Some Cyrtophora spp. (Araneae: Araneidae) build silk stabilimenta

Abstract

Spiders in the genus Cyrtophora Simon, 1864 often incorporate debris and egg sacs in their webs. Based on a survey of online digital imagery, I report here that at least three species in this genus also include silk decorations: C. cylindroides (Walckenaer 1841), C. ikomosanensis (Bösenberg & Strand 1906), and C. moluccensis (Doleschall 1857). These species lay single to multiple zigzagging silk strips in an arcuate, looping, or spiral pattern often centred about the web’s hub. However, small juveniles and males installed scattered floc-like silk in the barrier strands below the web. The most commonly observed decorator, C. moluccensis, displayed the devices in only 13.9% of observed webs (n = 465), lower than most other silk-decorating spiders. The discovery of novel spider behaviour and web structure is considerably aided by online databases of natural-history observations.