internal temperatures at an optimal level. As ambient temperatures increase, the spiders position themselves so the abdomen shades the cephalothorax from the sun. Spiders may also hang from their hind legs as a result of the heat due to a loss of hydrostatic pressure. Conversely, as temperatures cool down, the spiders position themselves perpendicular to the sun to retain as much heat energy as possible. When ambient temperatures reach extreme highs (above 40 °C), they may leave their webs and seek shade in the surrounding environment. Predation and parasitism Predation of Nephila species is relatively uncommon; when it does occur, the main group affected are the juvenile individuals. The major predators are birds, but wasps and damselflies also prey upon smaller juveniles. Nephila species are frequently parasitized by Argyrodes, a genus of very small black-and-silver spiders that are kleptoparasitic. As many as a few dozen may infest a single Nephila web to feed from the host spider's captured prey. The frequent rebuilding or abandoning of webs by Nephila may be a tactic for controlling Argyrodes. Spiny orb-weaver spiders of the genus Gasteracantha also inhabit the webs of Nephila as kleptoparasites. Egg sacs generally remain free from both predation and parasitism, often due to the close proximity of the mother and how well it is hidden. Life cycle Spiderlings Nephila spiderlings leave the egg sac as a result of environmental cues, often warmer and wetter conditions in spring. They then live on a communal web, eating dead siblings and web debris for around a week before dispersing to make individual webs. Young spiders do not generally build yellow-colored silk, and the young themselves can be easily mistaken for young orchard spiders (Leucauge) in general color and shape (both genera sport silver stripes or patches on their abdomens, described in some references as a form of heat control). The best distinction between Leucauge and Nephila juveniles is web structure: Leucauge species tend to build horizontal orbs that form a perfect circle, whereas Nephila species build vertical, elliptical orbs that are incomplete (missing the portion of the orb over the hub, the center where the spider sits). The latter seem to prefer more open habitat such as second-growth scrub or forest edges. Fences or building overhangs often do just as nicely. Molting and growth Once they are juvenile, Nephila spiders inhabit their individual webs, then begin their growth by the molting process. The