Speaker: Javier Castillo
Candidate for a Bachelor of Science Degree in Biology
Time: 5:45 PM
Place: Trustee Hall 116
Supervisor: Allan Hook
Title: Insect attraction to the webs of the common garden spider, Argiope aurantia

Abstract: Current research regarding spider webs and their morphology has concluded that derived aerial web-weaving spiders (superfamily Araneoidea) produce catching silks that selectively reflect ultraviolet light (350-400 nm). This is a characteristic that is found in the primitive superfamily (Deinopoidea), but has been modified by the araneids at the molecular level to make prey capture by spider webs more efficient. The two main factors that affect prey capture by spider webs are the ability of the web to absorb kinetic energy of prey impact (web density) and the ability of the webs to intercept prey (web visibility, including UV-reflectance since insects are able to see UV light). Experimental and field tests have shown that there is a correlation between the three and all are a function of the amount of biomass the spiders will consume per energy input in capturing prey. In addition, the common garden spider, Argiope aurantia, has adapted a unique foraging strategy in which both UV-reflecting and non-UV-reflecting silks are spun on the same web. Argiope decorate their webs with UV-reflecting silk zig-zags known as stabilimentum, while the rest of the web reflects little or no UV light. The function of UV-reflecting stabilimentum is to attract insects using the same strategy that UV-reflecting designs on flowers attract insects.