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Nephila pilipes

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Nephila pilipes

Nephila pilipes (northern golden orb weaver or giant golden orb weaver) is a species of golden orb-web spider. It resides all over countries in East and Southeast Asia as well as Oceania. It is commonly found in primary and secondary forests and gardens. Adult females are very large, with a body length of 25 to 50 mm (1 to 2 inches). Males are dwarfs, measuring only 4 to 6 mm (about 0.2 inch). It is the second largest of the orb-weaving spiders apart from the recently discovered Nephila komaci. The first, second, and fourth pairs of legs of juvenile females have dense hairy brushes, but these brushes disappear as the spider matures.

The N. pilipes golden web is vertical with a fine irregular mesh. It is not symmetrical, with the hub usually nearer the top. Rather than egg sacs being hung in the web, a pit is dug which is then covered with plant debris or soil.

N. pilipes display female gigantism and male dwarfism (see Sexual dimorphism section). In terrestrial animals, N. pilipes have the most size differences between males and females. This can be explained by the evolutionary selection for females with better fecundity. Female N. pilipes have huge parental investments to their progenies, including egg production and web construction (see Parental care section).

Females typically have a body size of 30–50 mm. The cephalothorax is about 15 mm long, 10 mm wide. The abdomen is about 30 mm long, 15 mm wide, mostly dark yellow-brown color with yellow stripes. The tergum is generally black or brown, covered with dense hairs. Both rows of eyes bulge towards the rear. The plastron is mostly black and brown. The legs span very long, and they are black and yellow. There are no apparent hairs on all legs. It has been reported that this sharp contrast between yellow and black color can increase foraging success towards visually-oriented prey.

Males’ body size is typically 5 mm to 6.5 mm. The cephalothorax is about 2.5 mm long, 2 mm wide. The abdomen is about 4 mm long, 1.5 mm wide. Front eyes are larger than rear eyes. Males have light brown legs, with some hairs. The carapace is yellow with very few hairs.

N. pilipes has a few different features which make it easy to distinguish from similar species. Unlike Trichonephila clavata, N. pilipes has a horn-like bulge on its tergum. Additionally, it has a pair of yellow stripes at its back of the abdomen unlike Nephilia laurinae.

N. pilipes display sexual dimorphism, the presence of distinct difference between the males and females of a species. In N. pilipes, female spiders are much larger than their male counterparts, and males can be 4–10 times smaller than the females.

The fecundity selection in Nephila pilipes causes females to continuously molt even after maturation. Although most spiders shed off all their exoskeleton during molting, Nephila pilipes do not shed off genitals during molting, so they can keep collecting sperms. The number of mating will affect the post mature molting. Also, females are more likely to exhibit post-maturity molting if copulations are short in time. After mating with one male, female Nephila pilipes will accumulate sperms until they collected enough. This can be explained by fecundity selection. In order to maximize the number of progenies, females have the incentive to continue their body growth after sexual maturation until they have a number of fertilized eggs above certain threshold. Females will use chemical signaling to attract more males to serve them after molting. This claim is supported by a study on N. pilipes' relative Trichonephila clavata, in which males highly prefer females that molt recently.

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