Spider’s weight

The mechanical strength of draglines as a lifeline for spiders may be related to the spider s weight, but no studies have yet been reported regarding the relationship. Thus, the safety coefficient for the lifeline should be considered for the... 

Fig. 4.51 ES at a stretching velocity of 3.3 X 10 m/s for a M clavata spider s dragline is plotted against the spider s weight (W). The spider s weight is more than 50 mg.

Figure 4.52 shows the relationship of the elastic limit strength ES v. spider s weight W for spiders weighing less than 50 mg. The ES increased linearly with increasing W. Experimentally, we may express ES as... 

Fig. 4.53 Spider s weight (W) dependence of safety coefficient (5C) for the draglines secreted from N. clavata spiders. The SC is defined as the ratio of the elastic limit strength of the dragline to the spider s weight. The standard error in the observed values of elastic limit strength and cross section area was 5%.

Here, in order to consider the draglines from the structural point of view, it is important to estimate the value (S/W) of the cross section area S of the dragline per spider s weight W. 

Figures 4.54(a) and (b) show a cross section (S) of a dragline plotted against the spider s weight W for spiders of less than 50 mg and more than 50 mg. S increases with increasing W. We can observe a break at about 50 mg. The slope...

A drastic change in the safety coefficient from 3 to 2 was observed at about 50 mg of N. clavata spiders in summer when divergence of sex and rapid increase in the female spider s weight after the final ecdysis occurred. The spider s weight of about 50 mg corresponds to the weight at the stage when spiders grow from immature to mature in summer. 

The cebid monkeys vary in size from the squirrel monkey (S. sciureus) with a body length of 10 in (25 cm) plus a 15 in (38 cm) tail, and a weight of about 1.5 lbs (0.68 kg), to the woolly spider monkey, or muriqui, which has a body length of 18 in (46 cm), plus a 30 in (75 cm) tail, and weighs about 35 lb (17.5 kg). The males and females of most species of cebid monkeys are approximately the same size, but the two sexes often have different colorings, a phenomenon known as sexual dimorphism. 

The neuroactive agents from widow spiders are called a-latrotoxins they appear to form trans-membrane channels and usually have high molecular weights ( 130,000). They cause massive release of neurotransmitters as they stimulate fusion of the S maptic vesicles (which contain neurotransmitters) with the pre-synaptic membrane. The Australian red back spider often bites people who are in bed or asleep and the venom has a long-term effect, with patients recovering partially and then collapsing with further pain, numbness of an affected limb and even paralysis, still being affected two months later. Studies have shown that... 

Fig. 4.41 Force-elongation curves of the radial and spiral threads prepared from an Argiope bruennuichii spider with a weight of 0.949 g. Stretching velocity 3.3 X10 m/s.

Fig. 4.49 Stress-strain curve of a dragline secreted from a N. clavata spider with a weight of 471 mg, at a stretching velocity of 3.3X10" m/s. Elastic limit stress (ELS) and elastic limit strain (ELN) are defined, respectively, as the stress and the strain at which the stress-strain curve shifts from the linear to the nonlinear region.

The relationship between BS and W was examined for N. clavata spider draglines at a stretching velocity of 3.3 x 10 m/s. The breaking strength also increased linearly with increasing weight, with the slope determined to be near 6. The relationship between the BS and W was found to be expressed by the following empirical equation ... 

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