Description
''T. spectabilis'' undergoes a unique color transformation from yellow to white. The color change helps them not only hide from predators, but stalk prey in similarly colored daisies as well. This transformation allows them to switch between appearing conspicuous and cryptic to their prey. The colorful bodies allow spiders to reflectPhylogeny
Closely related species
Australian crab spiders are very similar to other crab spiders across the world, such as the European, Alaskan, or Canadian crab spider. A similarity in these spiders is that rather than building webs, they hide from their prey and ambush them with their forelimbs. Crab spiders are in the familyHabitat and distribution
Habitat
The Australian crab spiders choose habitats that increase their chances of catching prey. Since this involves creating contrast between itself and the flower, it will pick flower colors and flower positions that maximize the contrast. Due to the importance of contrast with flowers, these spiders cannot simply choose habitats with large numbers of its prey. Instead, they must think about both flower type and prey number while choosing habitats in a way that maximizes capture. ''T. spectabilis'' is mostly attracted to staying in flowers that are newer, and is drawn to them through olfactory cues. It is most commonly found in tropical or subtropical areas, but some also prefer white clothing lines.Geographic distribution
They are spread throughout Australia, but are primarily located in Eastern Australia. It is mainly a suburban spider. In Brisbane, they are normally found in backyards, bushes, and gardens.Diet
These spiders are a predatory species, and they feed mainly on insects. They mainly eat live or recently killed insects. Some examples of these insects areWebs
Australian crab spiders do not build webs, as they capture their prey through ambush and hiding rather than web capture. They will use fallen leaves or live foliage to hide their bodies, which are easy to camouflage due to its color in order to ambush their prey. They can wait up to periods of 2 hours hidden under foliage in order to strike their prey. However, they do still have the ability to make silk, and typically use it to build retreats. During the day, they rest in these retreats that are composed of silk and leaves. At night, they come out of their retreats to wait on flowers and ambush their prey.Behavior
Prey capture
Cues
This is a spider that does not capture prey through webs, but instead sits on flowers and ambushes pollinators as they arrive to the flower. They use cues from their prey and from the flowers to pick their habitat. Although many spiders use camouflage to hide from spiders before eventually attacking them, the Australian crab spider is actually not cryptic to its prey as it hides. In fact, honeybees can visually determine the difference between the spiders and the flowers in which they are waiting. The mechanism of deceit for Australian crab spiders involves influencing and exploiting signal communication between pollinators and plants. Insects choose plants that have larger flowers, available nectar, a specific odor, a certain color, or a certain symmetrical pattern on the flower. Honeybees specifically are attracted to flowers with certain odors (implying high nectar reward), colors, and symmetrical patterns. The Australian crab spider uses the same combination of visual and olfactory cues that attracts the bees to arrive at the same flower as the bees.Symmetry affinity
The honeybee's affinity for symmetry leads it to pollinate flowers with symmetrical patterns. Bees and Australian crab spiders are both drawn to symmetry, and this leads both the predator and prey to come together at the same flowers. Coevolution of bees with the Australian crab spider has resulted in the spiders being attracted to the same cues as the bees. It has also resulted in the bees developing anti-predatory behavior. Despite the heightened risk of going to the same flowers as the Australian crab spiders, they continue to do it because those flowers present the highest potential reward in nectar and freshness for the bees. Honeybees show a strong preference for radial symmetry over bilateral symmetry while crab spiders do not discriminate. The white crab spider's preference for symmetry, along with olfactory cues, draws it to hide among flowers and ambush honeybees as they arrive. The olfactory cues tell the honeybees which flowers hold the biggest rewards for them, and these spiders have evolved to be attracted to that same scent because the bees are the spiders' reward.UV reflectance
The spiders are able to actively influence honeybees to come to the flower that they are positioned on. When the Australian crab spider is in its white body state, it is able to reflect UV light. This reflected UV light causes activation in the UV photoreceptors of the bees, and increases the UV receptor contrast and the contrast between the spiders and the flowers. The bees are attracted to this contrast, and subsequently go to the flowers at which they are ambushed by the spiders. There is temporal and individual variation in UV reflectance between Australian Crab spiders. This variation is most frequently in the range of 300 nm to 400 nm. Temporal variation can be seen in differences in UV-reflectance between different years. In 2008, ''Thomisus spectabilis'' were more UV-reflective and created larger color contrasts with flowers than in 2009. This temporal variation is correlated with the spiders adopting strategies switching between low and high conspicuousness. This is necessitated by a combination of ''Thomisus spectabilis prey and predator behavior and the balance of attracting prey while maintaining safety from predators. The most common predators of the spider are wasps and birds, and both of these animals are able to perceive UV-light. Thus, the Australian Crab Spider is much more likely to be harmed in a white UV-bright reflective patterns than a white UV-dull reflective pattern.Gawryszewski, Felipe M., Ana L. Llandres, and Marie E. Herberstein. "Temporal and individual variation in Australian crab spider UV-colouration: the link between colour, condition and background." ''Interacciones entre arañas cangrejo y polinizadores: estrategias de caza de las arañas cangrejo y estrategias antidepredatorias de los polinizadores'': 57. Individual UV-reflectance variation is not necessarily due to the amount of prey they have already consumed, as their adjustment is based on prey availability and environment rather than satiation. It is also not due to the body size or shape of the spiders. Rather, it has the strongest relationship with predator presence. In the absence of predators, UV-Reflectance will always increase because it always makes them more likely to attract prey. This is in stark contrast to other spider species, such as ''Mechanisms of color polyphenism
