Spatial Distribution of Spider Webs on Street Lights and the Deterrent Effect of Space Filling on Web Construction

It is well established that a wide range of spider species spin webs on artificial light sources such as street lights. The presence of webs on lighting equipment not only detracts from the aesthetics but can also reduce their function in terms of illumination. To address these problems, we compared the distribution and number of spider webs on conventional street lights and novel spider-proof street lights in which the space below the lamp is filled with an enclosure. During the study period, 49 webs were constructed on the conventional lights and only 19 on the spider-proof lights. In addition, more webs were spun on the light-emitting side of the conventional street lights, whereas on the spider-proof street lights, webs were observed only between the pillar and the light. To further investigate whether the removal of a web-forming space suppresses web construction, we compared the frequency of webs after filling the space on the light-emitting side of the conventional lights with differing amounts of a transparent acrylic (0%, 50%, 75%, and 100%). We found that of the 37 webs observed, 31 were constructed on conventional street lights with less than 75% filling, which is significantly higher than that on lights with 100% filling and on the spider-proof street lights. These findings indicate that spiders tend to construct webs on the light-emitting side of street lights, and that filling this space may contribute to reducing the construction of webs.