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Geoffrey K Isbister - One of the best experts on this subject based on the ideXlab platform.

  • Clinical consequences of Spider bites: recent advances in our understanding
    Toxicon, 2004
    Co-Authors: Geoffrey K Isbister, Julian White
    Abstract:

    Spider bite continues to be a controversial subject worldwide and attribution of clinical effects to different Spiders is problematic because of poor case definition and paucity of clinical evidence. The effects of medically important Spiders are sometimes underestimated and simultaneously there is misattribution of effects to harmless Spider groups. The majority of suspected Spider bites present as skin lesions or necrotic ulcers where the history of a Spider bite must be confirmed. To be a definite Spider bite, the patient must immediately observe the Spider and there be evidence of the bite, such as pain. Important groups of Spiders worldwide include the widow Spiders (latrodectism), recluse Spiders (loxoscelism) and some mygalomorph Spiders including the Australian Funnel web Spider. Most Spiders only cause minor effects, including a large number of groups that have been implicated in necrotic arachnidism.

  • Developing a decision tree algorithm for the diagnosis of suspected Spider bites
    Emergency Medicine Australasia, 2004
    Co-Authors: Geoffrey K Isbister, David Sibbritt
    Abstract:

    Objective:  To develop a diagnostic algorithm (decision tree) to improve the ability to identify or predict medically important Spider bites (funnel-web and redback Spiders) from information about the circumstances and initial clinical effects of Spider bites. Methods:  A dataset of definite Spider bites with expert identification of all Spiders was used from a previous Australia-wide prospective study. Spider bites were categorized as: big black Spider (BBS), redback Spider (RED) and other Spider (OTH). Big black Spider included funnel-web Spiders (most medically significant), but also other Spiders of similar appearance. Fifteen predictor variables were based on univariate analysis from previous studies and clinical experience. They included information about the circumstances and early clinical effects of bites. The data were analyzed using CART® (Classification and Regression Trees), a ‘decision tree’ algorithm used to create a tree-like structure to describe a data set. Results:  Of 789 Spider bites there were 49 (6.2%) bites by BBS, 68 (8.6%) bites by RED and 672 (85.2%) bites by OTH. A decision tree was developed that included six predictor variables (fang marks/bleeding; state/territory; local diaphoresis; month; time of day; and proximal or distal bite region). The decision tree accurately classified 47 out of the 49 (96%) BBS, and no funnel-web Spiders were incorrectly classified (100% sensitivity). Two hundred and forty-four of 789 were classified as OTH and included no BBS. Conclusions:  A decision tree based on a small amount of information about the circumstances and early clinical effects of Spider bites safely predicted all funnel-web Spider bites. Application of this algorithm would allow the early institution of appropriate treatment for funnel-web Spider bites and the immediate discharge of 31% as other Spider bites (reassurance only).

  • Bites by Australian mygalomorph Spiders (Araneae, Mygalomorphae), including funnel-web Spiders (Atracinae) and mouse Spiders (Actinopodidae: Missulena spp).
    Toxicon : official journal of the International Society on Toxinology, 2004
    Co-Authors: Geoffrey K Isbister, Michael R Gray
    Abstract:

    A number of mygalomorph Spiders cause bites in Australia, including the funnel-web Spiders (Hexathelidae, Atracinae: Hadronyche and Atrax) and mouse Spiders (Actinopodidae: Missulena). There is ongoing debate about the significance of bites by mouse Spiders and the frequency of severe envenoming by funnel-web Spiders. We conducted a prospective cohort study of definite Spider bites with expert Spider identification and include the analysis of mygalomorph Spiders here. Subjects were recruited prospectively from February 1999 to April 2003 from patients presenting to participating hospitals or contacting a state poison information centre. Forty-nine cases of bites by mygalomorph Spiders were included: 16 were by funnel-web Spiders, 13 by mouse Spiders and 20 by other trapdoor Spiders (Families Idiopidae and Nemesiidae). Of the 49 bites, 45 (92%) occurred on distal limbs (hands and feet). Local effects included severe pain (53%), puncture marks (61%) and bleeding (27%), local redness (33%). Itchiness did not occur. The following were highly statistically associated with mygalomorph Spider bites compared to all other Spiders (p

  • bites by Spiders of the family theraphosidae in humans and canines
    Toxicon, 2003
    Co-Authors: Geoffrey K Isbister, Jamie Seymour, Michael R Gray, Robert J Raven
    Abstract:

    Spiders of the family Theraphosidae occur throughout most tropical regions of the world. There have only been three case reports of bites by these Spiders in Australia. The aim of this study was to describe the clinical effects of bites by Australian theraphosid Spiders in both humans and canines. Cases of Spider bite were collected by the authors over the period January 1978–April 2002, either prospectively in a large study of Australian Spider bites, or retrospectively from cases reported to the authors. Subjects were included if they had a definite bite and had collected the Spider. The Spiders were identified by an expert arachnologist to genus and species level where possible. There were nine confirmed bites by Spiders of the family Theraphosidae in humans and seven in canines. These included bites by two Selenocosmia spp. and by two Phlogiellus spp. The nine Spider bites in humans did not cause major effects. Local pain was the commonest effect, with severe pain in four of seven cases where severity of pain was recorded. Puncture marks or bleeding were the next most common effect. In one case the Spider had bitten through the patient's fingernail. Mild systemic effects occurred in one of nine cases. There were seven bites in dogs (Phlogellius spp. and Selenocosmia spp.), and in two of these the owner was bitten after the dog. In all seven cases the dog died, and as rapidly as 0.5–2 h after the bite. This small series of bites by Australian theraphosid Spiders gives an indication of the spectrum of toxicity of these Spiders in humans. Bites by these Spiders are unlikely to cause major problems in humans. The study also demonstrates that the venom is far more toxic to canines.

