Complete Guide To The Spiny-Backed Orb Weaver Spider

Spiny-Backed Orb Weaver Spider Notes

• Spiny-Backed Orb Weaver Spiders live only in the coastal plain of North Carolina.
• Despite their small size, Spiny-Backed Orb Weaver Spiders build large orb webs in shrubs and low tree branches.
  • Male Spiny-Backed Orb Weavers sometimes hang from the females’ webs on single silk strands (Bradley 2012) but are otherwise hard to spot in the wild.
  • Female spiders are more obvious and easier to find as they are larger, colorful, and hang upside down in the middle of the large webs during the day.
• The webs themselves are conspicuous even from a distance, which helps humans avoid walking face-first into their webs.
  • Webs can span up to nearly 20 inches (50 cm).
  • Webs are spun of thick silk that shines in certain angles of sunlight.
  • The spiders weave the spiral strands very close together, which makes them easy to see.
• The spines on female Spiny-Backed Orb Weaver Spiders may have evolved as protection against predators, and the color morphs may have evolved to both warn predators away and attract prey.
  • Different prey species may be attracted to different color morphs, as the spiders’ colors may mimic flowers.
  • Alternatively, some spider predators may notice certain color morphs more than others.
  • A study completed by Nathalia G. Ximenes and Felipe M. Gawryszewski showed that:
    • Yellow morphs appear to attract both predators and prey alike.
    • Red morphs attract butterflies as prey and birds as predators but appear inconspicuous to flies as prey and spider-eating wasps as predators (Ximenes and Gawryszewski 2019, https://doi.org/10.1093/cz/zoy069).
  • On the other hand, a study by Fabian C. Salgado-Roa and co-authors showed no significant difference in prey capture success between the different female Spiny-Backed Orb Weaver spider color morphs. Instead, the brightness of the light in which the spiders built their webs impacted prey capture rates; webs built in dim light caught approximately 70% more prey than webs built in brighter light (Salgado-Roa et al. 2023, https://doi.org/10.1007/s10682-023-10244-6).