Cyrtophora citricola, also known as the tropical tent-web spider, is an orb-weaver spider in the family Araneidae. It is found in Asia, Africa, Australia, Costa Rica, Hispaniola, Colombia, and Southern Europe and in 2000, it was discovered in Florida. C. citricola differs from many of its close relatives due its ability to live in a wide variety of environments. In North America and South America, the spider has caused extensive damage to agricultural operations.
C. citricola is in the orb web spider family, but its orb webs are considered atypical. They have a thick silk strand barrier above the orb and a thinner barrier below the orb. This gives the webs a horizontal mesh-like appearance. The spider has developed distinct and specific prey-capturing techniques using its unconventional webs. The prey flies into the upper mesh layer of the web and is deflected into the orb web. The spider then collects and stores the prey in its web. The difference in C. citricola's web silk stems from physiological variations in its spinning apparatuses, as compared to other closely related species. Its webs are non-adhesive and do not require daily respinning.
This spider is one of the few species to exhibit a variable level of sociality. C. citricola can be seen in colonies, which may have arisen due to reduced predation. Within these colonies, each spider has its own web that is linked to other spiders through communal webbing. The spider webs are often built in large matrices next to one another and can span entire trees. The spider usually peacefully coexists with other spiders in the colony. However, at times the spider may have to ward off other spiders in the colony that may try and claim its web.
C. citricola is nocturnal, only performing necessary tasks during the day. During the day, it remains idle and tries to stay out of sight from predators. Most of its foraging and prey capture happen at night.
C. citricolas color and size can vary greatly. Many spiders sport a black and white pattern while others are brown. Males often appear black. Male and female spiders have a sexual dimorphism. The body length in females normally reaches , while males are only long.
Taxonomy
Peter Forsskal discovered Cyrtophora citricola in the Arabian Peninsula during his Yemen expedition, sometime between 1761 and 1763. He first saw the spiders in citrus trees and described their horizontal webs as nets. The spider's common name, "tropical tent-web", derives from these observations. Upon Forsskal's death of malaria in 1763, his manuscripts, which included details of the spider, were collected and sent from Yemen back to Denmark by his friend Carsten Niebuhr. These records were published in 1775 as Descriptiones animalium, avium, amphibiorum, piscium, insectorum, vermium; the spider appeared under the name Aranea citricola.
C. citricola was classified in the Araneidae family because it creates orb-webs. Between 1776 and 1864, the spider was classified under the genus Epeira, a synonym for Aranea, more commonly known as Araneus. The spider was moved from the genus Aranea to the genus Cyrtophora by Eugene Simon in 1864 – a decision made because its webs were so different from those constructed by other spiders in the genus Aranea. C. citricola webs are horizontal and tent-shaped, similar to those of other spiders in the genus Cyrtophora. Like other members of Cyrtophora, C. citricola's 2nd, 3rd, and 4th pairs of legs have a shorter combined patella and tibia length than the femurs on the same legs. Additionally, it shares the same eye pattern where the posterior eye row is recurved: a typical genus-defining trait. C. citricola has broader cephalic structures than other orb-web spiders in the genus Manogea.
Phylogeny Cyrtophora citricola falls into the family Araneidae because of three characteristics. The male's palpal faces the mesial, or midline of the body. The male spider's palpal has an exoskeleton on their bulbous known as a radix, and the spider has a thin reflective layer of tissue in the posterior set of its eyes called the tapetum. C. citricola differs from "derived araneoids", which are a part of the superfamily Araneoidea, such as Theridion and Linyphiidae, because it lacks smaller aciniform spigots in their median spinnerets. These spigots each individually produce a strand of aciniform silk, the strongest type of spider silk.
C. citricola is a part of the argiopoid clade because there is a sexual dimorphism between males and females. Female are larger than males. The sexual dimorphism present in C. citricola separates them from members of the Araneinae subfamily including Nuctenea, Cyclosa, and Mangora. C. citricola is a part of the Cyrtophorinae subfamily and shares the sexual dimorphism trait with the Argiopinae, Gasteracanthinae, and Micratheninae subfamilies. Within the argiopoid clade, C. citricola is a member of the argiopine clade because the upper section of its exoskeleton is hairy. This trait distinguishes C. citricola from the Gasteracanthinae and Micratheninae subfamilies. Within the argiopine clade, C. citricola is a member of the Cyrtophorinae family, which includes the genera Cyrtophora and Manogea. Cyrtophorinae's subfamily defining features are its embolus, the palpal bulb's open duct, running in a counterclockwise direction, and its non-adhesive orb-webs.
Description Cyrtophora citricola occurs in various colors and may have different colored spots on the abdomen. The spider is sexually dimorphic. Females may reach 10 millimetres (0.39 in) long and are larger than their male counterparts who are usually 3 millimetres (0.12 in) long. C. citricola's legs are different lengths with legs I and II being the longest. In Florida, male spiders are black, while females can change the color of their abdomens to match their surroundings and can camouflage in their webs. The females have white trichobothria. In Turkey, they usually appear brown with grey hair.
