Orb-weaver spider

Orb-weaver spiders or araneids are members of the spider family Araneidae. They are the most common group of builders of spiral wheel-shaped webs often found in gardens, fields and forests. "Orb" was previously used in English to mean "circular",[2] hence the English name of the group. Araneids have eight similar eyes, hairy or spiny legs, and no stridulating organs.[1]

The family is cosmopolitan, including many well-known large or brightly colored garden spiders. With around 3,100 species in 169 genera worldwide, Araneidae is the third-largest family of spiders (behind Salticidae and Linyphiidae).[1] Araneid webs are constructed in a stereotyped fashion. A framework of nonsticky silk is built up before the spider adds a final spiral of silk covered in sticky droplets.

Orb-webs are also produced by members of other spider families. The large golden orb-weavers (Nephilidae) and the long-jawed orb weavers (Tetragnathidae) were formerly included in the Araneidae; they are closely related, being part of the superfamily Araneoidea. The cribellate or hackled orb-weavers (Uloboridae) belong to a different group of spiders. Their webs are strikingly similar, but use a different kind of sticky silk.

Web[edit]

Argiope sp. sitting on the stabilimentum at the center of the web

Spiderlings in the web near where they hatched

Close-up of the cephalothorax on Eriophora sp. (possibly E. heroine or E. pustuosa

Generally, orb-weaving spiders are three-clawed builders of flat webs with sticky spiral capture silk. The building of a web is an engineering feat, begun when the spider floats a line on the wind to another surface. The spider secures the line and then drops another line from the center, making a "Y". The rest of the scaffolding follows with many radii of nonsticky silk being constructed before a final spiral of sticky capture silk.

The third claw is used to walk on the nonsticky part of the web. Characteristically, the prey insect that blunders into the sticky lines is stunned by a quick bite, and then wrapped in silk. If the prey is a venomous insect, such as a wasp, wrapping may precede biting.

Many orb-weavers build a new web each day. Most orb-weavers tend to be active during the evening hours; they hide for most of the day. Generally, towards evening, the spider will consume the old web, rest for approximately an hour, then spin a new web in the same general location. Thus, the webs of orb-weavers are generally free of the accumulation of detritus common to other species, such as black widow spiders.

Some orb-weavers do not build webs at all. Members of the genera Mastophora in the Americas, Cladomelea in Africa, and Ordgarius in Australia produce sticky globules, which contain a pheromone analog. The globule is hung from a silken thread dangled by the spider from its front legs. The pheromone analog attracts male moths of only a few species. These get stuck on the globule and are reeled in to be eaten. Interestingly, both types of bolas spiders are highly camouflaged and difficult to locate.

The spiny orb-weaving spiders in the genera Gasteracantha and Micrathena look like plant seeds or thorns hanging in their orb-webs. Some species of Gasteracantha have very long, horn-like spines protruding from their abdomens.

One feature of the webs of some orb-weavers is the stabilimentum, a crisscross band of silk through the center of the web. It is found in a number of genera, but Argiope, the yellow and banded garden spiders of North America, is a prime example. The band has been hypothesized to be a lure for prey, a marker to warn birds away from the web, and a camouflage for the spider when it sits in the center of the web. However, recent research suggests the stabilimentum actually decreases the visibility of the silk to insects, thus making it harder for prey to avoid the web.[3] The orb-web consists of a frame and supporting radii overlaid with a sticky capture spiral, and the silks used by orb-weaver spiders have exceptional mechanical properties to withstand the impact of flying prey.[4]

During the Cretaceous, a radiation of angiosperm plants and their insect pollinators occurred. Fossil evidence shows that the orb web was in existence at this time, which permitted a concurrent radiation of the spider predators along with their insect prey.[5][6] The capacity of orb–webs to absorb the impact of flying prey led orbicularian spiders to become the dominant predators of aerial insects in many ecosystems.[7] Insects and spiders have comparable rates of diversification, suggesting they co-radiated, and the peak of this radiation occurred 100 Mya before the origin of angiosperms.[8] Vollrath and Selden (2007) make the bold proposition that insect evolution was driven less by flowering plants than by spider predation – particularly through orb webs – as a major selective force.

