Opell (30 risultati)

Differences in web structure and cephalothorax features suggest that Hyptiotes cavatus should exert more force while monitoring its vertical triangle-web than Uloborus glomosus exerts while hanging beneath the hub of its horizontal orb-web. When this hypothesis was tested by measuring the force that instars of each species exert…

In the Uloboridae, web reduction is accompanied by changes in opisthosomal shape, leg length, and web-monitoring tactics. These morphological changes make reduced-web spiders more cryptic and alter their leg leverage and centers of mass. When compared with the orb-weaver Uloborus glomosus, the irregular, reduced-web spider, Miag…

Uloborids that spin reduced webs more actively monitor them than those that construct orb webs. Hyptiotes use both their first and fourth legs to tense their triangle-webs, whereas Miagrammopes rely principally on their first legs to monitor and jerk the threads of their irregular webs. The respiratory systems of these spiders i…

In uloborid spiders, eye loss is accompanied by increased visual angles, optical material investment, and potential visual acuity of the retained eyes. Relative to carapace volume, the six-eyed Hyptiotes cavatus and two four-eyed Miagrammopes species have greater retinal hemisphere areas and lens volumes than do the eight-eyed u…

When visual fields of the primitive orb-weaver, Waitkera waitkerensis, are reconstructed using measurements taken from intact lenses and cross and longitudinal sections of the prosoma, they show that this species has complete visual surveillance, but that none of the visual fields of its eight eyes overlap. The more advanced orb…

Members of the genera Uloborus, Hyptiotes, and Miagrammopes have similar web-monitoring postures, but very different webs and tactics for monitoring them. Orb weavers of the genus Uloborus construct horizontal webs and hang from their hubs, whereas reduced-web uloborids construct vertical webs and monitor them from a single thre…

Observations of 22 orb-weaving species of the family Uloboridae show that these spiders assume one of four basic resting postures as they hang beneath the web's hub. The primitive pattern found in Tangaroa and Octonoba is characterized by all legs being spread and about equally flexed, whereas in Zosis the protracted first legs…

In the family Uloboridae, web reduction is associated with changes in web monitoring posture and prosomal features. A spider must extend its first pair of legs directly forward to monitor the signal line of a reduced web. This posture is facilitated by shifts in prosomal musculature that cause reduced web uloborids to have a nar…

Uloborid cribellar silk consists of torus-shaped puffs. In Miagrammopes animotus the width of these puffs is about 36% that of the cribellum of the spider and shows a 2.3-fold increase in surface area during development. The cribellar spigot number increase 5.7-fold during development, although, relative to spider mass, it decre…