Araneus gemmoides

Abstract: Orb-web weaving spiders synthesize and use a variety of silks, each having different properties suited to their particular functions. Three of these silks were collected from two different species of spiders and subjected to physical/mechanical testing. The major ampullate (dragline), minor ampullate, and cocoon silks of both Nephila clavipes and Araneus gemmoides were load tested on an Instron Universal test frame to compare their physical properties. The single fibers of major, minor, and cocoon silk of Nephila appear to be more elastic than that of Araneus. Araneus silks, on the other hand, appear to be stronger, requiring a higher stress to break the fiber than that of Nephila. Through millions of years of evolution, spiders have been specializing their use of silks, to the point that many are completely dependent on the silks they produce for survival. The orb-web weaving spiders are a key example of this. They spin highly complex webs from several different types of silk, produce silk to protect their eggs, and silk to swathe their prey for storage. Orb- web spiders have at least six sets of silk-produc- ing glands (Lucas 1964; Koover 1987), each syn- thesizing a different fiber for use in a specific application. Each fiber is composed almost en- tirely of protein. METHODS

Abstract: and Summary Most orb-weaving spiders (Araneidae) possess the behavioral capacity to orient and modify their planar webs in response to wind and direct sunlight. These behaviors have generally been interpreted as tactics to avoid thermal loading of the spider or damage to the web. However, previous studies have focused primarily on diurnal araneids that sit at the hubs of their webs in exposed habitats. Here the orientations and modifications of the webs to wind and light for Araneus diadematus and Araneus gemmoides, two spiders which use retreats in less exposed habitats, are examined. Light had no effect on the web structure of A. diadematus or on its web orientation. Araneus gemmoides, however, demonstrated a significant perpendicular orientation of the plane of the web to light; a response which is probably to increase prey interception rather than control isolation. In response to wind, A. diadematus demonstrated a significant reduction in the surface area of the web, while A. gemmoides demonstrated a significant parallel orientation of the web to wind with no change in web structure. The responses of both spiders to wind resemble behaviors shown by other orb-weavers, and probably function to avoid web damage. These responses to wind and light are related to the use of a retreat, and to differences in web building behavior and habitat. Zusammenfassung 1 Die Orientierung und der Bau der Fangnetze zweier Araneus-Arten unter Wind- und Lichteinflus wurden im Windkanal untersucht. 2 Licht hatte auf Struktur und Orientierung der Netze von A. diadematus keinen Effekt. A. gemmoides zeigte jedoch im Licht eine deutliche Vertikal-Orientierung der Netzebene. Diese Spinne scheint ihr Netz nach dem Licht auszurichten; vielleicht steigert das die Beutemenge. 3 Als Reaktion auf Wind nahm bei A. diadematus die Netzflache deutlich ab. A. gemmoides hingegen orientierte das Netz parallel zum Wind, verkleinerte es aber nicht. Beide Reaktionen ahneln dem Verhalten anderer Radnetzspinnen und dienen wahrscheinlich dazu, Netzschaden zu vermeiden.

Abstract: Orb-web weaving spiders synthesize and use a variety of silks, each having different propertie s suited to their particular functions . Three of these silks were collected from two different species of spiders an d subjected to physical/mechanical testing . The major ampullate (dragline), minor ampullate, and cocoon silks o f both Nephila clavipes and Araneus gemmoides were load tested on an Instron Universal test frame to compar e their physical properties . The single fibers of major, minor, and cocoon silk of Nephila appear to be more elastic than that of Araneus . Araneus silks, on the other hand, appear to be stronger, requiring a higher stress to brea k the fiber than that of Nephila .

Abstract: INTRODUCTION Spiders are unique in the animal world due to the use of silk throughout their life span and a nearly total dependence on silk for their evolutionary success (Lucas, 1964; Vollrath, 1992). There were periods of fairly intense study of spider silk prior to World War II and in the late 1950s. However, progress was relatively meager, especially when compared with research on silkworm silk. Beginning in the 1970s, studies carried out in the laboratories of Work, Gosline, and Tillinghast reinvigorated interest in spider silk, with several papers describing their physical, mechanical, and chemical properties. These papers set the stage for the current advances in our understanding of these fibers. BIOLOGICAL ASPECTS OF SPIDER SILK PRODUCTION Typical spider webs are constructed from several different silks, each of which is produced in a separate gland. Non-orb web-weaving spiders produce fewer silks and use them differently in many cases. The non-orb weavers constitute the majority of spiders and include those species that do not make the usual orb-shaped web. The various silks produced by the orb web-weaving spiders, the glands that produce them, and the uses of the spiders for each silk are listed in Table 7.1. Although each of the silk glands has its own distinctive shape and size, they are all functionally organized in a similar pattern. The majority of the gland serves as a reservoir of soluble silk protein that is synthesized in specialized cells at the distal end of the gland.