Most arachnid webs are vertical and the spiders usually hang with their head downward. A few webs, such as those of orb-weavers in the genus Metepiera have the orb hidden within a tangled space of web. Some Metepiera are semisocial and live in communal webs. In Mexico, such communal webs have been cut out of trees or bushes and used for living fly paper.[citation needed] In 2009, workers at a Baltimore Wastewater Treatment Plant called for help to deal with over 100 million orb-weaver spiders, living in a community that managed to spin a phenomenal web that covered some 4 acres of a building with spider densities in some areas reaching 35,176 spiders per cubic meter.[9]

Peucetia viridana

Peucetia viridana is a green colored spider with cephalothorax having brown spots. The head region has a few spines and the centre has deep fovea which is green in colour. The clypeus is long with two black lines extending from the base of the middle anterior eyes. The sternum is heart shaped, pointed behind and covered with pines and hair. The legs are long and strong covered with conspicuous black spots and black long spines. The abdomen is long, narrowing behind and covered with fine hair. A longitudinal deep brown line runs through the center of the abdomen with lateral branches.[2]

The females are about 10-12 mm in size and the males about 8–10 mm in size.

It is generally found on grass and low shrubs.

Jumping Spider - Salticidae

The jumping spider family (Salticidae) contains over 500 described genera and over 5,000 described species,[1] making it the largest family of spiders with about 13% of all species.[2] Jumping spiders have some of the best vision among arthropods and use it in courtship, hunting, and navigation. Although they normally move unobtrusively and fairly slowly, most species are capable of very agile jumps, notably when hunting, but sometimes in response to sudden threats or crossing long gaps. Both their book lungs and the tracheal system are well-developed, and they use both systems (bimodal breathing). Jumping spiders are generally recognized by their eye pattern. All jumping spiders have four pairs of eyes with one pair being their particularly large anterior median eyes.

Distinguishing characteristics

Salticidae male anterior and dorsal aspects, showing positions of eyes

Jumping spiders are among the easiest to distinguish from similar spider families because of the shape of the cephalothorax and their eye patterns. The families closest to Salticidae in general appearance are the Corinnidae (distinguished also by prominent spines on the back four legs), the Oxyopidae (the lynx spiders, distinguished by very prominent spines on all legs), and the Thomisidae (the crab spiders, distinguished by their front four legs, which are very long and powerful). None of these families however, has eyes that resemble those of the Salticidae. Conversely, the legs of jumping spiders are not covered with any very prominent spines. Their front four legs generally are larger than the hind four, but not as dramatically so as those of the crab spiders, nor are they held in the outstretched-arms attitude characteristic of the Thomisidae.[3] In spite of the length of their front legs, Salticidae depend on their rear legs for jumping. The generally larger front legs are used partly to assist in grasping prey,[4] and in some species, the front legs and pedipalps are used in species-recognition signalling.

The jumping spiders, unlike the other families, have faces that are roughly rectangular surfaces perpendicular to their direction of motion. In effect this means that their forward-looking, anterior eyes are on "flat faces", as shown in the photographs. Their eye pattern is the clearest single identifying characteristic. They have eight eyes, as illustrated.[3][4] Most diagnostic are the front row of four eyes, in which the anterior median pair are more dramatically prominent than any other spider eyes apart from the posterior median eyes of the Deinopidae. There is, however, a radical functional difference between the major (AME) eyes of Salticidae and the major (PME) eyes of the Deinopidae; the large posterior eyes of Deinopidae are adapted mainly to vision in dim light, whereas the large anterior eyes of Salticidae are adapted to detailed, three-dimensional vision for purposes of estimating the range, direction, and nature of potential prey, permitting the spider to direct its attacking leaps with great precision. The anterior lateral eyes, though large, are smaller than the AME and provide a wider forward field of vision.

The rear row of four eyes may be described as strongly bent, or as being rearranged into two rows, with two large posterior lateral eyes furthest back. They serve for lateral vision. The posterior median eyes also have been shifted out laterally, almost as far as the posterior lateral eyes. They are usually much smaller than the posterior lateral eyes and there is doubt about whether they are at all functional in many species.

