushing bark spiders in the bush whenever the opportunity arises. Lampona sometimes even succeeds in capturing βimpossibleβ prey such as Pholcus, the daddy-long-legs spider.
Similarly, salticids belonging to the genus Myrmarachne are excellent mimics of ants and prefer to feed exclusively on them if possible. To facilitate this they have developed an ant-like external appearance that allows them to join a stream of foraging ants without alarming them. But some spiders, including Hadrotarsine theridiids such as Phycosoma, seem to prefer ants as prey even though they do not have an ant-like disguise. The magnificent spider, Ordgarius magnificus, uses a very different kind of disguise: it has learned how to suspend a droplet of fluid containing a pheromone attractant matching that of a particular species of moth, which therefore becomes a major part of its diet.
What anatomical structures does a spider use for ingesting and digesting food?
Many people worry about being bitten by spiders but the reality is that spiders do not have jaws like those of a savage dog and cannot actually bite anyone or any creature. Instead of conventional mandibles (jawbones) they use a pair of chelicerae on the ends of which are fangs that can penetrate human skin if they are long enough. These are helpful for grasping and immobilizing prey and are usually assisted by a scissor action of the chelicerae. On some spider species there are also strong teeth on the chelicerae that help the spider tear open its prey to provide access to its tissues and sometimes the palps and even the front legs and the spiderβs actual mouthparts also play a holding and crushing role.
The mouth opening is surrounded by the chelicerae in front and underneath the spider, a pair of maxillae on the sides, and a central labium. For most spiders there are fine hairs projecting inwards over the mouth entrance that strain solid particles out of any food the spider tries to ingest, only liquified materials actually entering the digestive system.
From the mouth the digestive tube passes backwards within the cephalothorax to a muscular expansion usually called the sucking stomach. This has a cross-section that can concertina and it has muscles attached to the roof and sides of the cephalothorax to increase its volume as well as encircling muscle bands that can compress it. Thus, it is able to drive fluid both forward and backwards by compression and suction. This arrangement allows the spider to pump digestive secretions into the captured prey and then to suck liquified food back into itself.
Present evidence indicates that spiders lack conventional salivary glands, these probably having evolved as venom glands. It is possible that some species have other simple enzyme-secreting glands that secrete near the oral opening but these seem to be relatively unimportant. In the more primitive mygalomorph spiders the salivary glands are confined to the chelicerae but in araneomorphs they typically extend into the front part of the cephalothorax. They may still secrete some digestive enzymes but the major source of these are almost certainly the midgut which is the part of the abdominal digestive system posterior to the sucking stomach.
Immediately behind the sucking stomach the digestive tube becomes the midgut and expands into a number of blind pouches called caeca. These sometimes take up a substantial amount of space in the cephalothorax and in some species even extend down into the coxae (the first segment of each leg). Similar but even more elaborate caeca are present in the abdomen, where they may occupy most of the space unless the spider is a gravid female, much of the available abdominal space then being taken up by a mass of eggs. The cells that form the walls of these caeca are secretory and in many respects the overall abdominal caecal mass is functionally and sometimes even visibly similar to the mammalian liver. It is believed to secrete digestive enzymes that the sucking stomach then expels onto or into the spiderβs prey and also completes the digestion of liquified food, releasing nutrients and water into the tissue spaces of both major parts of the spiderβs body. It may even parallel the mammalian liver in adding waste materials to the hindgut for excretion.
| What enzymes are important for digestion in spiders? Spiders seem to have relatively little use for carbohydrates though there is a significant amount of glucose in their haemolymph. Presumably this serves as a rapidly available energy source when this is needed. Unlike white ants spiders lack symbiotic microorganisms in their digestive systems to allow them to break down complex carboydrates such as cellulose. Of course, those species that forage in flowers may sometimes ingest nectar-containing water and are then likely to metabolize any sugars acquired in this manner. The normal prey of most spiders do not have large amounts of stored body fat, which suggests that lipids are also relatively unimportant components of a spiderβs diet. On the other hand, all cell membranes in animals contain lipids so spiders must either acquire lipids in their diet or make their own. Indeed, experiments with at least one spider species indicated that lipids are critical for maturation and ovarian development in the females. But spiders have a great need for proteins for silk spinning and other purposes and use proteolytic enzymes extensively for digestion. A variety of proteases, notably including collagenase, and probably some peptidases are used by spiders but some of these enzymes may only occur intracellularly in the gut caeca. |
How important is a supply of water for a spider?