C. citricola has a distinctive horizontal bifurcation at the posterior abdomen. C. citricola is different from its other relatives because it has two pairs of dorsal tubercles and a pair of posterior tubercles. C. citricola typically has seven denticles. The opisthosoma has two dorsal pairs of protuberances and two posterior lobes. C. citricola has two rows of eyes. The largest eyes are the two median eyes in the anterior row. In some places, C. citricola may be confused with Mecynogea lemniscata.
Habitat and distribution Cyrtophora citricola is found in Asia, Africa, Australia, Costa Rica, Hispaniola, Colombia, and Southern Europe. The species is unable to survive in temperatures below -1 °C (30.2 °F). C. citricola was also discovered in Florida in 2000 and it makes its webs on canal bridges from the east end of Everglades National Park to the east coast. The spider lives in a wide range of environments, but it is most prevalent in olive orchards and undergrowth. C. citricola is also found in tropical agricultural operations.
C. citricola can be found globally, unlike its close relatives that are concentrated in specific parts of the world. C. citricola's global presence may be a problem as seen in the Americas. The spider is becoming common in agricultural and urban spaces. It is damaging farm operations. Currently, there are active efforts to remove the spider as its web is known to damage flora.
C. citricola exhibits thermoregulative behaviors. This trait is common in web-building spiders, including Nephila clavipes, N. maculata, and Frontinella communis. During the hottest portions of the day, the spider will position themselves so that as little surface area of their body is shown to the sun as possible.
Behavior
Web Cyrtophora citricola builds tent-webs that have a horizontal orb web and a network of webs above it resembling a tent. These webs can be built alone or as part of a colony. The spiders exhibit advantages living in colonies, but there is no selection towards either solitary or colonial living. Within colonies, the horizontal orb webs are solitary and maintained by individuals. Other Araneidae species have a triad complex on their posterior spinnerets which produce a gluey thread material for the webs from the piriform glands. C. citricola lacks a triad complex and is unable to make gluey thread web material so it creates a distinct non-sticky, mesh-like web.
C. citricola creates a thick silk strand barrier above the orb and a thinner barrier below the orb. The silk above the web is used to deflect insects onto the orb web below. The webs above and below the horizontal orb webs are communal and maintained by the colony. The horizontal orb web and silk are not sticky. The orb webs appear as a fine mesh curtaining, made of radii and a non-adhesive structural spiral. This structure is different than the typical Araneidae family webs, as they lack a viscid spiral. These webs are durable, and may have evolved to be created outside of citrus trees. The webs may be large enough to span entire trees and are found on a variety of tree species.
C. citricola prefers to build its webs on firm substrates rather than non-firm substrates. Webs built on firmer substrates tend to last for longer periods of time. The webs are strong enough to withstand environmental pressures, such as rain and wind. Unlike adhesive webs, which must be respun daily, non-adhesive webs are only repaired when damaged. Most of this damage occurs at the peripheries of colony webs where the costs to create orb-webs is high. The center of these colonies infrequently require repairs, saving the spider the constant investment of respinning the web.
C. citricola typically rests with all of its legs underneath its body when it is not watching over its egg sacs and uses various motions to detect prey and intrusions. The spider sits on the hub of the web. This positioning occurs during the night and day. C. citricola also participates in web jerking, an act of quickly pulling the radii with a front leg. Web jerking may occur in response to movement in the web and prey capturing. The behavior may allow the spider to accurately find objects in its web, assist in prey location, and transmit signals. In addition, the spider engages in web shaking, motions that cause sudden and rapid shaking of its webs. This shaking is created by a downward motion from the spiders' legs. C. citricola engages in web shaking to dislodge prey stuck in the upper barrier of the web. It may also shake off approaching kleptoparasites.
Prey C. citricola captures its prey in the upper section of the web. The rate of prey per capita due to web deflection is relatively low and may cause spiders to aggregate together. Spiders who live in social aggregates are more efficient at capturing prey than solitary spiders.
The process of capturing prey includes multiple steps. The first step is either biting the prey or wrapping it in silk. The second step is pulling and cutting the prey out of the web. The third step involves transporting the prey to the hub of the web by either carrying it in its jaws or rewrapping it and carrying it in silk. In the fourth step, the spider feeds on the prey in the hub of the web.
C. citricola has four attack sequences. In the first variation, the spider wraps its prey and bites it. After biting the prey, the spider removes the prey from the web, rewraps it, and transports it to the hub. The second sequence follows the steps of the first variation but skips the biting stage. The third variation starts with the spider biting its prey and wrapping its prey. Later, the prey is removed and rewrapped before being transported to the web hub. The fourth sequence involves spiders biting and pulling or cutting the prey. The prey is transported to the hub in the spider's jaws. Whether the prey is bitten, wrapped, or both is determined by the type of prey that is captured.