Cyrtophora citricola

Cyrtophora citricola, also known as the tropical tent-web spider, is an araneid spider that can be found in Asia, Africa, Australia, Costa Rica, Hispaniola, Colombia, and the warmer parts of Europe. In 2000, it was also discovered in Florida.

Although it is in the family commonly called Orb Web Spiders, this spider does not build orb webs and their webs are considered atypical and has been described as having a mesh-like, horizontal appearance. The difference in their web silk can be explained by unique physiological changes to their spinning apparatuses. The spiders have developed unique prey- capturing techniques which utilize their atypical webs. These spiders can be social, and their webs are often built in large matrices next to one another.

These spiders are most active at night, preferring to carry out only necessary tasks during the day. During the day, they primarily remain idle and try to stay out of sight from predators. At night, they conduct most of their foraging and prey capture.^[1] They may also have to ward off other spiders in the colony that may try and claims their orb-webs.^[2]

C. citricola's color may vary greatly; whereas many sport a black and white pattern, others are brown, males sometimes appear black. Body length in females normally reaches 10 mm, with males only 3 mm long.

Cyrtophora citricola's exhibit high rates of sexual cannibalism, in that they eat their male partners after mating. The females' egg sacs are flattened and elliptical shaped and up to ten egg sacs can be produced by a female.

Cyrtophora citricola spiders are a medium brown color, though may display darker brown spots on the abdomen. In Florida specifically, male spiders are black and females vary in their coloring and can camouflage in their webs. Cyrtophora citricola male and female spiders exhibit sexual dimorphism, with the male spiders (3mm in length) being significantly smaller than the female spiders (10mm in length). Uniquely, Cyrtophora citricola exhibit a horizontal bifurcation at the posterior abdomen.^[3] It also is distinguishable from its other relatives by its two pairs of dorsal tubercles and its posterior tubercles pair.^[4] Larger spiders are typically dominant over smaller spiders.^[5] The females have been found to exhibit white hairs. The spiders have seven denticles. The opisthosoma has two dorsal pairs of protuberances and two posterior lobes.^[6]

Like others in the Cyrtophora family, their 2nd, 3rd, and 4th legs have a shorter combined patella and tibia length than femurs within the same legs. Additionally, they share the same bent-back eye pattern: a typical family defining trait.^[7] They differ from the Manogea genus of orb-web spiders due to their broader cephalic structures.^[4]

They are most active from the middle of summer to the beginning of fall. Adults are seen and mate between June and September.^[4]

These spiders are unique compared to their close relatives due to their widespread habitation.^[8] Most of their close relatives are concentrated in specific parts of the world. However, their introduction to the Americas has caused many problems. They are now becoming increasingly common in agricultural and urban spaces, damaging farm operations. Currently, there are active efforts to remove these spiders as their webs are known to damage flora.^[7]

Cyrtophora citricola can be found in Asia, Africa, Australia, Costa Rica, Hispaniola, Colombia, and the warmer parts of Europe. These spiders live in a wide range of environments, from plants and trees to urban areas. They have also been documented in tropical agricultural operations.^[1] It was also discovered in Florida in 2000, where it makes its webs on canal bridges from east end of Everglades National Park to the east coast of Florida. Studies have suggested that Cyrtophora citricola cannot survive at temperatures below 1 degree Celsius.^[3]

In Turkey, these spiders usually appear brown with grey hair. They have been most documented in olive orchards and undergrowth.^[4]

Cyrtophora citricola exhibits territorial behavior over their orb-webs. However, tent-webs are seen as communal, and no aggressive behavior has been documented between spiders that travel across these webs. At night there are conflicts between orbless spiders and those that possess orbs. These fights occur due to competition for better feeding locations. Invading spiders may come from the colony's periphery, where costs to build webs may be high due to more frequent repair and diminished prey capture. The conflict ensues typically when an orbless intruder approaches the web and vibrates it. This action is a sign of an attack which solicits the same response from the defending spider. The vibrations between the attacker and the defender continue for up to a few minutes. However, the invader rarely captures the web under contestation and eventually retreats.^[2]