The body length of jumping spiders generally range from 1 to 25 mm (0.04–0.98 in).[3][5] The largest is Hyllus giganteus,[5] while other genera with relatively large species include Phidippus, Philaeus and Plexippus.[6]

In addition to using their silk for safety lines while jumping, they also build silken "pup tents", where they shelter from bad weather and sleep at night. They molt within these shelters, build and store egg cases within them, and also spend the winter in them.[7]

Habitat

Jumping spiders live in a variety of habitats. Tropical forests harbor the most species, but they are also found in temperate forests, scrub lands, deserts, intertidal zones, and mountainous regions. Euophrys omnisuperstes is the species reported to have been collected at the highest elevation, on the slopes of Mount Everest

Vision[edit]

The eight eyes of a Telamonia dimidiata located near the front

Marpissa muscosa, female

Jumping spiders have four pairs of eyes; three secondary pairs that are fixed and a principal pair that is movable.

The posterior median eyes (PME) are vestigial in many species, but in some primitive sub-families they are comparable in size with the other secondary eyes and help to detect motion.[9] While unable to form images, it is suspected that the reduced pair of eyes has a role similar to that of insect ocelli by receiving light from the sky. The photoreceptors in the other secondary pairs are almost exclusively greensensitive, but the PME have two visual pigments different from that in all the other eyes, sensitive to blue and UV-light.[10]

The posterior lateral eyes (PLE) are wide-angle motion detectors which sense motions from the side and behind. Combined with the other eyes, it gives the spider a near 360-degree view of the world.

The anterior lateral eyes (ALE) have the best visual acuity and are the most complex of the secondary eyes.[11] It has been shown that they are able to distinguish some details as well, and without them no "looming response" will be triggered by motion.[12] Even with all the other pairs covered, jumping spiders in a study could still detect, stalk and attack flies, using the anterior lateral eyes only, which are also sufficiently widely spaced to provide stereoscopic vision.[13]

The anterior median eyes (AME) have very good vision. This pair of eyes is built like a telescopic tube with a corneal lens in the front and a second lens in the back that focus images onto a four-layered retina, a narrow boomerang-shaped strip oriented vertically.[14][15] Physiological experiments have shown they may have up to four different kinds of receptor cells, with different absorption spectra, giving them the possibility of up to tetrachromatic color vision, with sensitivity extending into the ultraviolet range. As the eyes are too close together to allow depth perception, and the animals do not make use of motion parallax, they have evolved a method called image defocus instead. Of the four photoreceptor layers in the retina, the first two closest to the surface contain ultraviolet-sensitive pigments while the two deepest contain green-sensitive pigments. The incoming green light is only focused on the deepest layer, while the other one receives defocused or fuzzy images. By measuring the amount of defocus from the fuzzy layer, it is possible to calculate the distance to the objects in front of them.[16][17] In addition to receptor cells, also red filters have been detected, located in front of the cells that normally register green light.[18] It seems that all salticids, regardless of whether they have two, three, or four kinds of color receptors, are highly sensitive to UV light.[19] Some species (for example, Cosmophasis umbratica) are highly dimorphic in the UV spectrum, suggesting a role in sexual signaling (Lim & Li, 2005). Color discrimination has been demonstrated in behavioral experiments.

The principal, anterior median, eyes have high resolution (11 min visual angle),[20] but the field of vision is narrow, from 2 to 5°. The central region of the retina, where acuity is highest, is no more than six or seven receptor rows wide. However, the eye can scan objects off the direct axis of vision. As the lens is attached to the carapace, the eye's scanning movements are restricted to its retina through a complicated pattern of translations and rotations.[21] This dynamic adjustment is a means of compensation for the narrowness of the static field of vision. It is analogous to the way most primates move their eyes to focus images of interest onto the fovea centralis. Such movements within the jumping spider's eyes are visible from outside when the attention of the spider is directed to various targets.[22]