There is variation in the hypodermal layer of spiders with different body color phenotypes. For yellow body spiders, the hypodermis is composed of granules, filled with electrons, and does not contain crystals. White non-UV spiders have their hypodermal layer filled with random patterns of crystals. White UV spiders have granules and little to no crystals in their hypodermis. The most significant aspect of the variation is the lack of granules for white non-UV spiders. The crystals of the hypodermis fluoresce under UV light. The structure of the guanocyte layer does not show distinct patterns for different color phenotypes. ''Thomisus spectabilis'' differs from other crab spiders in that its UV reflectance, hue, saturation, and brightness profiles are very different between its three phenotypes. There is a 56 nm shift in hue from the white UV spiders to the white non-UV spiders, and a .05 difference in saturation between white UV and white non-UV spiders. Brightness of white UV-Spiders was 7.9% higher than for white non-UV spiders. The cuticles of white UV and white non-UV spiders reflect UV light very similarly across the spectrum, but yellow non-UV spiders transmit less light throughout the spectrum, specifically in the 380-500 nm region. Similarly, the guanocytes of white non-UV and white UV spiders reflect UV light similarly, but yellow non-UV spiders reflected less throughout the spectrums as well. Guanocytes across all phenotypes sharply dropped off reflection at wavelengths under 330 nm.Positioning
Another crucial aspect of prey capture for the Australian crab spider lies in its exact positioning on the flower itself. Honeybees are attracted to flowers partially based on the amount of rewards they have, and this is determined from looking at the center of the flower. To ensure they don't come in the way of that, it is vital for the spider to position itself on the lingulate floret of the flower away from the center. This allows them to create the color contrast in the bee's vision that draws them to the spider-laden flowers.Effect of spider size and movement on prey behavior
''Thomisus spectabilis'' with larger body sizes are better able to capture prey. Honeybees are more likely to land on flowers that have larger spiders than smaller spiders. Thus, larger Australian crab spiders do not have to use their UV-reflective property as much as smaller spiders to attract bees. For smaller spiders, using UV-reflectance results in less hunting success than larger spiders using UV-reflectance; spider size is a larger factor than UV-reflectance for predicting bee attraction and hunting success. Further, levels of UV-reflectance increase for larger spiders suggesting coevolution of size and UV-reflectance traits.Llandres AL, Rodrı´guez-Girone´s MA (2011) Spider Movement, UV Reflectance and Size, but Not Spider Crypsis, Affect the Response of Honeybees to Australian Crab Spiders. PLoS ONE 6(2): e17136. doi:10.1371/journal.pone.0017136 Movement of ''Thomisus spectabilis'' has large impacts on the behavior of honeybees. If they move before honeybees approach, the bees are much more likely to stay away from the flower. This effect is more pronounced when the spiders are waiting below the inflorescence of the flower rather than above it. Below the inflorescence, the spiders remaining still makes them 70% more likely to attract a spider to land, but above the inflorescence they are 50% more likely to attract a spider to land by remaining still. Movement of crab spiders alerts bees to their presence. This forces the bees to make a decision weighing the risk of the spiders and the reward of the nectar. These decisions are also influenced by the susceptibility of the bee. Highly susceptible bees mostly visit safe flowers, even if the resources are poor in those areas. Other bees often must choose riskier patches of flowers, because those flowers often contain the highest amount of nectar. Since the flowers with hiding spiders often become damaged due to the ambush of the bees, they actually have evolved to increase nectar production so that they can continue to attract bees despite the threat of predation. Honeybees are adept at finding the best flower patches to maximize nectar reward and minimize predation risk due to their impressive communication system. Bees are able to recruit bee mates to flower locations that they have scouted as high nectar locations, and they are also able to tell each other when there is a patch with hiding spiders.Female/male interactions
''T. spectabilis'' is sexually dimorphic, where the female spider is larger and stronger than the male spider. Thus, it is the female spider that lies in flowers waiting for pollinators to ambush and capture. The male spider spends the majority of its time searching for females to mate with, and they eat very little overall. The females have evolved to have higher reflectance of light on their abdomen than male spiders; this reflectance is vital to helping them deceive and capture pollinators. Females are also responsible for building the egg-sacs. They build them on curved leaves, and are responsible for guarding the eggs and the offspring.Coevolution of prey and predator
The Australian crab spider eats a variety of bees, but the two main varieties areBite
''T. specabilis'' typically bites more frequently than most spiders. The bites are venomous, and can have mild but significant effects on humans. These effects range from localized pain, redness, dizziness, headaches, nausea, and swelling, but the symptoms generally subside in 1–2 hours after onset.See also
*References
{{Taxonbar, from=Q3395005 Thomisidae Spiders of Australia Spiders of Asia Spiders described in 1859