Review of the Australian and New Zealand orb-weaving spider genus Novakiella (Araneae, Araneidae)

The orb-weaving spider genus Novakiella Court & Forster, 1993 (family Araneidae Clerck, 1757) is reviewed to include two species, N. trituberculosa (Roewer, 1942) (type species, Australia and New Zealand) and N. boletus sp. nov. (Australia). Novakiella belongs to the informal, largely Australian ‘backobourkiine’ clade and shares with the other genera of the clade a single macroseta on the male pedipalp patella and a median apophysis of the male pedipalp that forms an arch over the radix. The proposed genus synapomorphies are the presence of a large basal conductor lobe expanding apically over the radix and the shape of the median apophysis, which extends into a basally directed, pointy projection. Males have an apico-prolateral spur on the tibia of the second leg that carries a distinct spine. Females have an epigyne with triangular base plate bearing transverse ridges and an elongate triangular scape, which is almost always broken off. The humeral humps of the abdomen are distinct. Novakiella trituberculosa build characteristic dome-shaped webs; however, the foraging behaviour and web-shape of N. boletus sp. nov., currently only known from museum specimens, are not known

Morphological Evolution of Spiders Predicted by Pendulum Mechanics

[Background] Animals have been hypothesized to benefit from pendulum mechanics during suspensory locomotion, in which the potential energy of gravity is converted into kinetic energy according to the energy-conservation principle. However, no convincing evidence has been found so far. Demonstrating that morphological evolution follows pendulum mechanics is important from a biomechanical point of view because during suspensory locomotion some morphological traits could be decoupled from gravity, thus allowing independent adaptive morphological evolution of these two traits when compared to animals that move standing on their legs; i.e., as inverted pendulums. If the evolution of body shape matches simple pendulum mechanics, animals that move suspending their bodies should evolve relatively longer legs which must confer high moving capabilities.[Methodology/Principal Findings] We tested this hypothesis in spiders, a group of diverse terrestrial generalist predators in which suspensory locomotion has been lost and gained a few times independently during their evolutionary history. In spiders that hang upside-down from their webs, their legs have evolved disproportionately longer relative to their body sizes when compared to spiders that move standing on their legs. In addition, we show how disproportionately longer legs allow spiders to run faster during suspensory locomotion and how these same spiders run at a slower speed on the ground (i.e., as inverted pendulums). Finally, when suspensory spiders are induced to run on the ground, there is a clear trend in which larger suspensory spiders tend to run much more slowly than similar-size spiders that normally move as inverted pendulums (i.e., wandering spiders).[Conclusions/Significance] Several lines of evidence support the hypothesis that spiders have evolved according to the predictions of pendulum mechanics. These findings have potentially important ecological and evolutionary implications since they could partially explain the occurrence of foraging plasticity and dispersal constraints as well as the evolution of sexual size dimorphism and sociality.This paper has been written under a Ramón y Cajal research contract from the Spanish Ministry of Science and Culture (MEC) to JML and a FPI scholarship (BES-2005-9234) to GC. This work has been funded by MEC grants CGL2004-03153 and CGL2007-60520 to JML and GC, as well as CGL2005-01771 to EMPeer reviewe

The scorpion-tailed orb-weaving spiders (Araneae, Araneidae, Arachnura) in Australia and New Zealand

The scorpion-tailed orb-weaving spiders in the genus Arachnura Vinson, 1863 (Araneidae Clerck, 1757) are revised for Australia and New Zealand. Arachnura higginsii (L. Koch, 1872) only occurs in Australia and A. feredayi (L. Koch, 1872) only in New Zealand. A single female collected in south-eastern Queensland (Australia) is here tentatively identified as A. melanura Simon, 1867, but it is doubtful that this species has established in Australia. Two juveniles from northern Queensland do not conform to the diagnoses of any of the above species and are illustrated pending a more thorough revision of the genus in South-East Asia and the Pacific region. An unidentified female from Westport (New Zealand) does not conform to the diagnoses of A. feredayi and A. higginsii, but is not described due to its poor preservation status. Arachnura caudatella Roewer, 1942 (replacement name for Epeira caudata Bradley, 1876), originally described from Hall Sound (Papua New Guinea) and repeatedly catalogued for Australia, is considered a nomen dubium