Behavior

Jumping spiders are generally diurnal, active hunters. Their well-developed internal hydraulic system extends their limbs by altering the pressure of body fluid (hemolymph) within them. This enables the spiders to jump without having large muscular legs like a grasshopper. Most jumping spiders can jump several times the length of their bodies. When a jumping spider is moving from place to place, and especially just before it jumps, it tethers a filament of silk (or 'dragline') to whatever it is standing on to protect itself if the jump should fail.[7] Should it fall, for example if the prey shakes it off, it climbs back up the silk tether. Some species, such as Portia, will actually let themselves down to attack prey such as a web spider apparently secure in the middle of its web. Like many other spiders that leave practically continuous silk trails, jumping spiders impregnate the silk line with pheromones that play a role in social and reproductive communication, and possibly in navigation.

Certain species of jumping spiders have been shown by experiment to be capable of learning, recognizing, and remembering colors, and adapting their hunting behavior accordingly.[23]

Hunting

The hunting behaviour of the Salticidae is confusingly varied compared to that of most spiders in other families.[24] Salticids hunt diurnally as a rule, which is consistent with their highly developed visual system. When it detects potential prey, a jumping spider typically begins orienting itself by swivelling its cephalothorax to bring the anterior median eyes to bear. It then moves its abdomen into line with its cephalothorax. After that, it might spend some time inspecting the object of its attention and determining whether a camouflaged or doubtful item of prey is promising, before it starts to stalk slowly forward. When close enough, the spider pauses to attach a dragline, then springs onto the prey.

There are, though, many variations on the theme and many surprising aspects. For one thing, salticids do not necessarily follow a straight path in approaching prey. They may follow a circuitous course, sometimes even a course that takes the hunter through regions from which the prey is not visible. Such complex adaptive behaviour is hard to reconcile with an organism that has such a tiny brain, but some jumping spiders, in particular some species of Portia, can negotiate long detours from one bush down to the ground, then up the stem of another bush to capture a prey item on a particular leaf. Such behaviour still is the subject of research.[24]

Some salticid species are continually on the move, stopping periodically to look around for prey, which they then stalk immediately. Others spend more time scanning their surroundings from one position, actively stalking any prey they detect. Members of the genus Phaeacius take that strategy to extremes; they sit on a tree trunk, facing downwards and rarely do any stalking, but simply lunge down on any prey items that pass close before them.[24]

Some Salticidae specialise in particular classes of prey. Ants comprise one such class. Most spiders, including most salticids, avoid worker ants, but several species not only eat them as a primary item in their diets, but also employ specialised attack techniques — Corythalia canosa for example, circles round to the front of the ant and grabs it over the back of its head. Such myrmecophagous species, however, will not necessarily refuse other prey items, and will routinely catch flies and similar prey in the usual salticid fashion, without the special precautions they apply in hunting dangerous prey such as ants. Ants offer the advantages of being plentiful prey items for which there is little competition from other predators, but it remains profitable to catch less hazardous prey when it presents itself.[24]

Some of the most surprising hunting behaviour occurs among the araneophagous Salticidae, and it varies greatly in method. Many of the spider-hunting species quite commonly will attack other spiders, whether fellow salticids or not, in the same way as any other prey, but some kinds resort to web invasion; nonspecialists such as Phidippus audax sometimes attack prey ensnared in webs, basically in acts of kleptoparasitism — sometimes they leap onto and eat the web occupant itself, or simply walk over the web for that purpose.

Salticidae in the genera Brettus, Cyrba, Gelotia, and Portia display more advanced web-invasion behavior. They slowly advance onto the web and vibrate the silk with their pedipalps and legs. In this respect, their behaviour resembles that of the Mimetidae, probably the most specialised of the araneophagous spider families. If the web occupant approaches in the manner appropriate to dealing with ensnared prey, the predator attacks.[24]

