author(s)
Irfan Zia Qureshi and Amjad Altaf

abstract
Spiders are the most diverse group of invertebrates that inhabit almost all terrestrial environments. Among colonial spiders, the sheet web spider (Stegodyphus sarasinorum) Karch, 1892, weaves sheet webs for prey capture. We studied and compared different morphological structures of sheet webs through scanning electron microscopy. Round, bilateral, bifurcated, cribellate fibers, network of extended silk fibers with ribbon clumps, zig zag fibers and silk droplet enwrapped with tiny silk threads were frequently observed in the sheet webs. Comparison of silk fiber samples from colonial spiders was also made with the orb weaving spiders (Eriophora transmirana). Mean diameter of silk fibers in sheet weaving spiders was 1.215 µm, while mean diameter of silk fibers of orb weaving was 3.21 µm showing significant difference (p<0.05). Distinctive single strand rounded, and double strand rounded, loop shaped structures were observed in sheet webs of sheet weaving spiders. The tiny threads which were extensively present in the scaffold of sheet web. These tiny threads were exclusively present in the sheet weaving spiders. It is predicted that in future we would be able to understand the spinning mechanism of sheet fibers by the cribellate gland, the smallest gland in Stegodyphus sarasinorum, to investigate the mechanical properties of these fibers. An understanding of the mechanical properties of these fibers, especially small wool like fibers may lead to the synthesis of nano scale fibers.