Euryattus

Abstract: The biology of an aberrant saltioid spider, Euryattus Thorell sp indet, is described from observations in a Queensland rain forest and the laboratory Pronounced morphological and behavioural changes occur during post-embryological development Juveniles spin webs, but adult females make ‘suspension nests’ by suspending a curled-up leaf by heavy guylines from a rock ledge or vegetation Adult males spin neither webs nor suspension nests Females oviposit inside their suspension nests, but if denied access to leaves for suspension, they spin and oviposit in webs similar to those spun by juveniles The flat, papery egg sacs of Euryattus are atypical for a salticid, being more like the egg sacs of many of the Gnaphosidae Intraspecific display behaviour has characteristics in common with typical salticids, but also includes unique features Male courtship includes vibratory displays performed on the surface of the suspended leaf Mating occurs inside the curled-up leaf Males co-habit with sub-adult females in suspension nests Females take over suspension nests of other females and eat each other's eggs Normal locomotion, intraspecific interactions, and predatory behaviour are characterized by frequent leaping Euryattus routinely makes long and accurate leaps on to prey, including flying insects intercepted in mid-air and spiders and insects located in alien webs The phylogenetic implications of the unusual characteristics of Euryattus are considered

Abstract: Psilochorus sphaeroides from Queensland, Australia and Smeringopus pallidus from Sri Lanka are long-legged, web-building pholcid spiders with a special defence behaviour, whirling. The efficiency of whirling as a defence against web-invading jumping spiders (Salticidae) was examined in the laboratory. Three salticid species were used in these tests-Euryattus sp., Portia fimbriata and Portia labiata. Euryattus leapt into webs, but Portia fimbriata and Portia labiata walked slowly into webs and practised aggressive mimicry. Portia fimbriata was more consistent at using aggressive mimicry and more efficient at capturing Psilochorus sphaeroides and Smeringopus pallidus than was Portia labiata. Both species of Portia were more efficient at catching pholcids than was Euryattus. Portia, especially Portia fimbriata, was less inclined than Euryattus to stimulate pholcids to whirl. In an experiment in which pholcids were artificially induced to whirl whenever a salticid was near, salticids never captured pholcids, providing additional evidence that whirling is an effective defence of Psilochorus sphaeroides and Smeringopus pallidus against web-invaders. Results from this study are compared to those from a study of another pholcid that whirls, Pholcus phalangioides.

Abstract: The retinal ultrastructure of an aberrant salticid spider, Euryattus bleekeri (Doleschall, 1859) is described, and discussed in the context of a model of the evolution of the Salticidae previously proposed by Jackson & Blest (1982a) The evolutionary model suggested that the Salticidae are derived from web-building ancestors that acquired the strategy of invading the webs of other species and families of spiders; it predicts that the evolution of the principal eyes preceded that of the accessory eyes, and that traces of this sequence of events should be observable in contemporary forms Euryattus exhibits an unusual pattern of web-dependency (Jackson, 1985) The principal eyes conform to those of ‘advanced’ Salticidae, but the anterior lateral eyes exhibit two features associated, so far, with the primitive Spartaeinae: transverse sections of the rhabdoms present rectangular (rather than circular) profiles, and the non-pigmented glial cytoplasm is depleted of microtubules These findings marginally support a case for Euryattus having primitive affinities, but their import is ambiguous, and the evidence cannot be regarded as conclusive Possible affinities between the Gnaphosidae and Salticidae based upon common tactics of web-invasion are qualified by a comment on the retinae of the two families