The foregoing examples present the Salticidae as textbook examples of active hunters; they would hardly seem likely to build webs other than those used in reproductive activities, and in fact, most species really do not build webs to catch prey. However, exceptions occur, though even those that do build capture webs generally also go hunting like other salticids. Some Portia species, for example, spin capture webs that are functional, though not as impressive as some orb webs of the Araneidae; Portia webs are of an unusual funnel shape and apparently adapted to the capture of other spiders. Spartaeus species, on the other hand, largely capture moths in their webs. In their review of the ethology of Salticidae, Richman and Jackson speculate on whether such web building is a relic of the evolution of this family from web-building ancestors.[24]

In hunting, Salticidae also use their silk for a tether to enable them to reach prey that otherwise would be inaccessible. For example, by advancing towards the prey to less than the jumping distance, then retreating and leaping in an arc at the end of the tether line, many species can leap onto prey on vertical or even on inverted surfaces, which of course in a gravitational field would not be possible without such a tether.

Having made contact with the prey, hunting Salticidae administer a bite to inject rapidly acting venom that gives the victim little time to react.[25] In this respect, they resemble the Mimetidae and Thomisidae, families that ambush prey that often are larger than the predator, and they do so without securing the victim with silk; they accordingly must immobilise it immediately and their venom is adapted accordingly.

Source: Wiki

Spider - Argiope

The genus Argiope includes rather large and spectacular spiders that often have a strikingly coloured abdomen. These spiders are distributed throughout the world. Most countries in tropical or temperate climates host one or more species that are similar in appearance. The etymology of the name is from a Greek name meaning "silver-faced."

Common names

Writing spider in South Carolina

In North America, Argiope aurantia is commonly known as the black and yellow garden spider, zipper spider, corn spider, and writing spider, because of the similarity of the web stabilimenta to writing.

In England, Argiope bruennichi, where it is found only on the southern coast, and in other parts of Europe, including Germany, is also known as the wasp spider. In Australia, Argiope keyserlingi and A. aetherea are known as St. Andrew's Cross spiders, for their habit of resting in the web with legs outstretched in the shape of an X, the cross of St. Andrew. The large white zigzag in the centre of its web is called the stabilimentum or web decoration.

The East Asian species Argiope amoena is known in Japan as kogane-gumo. In the Philippines, they are known as gagambang ekis ("X spider", again due to the stabilementa), and gagambang pari ("priest spider", due to the spider's body resembling a priest's head with a mitre).

Web

The average orb web is practically invisible, and it is easy to blunder into one and end up covered with a sticky web. The very easily visible pattern of banded silk made by Argiope is pure white, and some species make an "X" form, or a zigzag type of web (often with a hollow centre). The spider then aligns one pair of its legs with each of the four lines in the hollow "X", making a complete "X" of white lines with a very eye-catching spider coloured bright yellow on a field of black or variegated red white and yellow stripes forming its centre.

The white patterns are called stabilimentum and reflect UV light. They have been shown to play a role in attracting prey to the web, and possibly to prevent its destruction by large animals. The centres of their large webs are often just under 1 metre above the ground, so they are too low for anything much larger than a rabbit to walk under.

The overtness of the spider and its web thus has been speculated to prevent larger creatures from accidentally destroying the web and possibly crushing the spider underfoot.

Other studies suggest that the stabilimenta may actually lead predators to the spider; species such as A. keyserlingi place their web predominantly in closed, complex habitats such as among sedges.

As Argiope sit in the centre of their web during the day, they have developed several responses to predators, such as dropping off the web, retreating to the periphery of the web, or even rapidly pumping the web in bursts of up to 30 seconds, similar to the motion done by the unrelated Pholcus phalangioides

Reproduction

The male spider is much smaller than the female, and unassumingly marked. When it is time to mate, he spins a companion web alongside the female's. After mating, the female lays her eggs, placing her egg sac into the web. The sac contains between 400 and 1400 eggs.

These eggs hatch in autumn, but the spiderlings overwinter in the sac and emerge during the spring. The egg sac is composed of multiple layers of silk and protects its contents from damage; however, many species of insects have been observed to parasitise the egg sacs.