Although spiders donβt have the same need to drink water regularly that we do they have often been observed to ingest water droplets they happen to find. More important water sources are the contents of their prey as well as water formed as a normal byproduct of metabolism. But despite this conservative behaviour, most spiders are at some risk of desiccation, this being particularly true for mygalomorph species. Thus, female mygalomorphs spend virtually their entire lives in a burrow where the humidity remains reasonably high and adult males venture above ground only at night and especially during and after periods of rain. Similarly, male funnel-web spiders are often found in swimming pools and laundries or near leaking garden taps, which shows they have an ability to respond to changes in atmospheric humidity and to seek out habitats where the humidity is high. Araneomorph spiders are generally more tolerant of desiccating conditions but the majority of them still prefer to stay out of the midday sun and to forage for insects among green foliage or during the evenings if in exposed habitats.
How does a spider dispose of any waste products derived from its food?
Unlike many insects, a spider does not produce copious amounts of faecal material because the indigestible parts of its prey do not enter its digestive system. Instead, they are discarded nearby. Burrow-dwelling mygalomorphs typically have the remains of insect exoskeletons scattered around their entrances and many web-building araneomorphs deposit strings of insect debris along strands of silk. However, all spiders do have a small amount of faecal material to dispose of from time to time. The posterior end of the digestive tube has an anal opening which is normally located just above (or behind) the spinnerets. Just before this opening is a blind sac called the cloaca or stercoral pocket and it is here that the spiderβs small amounts of insoluble wastes are stored until excretion is convenient. Spider βfaecesβ is usually whitish in colour because it also contains nitrogenous wastes, especially guanine, adenine, hypoxanthine and possibly uric acid, all of which are white. at least for some spider species there may also be some sequestration of waste materials on the inside surfaces of the exoskeleton, perhaps to be βexcretedβ when the spider moults.
Spiders lack the liver-bile system, kidneys and urinary bladder that mammals have so they cannot excrete unwanted materials in bile or a liquid urine. However, the abdomen does possess some delicate tubular structures called Malpighian tubules which drain directly into the stercoral pocket and which are believed to serve many of the same functions as the nephrons of mammalian kidneys.
How often must spiders eat?
The dietary habits of spiders are largely determined by the numbers and kinds of potential prey that happen to be in their vicinity. Unlike humans they do not require three meals a day every day. Instead, they are opportunistic eaters and will feed on as many insects as they can catch in one short period of time. There will be weeks when the insect population in their part of the world is so low they have no opportunities to feed at all. However, because they are poikilothermic (cold-blooded) and inactive for much of each day a temporary loss of a food supply is not a problem. On the other hand, prolonged periods of enforced starvation will ultimately lead to death. This is probably one of the reasons why mature adult females of many spider species, especially orb weavers, drop from their webs and die as winter approaches. But most mygalomorph species live much longer than just 12 months and avoid starvation during the winter months by simply retreating into their burrows and βhibernatingβ.
Can spiders store fuel the way a hibernating mammal does? To a small extent they probably can but those that live through several cold months in a what is effectiely the hibernated state seem to do so with no food intake and limited internal fuel reserves. Of course, some spiders paralyse their prey and wrap them in silk until they can be eaten conveniently but long-term food storage by this means does not seem to be common practice among spiders.
Some related sources of information
The pages on spider blood, spider venoms and spider growth and reproduction contain some information that is related to what is covered in the above paragraphs.
In addition, the website article by Robert Gale Breene III on spider digestion and storage is also worth reading.
Email Ron Atkinson for more information. Last updated 22 December 2018.
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