Studies On Ecology Of Spiderling, Web's Structure And Dragline Mechanical Properties Of Argiope Amoena

Other researches have showed that cooperating with others in foraging is the mechanism of subsocial spiders living together, and contesting for food is the main cause of dispersal. In this study, we put the light on Argiope amoena, which is solitary spider, and conduct the following researches: 1) inspecting the cases of the spiderlings including ones that come through social phase and not, under room temperature(26±0.5℃) and lower temperature(16±0.5℃); 2) conducting the research on the ability of tolerating adversity of the spiderlings under room temperature(26±0.5℃) and controlled temperature(D: 10±0.5℃, L:20±0.5℃; L/D: 13/11); 3) inspecting the mode of spiderlings dispersal, and the mode of spiderlings using limit space. The results are: 1) some spiderlings can weave webs after they incubated from egg sac; 2) the ability of tolerating adversity of spiderlings under controlled temperature is better than the ones of spiderlings under room temperature, and the time of the spiderlings begin death and the median lethal are longer than the time of dispersal; 3) spiderlings usually dispersing by the way of collective aviation. Then we can get these conclusions: 1) some spiderlings have the ability of weaving web after they incubated from egg sac; 2) spiderlings can survive even if they are not feed during the social phase(actually spiders that we feed in laboratory did not eat anything during this phase; 3) the way of spiderlings dispersal may make them minish threaten from predators and energy consuming. We speculate that minimizing the cost of dispersal (including resisting predators and energy consuming) and maintaining height level of population survival rate (getting effective depending predators by living together with the spiderlings that can not weave webs) may be the main cause of spiderlings living together. Webs are used by spiders to capture prey, and their structure and mechanical properties can affect the efficiency of prey capture and foraging investment. In this study, we examined webs from different sized spiders. Results indicate that among spiders under 200 mg, there exists a positive relation between the spider's mass and the capture thread length, capture spiral space, and capture area. This relationship was not seen in spiders larger than 200 mg. Furthermore, there was a negative relationship between the radius of the web and the spider's mass. In spiders under 200 mg, there was a negative relationship between spider mass and the ratio of the upper capture thread length to lower the capture thread length. These results are consistent with our hypothesis that changes in web structure reflect the foraging investments and strategies of different sized spiders. There is a decoration on the webs of Argiope amoena, called stabilimentum. There are at least eight hypothesis about their function have been proposed, including attracting prey, defending against predator and protecting web. These functions are not mutually exclusive and silk stabilimenta may serve more than one function. But which is the primary one? We conduct three experiments: weight experiment, space experiment and starvation experiment, to determine it. The result are these: 1) the stabilimentum was only found among spiders above a certain weight (in our study, the smallest spider having a stabilimentum was 22.7 mg) and total stabilimentum area was related to the spider's mass; 2) stabilimenta of the webs weaved by the spiders in the small case are more weight than ones of spiders in large case, though capture length and capture area are smaller than that of spiders in large case; 3) capture length, capture area and weight of stabilimentum are all decrease after 30-day starvation, but the weight of stabilimentum decrease more badly than the others; and the weight of stabilimenta of the three consecutive webs vary significantly while capture length and capture area not. All the results may indicates that stabilimentum is the decoration build to attract prey.Dragline has many biological functions, such as the tool of escaping and building webs, its mechanical property may be influenced by some inner and outer factors. Therefore, we survey mechanical property of the draglines from the spiders of different weights, different foods, and well-feed and starved, and we also compare the mechanical property of filament from same silk. We find mechanical property of spiders from different levels, same level and same individual vary significantly, and it makes we difficult to determine the influence of the conditions (different weights, different foods, and well-feed and starved). The diameter of silks increase after the weight of spiders, and it will have better mechanical property, and available when escape. Compared to the mechanical property of the silks from the spiders did not undergone starved, the breaking strain and breaking energy of the silks from the starved spiders are decrease badly, but there are no difference found near yield point, it may be a strategy spider taken when intake energy is limit, since elasticity is more important than plasticity.