Bite

Like almost all other spiders, Argiope are harmless to humans. As is the case with most garden spiders, they eat insects, and they are capable of consuming prey up to twice their size. A. savigny was even reported to occasionally feed on the small bat Rhynchonycteris naso.[3]

They might bite if grabbed, but other than for defense they do not attack large animals. Their venom is not regarded as a serious medical problem for humans; it often contains a library of polyamine toxins with potential as therapeutic medicinal agents.[4] Notable among these is the argiotoxin ArgTX-636 (A. lobata).

A bite by the black and yellow garden spider (Argiope aurantia) is comparable to a bee sting with redness and swelling. For a healthy adult, a bite is not considered an issue.

Though they are not aggressive spiders, the very young, elderly, or those with compromised immune systems should exercise caution just as one would around a beehive.

Source: Wiki

Trachelas Tranquillus

Spiders (order Araneae) are air-breathing arthropods that have eight legs and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other orders of organisms.[2] Spiders are found worldwide on every continent except for Antarctica, and have become established in nearly every habitat with the exceptions of air and sea colonization. As of November 2015, at least 45,700 spider species,[3] and 114 families have been recorded by taxonomists.[1] However, there has been dissension within the scientific community as to how all these families should be classified, as evidenced by the over 20 different classifications that have been proposed since 1900.[4]

Anatomically, spiders differ from other arthropods in that the usual body segments are fused into two tagmata, the cephalothorax and abdomen, and joined by a small, cylindrical pedicel. Unlike insects, spiders do not have antennae. In all except the most primitive group, the Mesothelae, spiders have the most centralized nervous systems of all arthropods, as all their ganglia are fused into one mass in the cephalothorax. Unlike most arthropods, spiders have no extensor muscles in their limbs and instead extend them by hydraulic pressure.

Their abdomens bear appendages that have been modified into spinnerets that extrude silk from up to six types of glands. Spider webs vary widely in size, shape and the amount of sticky thread used. It now appears that the spiral orb web may be one of the earliest forms, and spiders that produce tangled cobwebs are more abundant and diverse than orb-web spiders. Spider-like arachnids with silk-producing spigots appeared in the Devonian period about 386 million years ago, but these animals apparently lacked spinnerets. True spiders have been found in Carboniferous rocks from 318 to 299 million years ago, and are very similar to the most primitive surviving suborder, the Mesothelae. The main groups of modern spiders, Mygalomorphae and Araneomorphae, first appeared in the Triassic period, before 200 million years ago.

A herbivorous species, Bagheera kiplingi, was described in 2008,[5] but all other known species are predators, mostly preying on insects and on other spiders, although a few large species also take birds and lizards. Spiders use a wide range of strategies to capture prey: trapping it in sticky webs, lassoing it with sticky bolas, mimicking the prey to avoid detection, or running it down. Most detect prey mainly by sensing vibrations, but the active hunters have acute vision, and hunters of the genus Portia show signs of intelligence in their choice of tactics and ability to develop new ones. Spiders' guts are too narrow to take solids, and they liquefy their food by flooding it with digestive enzymes and grinding it with the bases of their pedipalps, as they do not have true jaws.

Male spiders identify themselves by a variety of complex courtship rituals to avoid being eaten by the females. Males of most species survive a few matings, limited mainly by their short life spans. Females weave silk egg-cases, each of which may contain hundreds of eggs. Females of many species care for their young, for example by carrying them around or by sharing food with them. A minority of species are social, building communal webs that may house anywhere from a few to 50,000 individuals. Social behavior ranges from precarious toleration, as in the widow spiders, to co-operative hunting and food-sharing. Although most spiders live for at most two years, tarantulas and other mygalomorph spiders can live up to 25 years in captivity.

While the venom of a few species is dangerous to humans, scientists are now researching the use of spider venom in medicine and as non-polluting pesticides. Spider silk provides a combination of lightness, strength and elasticity that is superior to that of synthetic materials, and spider silk genes have been inserted into mammals and plants to see if these can be used as silk factories. As a result of their wide range of behaviors, spiders have become common symbols in art and mythology symbolizing various combinations of patience, cruelty and creative powers. An abnormal fear of spiders is called arachnophobia.