Upon reaching adulthood, the male spiders will look for females, and then die shortly after mating has occurred.^[12] These spiders exhibit sexual cannibalism at high rates. The female spiders often will eat the male spiders directly after mating with them.^[13] This sexual cannibalism encourages males to be very choosy in who they pick as their female mate. Studies suggest that females are not choosy in their male mates, but that males preferred to mate with younger, more well- fed females.^[14] Additionally, males give preference to mating with virgin females over females that have already copulated. ^[14]

When they mate, the female initiates the process. Females traditionally approach the male until they are about 1cm from the male. At this point, the male advances quickly towards the female and tries to insert his pedipalp. If successful, copulation begins and lasts for a few seconds.^[14]

The male Cyrtophora citricola does not somersault into the female’s chelicerae. The female bends her cephalothorax and orients herself to attack the male’s abdomen while the pedipalp is in the female. The male is then eaten and the pedipalp detaches from the female.^[14]

Cyrtophora citricola may exhibit aggregate social interactions with one another and live cooperatively in groups. The spiders make their own individual webs, but these individuals webs are interconnected in a larger network of webs with neighboring spiders, creating a massive web matrix. They generally coexist peacefully, but if another nearby spider tries to take their prey, they may exhibit aggressive behaviors.^[3] This colony living was initially thought to have evolved because of the foraging benefits of group living for the spiders. However, studies suggest that when the spiders are under food- stress, they do not prefer to live in groups, suggesting that there must be some other evolutionary reason that group living evolved in this species.^[5]

Some Cyrtophora citricola live solitarily. When compared to those living in colonies, the solitary spiders have larger webs, produce more eggs, and have more kleptoparasites.^[1]

Argyrodes argyrodes, another species of spider, has been found to steal both the Cyrtophora citricola's prey and eggs.^[3] In addition, Holocnemus pluchei have been found to build their webs off of Cyrtophora citricola's webs. In addition, Holocnemus pluchei have exhibited aggressive behavior towards Cyrtophora citricola. They have been observed attacking and eating Cyrtophora citricola juveniles.^[1] The spider will drop to the ground if attacked, in an attempt to camouflage.^[12]

Argyrodes gibbosus often acts as a kleptoparasite on Cyrtophora citricola, stealing prey that the Cyrtophora citricola caught.^[1] They are known to switch strategies depending on where the host is located. The prey is stolen when the host is in the web. They have been observed waiting for the Cyrtophora citricola to go foraging before consuming their eggs.^[16]

Pediobius pyrgo are a type of wasp that lays their eggs in Cyrtophora citricola egg sacs. They are present in the Iberian Peninsula and in the Canary Islands.^[17] Philolema palanichamyi are a type of wasp that lays their eggs in Cyrtophora citricola egg sacs. They affect these spiders primarily in the Canary Islands and can affect around 40% of egg sacs. Wasp larvae feed on the spider’s eggs and each larva will devour significant portions of the egg sacs. The incubation takes approximately seven weeks. These often cause a large portion of parasitized spider egg-sacs to die. Parasitization approximately decreases emerging spiderlings by 60%.^[17]

If Cyrtophora citricola is disturbed by a predator, it may pull all of its legs inwards towards its abdomen.^[10]

They can change their abdomen's color to blend in with the environment.^[2] The coloring of the female Floridian spiders allows them to appear as brown, dead leaves when sitting in their webs, preventing potential predators from spotting them.^[3]

Sources

• Álvares, É.S.S. & De Maria, M. (2004). First record of Cyrtophora citricola (Forskål) in Brazil (Araneae, Araneidae). Revista Brasileira de Zoologia 21(1):155-156 PDF doi :10.1590/S0101-81752004000100026
• Edwards, G.B. (2006): Cyrtophora citricola (Araneae: Araneidae), a Colonial Tentweb Orbweaver Established in Florida. Entomology Circular 411:. PDF
• Platnick, Norman I. (2009): The world spider catalog, version 10.0. American Museum of Natural History.

• Pictures of C. citricola
• Pictures and information on C. citricola from Portugal
• Cyrtophora citricola ^{[permanent dead link ]} on the UF / IFAS Featured Creatures website.