Body plan

Spiders are chelicerates and therefore arthropods.[6] As arthropods they have: segmented bodies with jointed limbs, all covered in a cuticle made of chitin and proteins; heads that are composed of several segments that fuse during the development of the embryo.[7] Being chelicerates, their bodies consist of two tagmata, sets of segments that serve similar functions: the foremost one, called the cephalothorax or prosoma, is a complete fusion of the segments that in an insect would form two separate tagmata, the head and thorax; the rear tagma is called the abdomen or opisthosoma.[6] In spiders, the cephalothorax and abdomen are connected by a small cylindrical section, the pedicel.[8] The pattern of segment fusion that forms chelicerates' heads is unique among arthropods, and what would normally be the first head segment disappears at an early stage of development, so that chelicerates lack the antennae typical of most arthropods. In fact, chelicerates' only appendages ahead of the mouth are a pair of chelicerae, and they lack anything that would function directly as "jaws".[7][9] The first appendages behind the mouth are called pedipalps, and serve different functions within different groups of chelicerates.[6]

Spiders and scorpions are members of one chelicerate group, the arachnids.[9] Scorpions' chelicerae have three sections and are used in feeding.[10] Spiders' chelicerae have two sections and terminate in fangs that are generally venomous, and fold away behind the upper sections while not in use. The upper sections generally have thick "beards" that filter solid lumps out of their food, as spiders can take only liquid food.[8] Scorpions' pedipalps generally form large claws for capturing prey,[10] while those of spiders are fairly small appendages whose bases also act as an extension of the mouth; in addition, those of male spiders have enlarged last sections used for sperm transfer.[8]

In spiders, the cephalothorax and abdomen are joined by a small, cylindrical pedicel, which enables the abdomen to move independently when producing silk. The upper surface of the cephalothorax is covered by a single, convex carapace, while the underside is covered by two rather flat plates. The abdomen is soft and egg-shaped. It shows no sign of segmentation, except that the primitive Mesothelae, whose living members are the Liphistiidae, have segmented plates on the upper surface.[8]

Cotton Stainer Bug - Pyrrhocoridae

Pyrrhocoridae is a family of insects with more than 300 species world-wide. Many are red coloured and are known as red bugs and some species are called cotton stainers because their feeding activities leave an indelible yellow-brownish stain on cotton crops. A common species in parts of Europe is the firebug, and its genus name Pyrrhocoris and the family name are derived from the Greek roots for fire "pyrrho-" and bug "coris". Members of this family are often confused with, but can be quickly separated from, Lygaeidae by the lack of ocelli (simple eyes) on the top of the head.

The membrane of the forewing has one or two cells from which about 7-8 branching veins emerge that may have branches that fuse together (anastomose) while the main veins reach the margins of the wing. They have three tarsal segments. They can be very difficult to separate from some members of the family Largidae, which also share some of these characters and belong to the same super family. Largids tend to have the edge of the pronotum (the top of the first thoracic segment) rounded but the taxonomic feature for separating them is the found only in females; female largids have the sixth visible (actually the seventh) abdominal segment appearing to be split in the middle whereas female pyrrhocorids have this undivided.[1] A few bugs in the family Rhopalidae have similar colors (e.g., Corizus hyoscyami) but they have ocelli, as do lygaeids. The scutellum is small and triangular. The antennae are made up of four segments with the second segment longer than the third. The beak-like mouthpart or rostrum has four segments and tip reaches at least the base of the middle pair of legs. Some species have the wing reduced so that the abdomen is visible from above.[2] More detailed distinguishing features that are usually visible only under a microscope include a much reduced scent gland opening on the mid-thoracic segment. There are three sensory hairs or trichobothria on the abdominal segments 3 to 6 and two such hairs on the seventh segment.

Most species feed on seeds or fruits particularly of plants belonging to the Malvales but a few feed on rotting debris including dead animal matter. A few species are predatory; Raxa nishidai is a predator of another pyrrhocorid, Melamphaus faber while Antilochus coqueberti feeds on other bugs including Dysdercus cingulatus.[4] A few are important crop pests. One species Dysdercus suturellus is well known in the southern cotton growing regions of the United States while Dysdercus cingulatus occurs on cotton in tropical Asia. They damage cotton bolls by staining as well as by cutting the fibres.

The genus Myrmoplasta is found in the African and Oriental regions and is somewhat unique in having highly reduced wings and appearing ant-like or myrmecomorphic. Males and females differ in their foreleg morphology, but such sexual dimorphism is also found in a few other genera.

Source: Wiki

Metallic Shield Bug - Scutelleridae

Scutelleridae is a family of true bugs. They are commonly known as jewel bugs or metallic shield bugs due to their often brilliant coloration. They are also known as shield-backed bugs due to the enlargement of the last section of their thorax into a continuous shield over the abdomen and wings.[1] This latter characteristic distinguishes them from most other families within Heteroptera, and may lead to misidentification as a beetle rather than a bug. These insects feed on plant juices from a variety of different species, including some commercial crops. Closely related to stink bugs, they may also produce an offensive odour when disturbed. There are around 450 species worldwide.

Jewel bugs are small to medium-sized oval-shaped bugs with a body length averaging at 5 to 20 mm (0.20 to 0.79 in). They can easily be distinguished from stink bugs (Pentatomidae) because the shield-like enlarged last section of their thorax (known as the scutellum, Latin for "little shield") completely covers the abdomen and the wings.

Despite their resemblance to beetles, jewel bugs are hemipterans or true bugs. The scutellum is an extension of the thorax, unlike the elytra of beetles which are hardened forewings. As such, jewel bugs have four membranous wings underneath the scutellum in contrast to two in beetles.The scutellum in jewel bugs also does not have a division in the middle and thus does not 'split open' when they take flight like in beetles.

The heads of jewel bugs are triangular and the antennae have three to five segments. Like all heteropterans, jewel bugs are characterized by a segmented beak-like mouthpart (known as the rostrum) During feeding, jewel bugs inject proteolytic enzymes in their saliva into plants, digesting plant matter into a liquid form which they then suck up. The tarsus has three segments (tarsomeres).

Colors

Though some species are quite drab,[10] the most conspicuous jewel bugs are often brilliantly colored, exhibiting a wide range of iridescent metallic hues that change with the view angle.[6] The colors are the result of a combination of factors. Some species like Chrsyocoris stockerus and Scutellera nobilis display colors from multiple thin layers of pigmented chitin. The colors often change or become duller when the specimens are dried, due to the topmost chitinous layer becoming opaque and obscuring the colors of the bottom layer. The colors can be restored by moistening the surfaces with water.

Iridescence (or goniochromism) in jewel bugs like Poecilocoris lewisi are the result of structural coloration. Instead of pigments, the colors are caused by the interference, diffraction, or scattering of light by numerous tiny structures.

In Poecilocoris lewisi, multiple tiny conical protuberances around 900 nm in height and averaging at a diameter of 360 nm are scattered on the epicuticle. These structures affect light passing through them, producing their oily-looking blue sheen (known as the Tyndall effect or Mie scattering).

In other species like the African shield bug (Calidea panaethiopica), the dorsal cuticle is dotted with tiny regularly spaced hemispherical cavities. The depressions act like Bragg mirrors. When light hits the pitted surface, it gives off multiple reflections resulting in the distinctive two tone yellow-blue iridescence.

The colors and patterns on jewel bugs can vary significantly between instars and even within adults of a species.

Jewel bugs are also known to mimic the colors, patterns, and shape of other organisms for defensive purposes. An example is the yellow-spotted black Steganocerus multipunctatus which exhibits Müllerian mimicry with the tortoise beetle Chiridopsis suffriani.

Defenses

Like stink bugs, a vast majority of jewel bugs, both adults and nymphs, are also capable of releasing pungent defensive chemicals from glands located on the sides of the thorax.Typical compounds exuded by jewel bugs include alcohols, aldehydes, and esters.

Nymphs and adults often exhibit clustering behavior, being found in large numbers close to each other. This behavior is thought to have an evolutionary advantage. The more individuals present in an area, the stronger the odor of the chemicals released when the bugs are threatened. If this fails, stink bugs will react to threat by flying away or dropping to the ground