  • A prospective study of 750 definite Spider bites, with expert Spider identification
    QJM: An International Journal of Medicine, 2002
    Co-Authors: Geoffrey K Isbister, Michael R Gray
    Abstract:

    Summary Background: Spider bite is a subject of much medical mythology with prevalent fears that Spiders cause severe envenoming, with neurotoxic effects or necrotic ulcers. Clinical experience and small studies suggest otherwise, but this has not been confirmed by prospective studies of bites by identified Spiders. Aim: To describe the clinical effects of bites by accurately identified Spiders, and determine whether early clinical features and circumstances can predict Spider type. Design: Prospective follow-up study. Methods: Patients were recruited from admissions to two emergency departments (n=48) and referrals from three state poison information centres (n=1426), over 27 months. Overall, there were 750 people with definite Spider bites where the Spiders were immediately collected and expertly identified. Results: Significant effects occurred in 44 bites (6%), including 37 (of 56) redback Spider bites (Latrodectus hasselti) with significant pain lasting )24 h. Of these, only 6 (11%) received antivenom. One severe neurotoxic envenoming by an Australian funnelweb Spider required antivenom. No definite Spider bites resulted in necrotic ulcers (0%, 99%CI 0–0.7%). There were no early allergic reactions and secondary infection occurred in seven cases (0.9% ,9 5%CI 0.4–1.9%). Circumstances and early clinical effects were strongly associated with taxonomic Spider identification, with positive predictive values )0.95 for common groups of Spiders. Conclusions: Australian Spider bite caused minor effects in most cases and is unlikely to cause necrotic ulcers, allergic reactions or infection. Redback Spider bite (widow Spider) caused prolonged pain, and antivenom could have been used more frequently. The circumstances and early clinical features of Spider bites may allow early appropriate advice and treatment of Spider bite without taxonomic identification.

Martin Nyffeler - One of the best experts on this subject based on the ideXlab platform.

  • An estimated 400–800 million tons of prey are annually killed by the global Spider community
    The Science of Nature, 2017
    Co-Authors: Martin Nyffeler, Klaus Birkhofer
    Abstract:

    Spiders have been suspected to be one of the most important groups of natural enemies of insects worldwide. To document the impact of the global Spider community as insect predators, we present estimates of the biomass of annually killed insect prey. Our estimates assessed with two different methods suggest that the annual prey kill of the global Spider community is in the range of 400–800 million metric tons (fresh weight), with insects and collembolans composing >90% of the captured prey. This equals approximately 1‰ of the global terrestrial net primary production. Spiders associated with forests and grasslands account for >95% of the annual prey kill of the global Spider community, whereas Spiders in other habitats are rather insignificant contributors over a full year. The Spider communities associated with annual crops contribute less than 2% to the global annual prey kill. This, however, can be partly explained by the fact that annual crop fields are “disturbed habitats” with a low buildup of Spider biomass and that agrobiont Spiders often only kill prey over short time periods in a year. Our estimates are supported by the published results of exclusion experiments, showing that the number of herbivorous/detritivorous insects and collembolans increased significantly after Spider removal from experimental plots. The presented estimates of the global annual prey kill and the relative contribution of Spider predation in different biomes improve the general understanding of Spider ecology and provide a first assessment of the global impact of this very important predator group.

  • an estimated 400 800 million tons of prey are annually killed by the global Spider community
    Naturwissenschaften, 2017
    Co-Authors: Martin Nyffeler, Klaus Birkhofer
    Abstract:

    Spiders have been suspected to be one of the most important groups of natural enemies of insects worldwide. To document the impact of the global Spider community as insect predators, we present estimates of the biomass of annually killed insect prey. Our estimates assessed with two different methods suggest that the annual prey kill of the global Spider community is in the range of 400–800 million metric tons (fresh weight), with insects and collembolans composing >90% of the captured prey. This equals approximately 1‰ of the global terrestrial net primary production. Spiders associated with forests and grasslands account for >95% of the annual prey kill of the global Spider community, whereas Spiders in other habitats are rather insignificant contributors over a full year. The Spider communities associated with annual crops contribute less than 2% to the global annual prey kill. This, however, can be partly explained by the fact that annual crop fields are “disturbed habitats” with a low buildup of Spider biomass and that agrobiont Spiders often only kill prey over short time periods in a year. Our estimates are supported by the published results of exclusion experiments, showing that the number of herbivorous/detritivorous insects and collembolans increased significantly after Spider removal from experimental plots. The presented estimates of the global annual prey kill and the relative contribution of Spider predation in different biomes improve the general understanding of Spider ecology and provide a first assessment of the global impact of this very important predator group.

  • Fish predation by semi-aquatic Spiders: a global pattern.
    PloS one, 2014
    Co-Authors: Martin Nyffeler, Bradley James Pusey
    Abstract:

    More than 80 incidences of fish predation by semi-aquatic Spiders – observed at the fringes of shallow freshwater streams, rivers, lakes, ponds, swamps, and fens – are reviewed. We provide evidence that fish predation by semi-aquatic Spiders is geographically widespread, occurring on all continents except Antarctica. Fish predation by Spiders appears to be more common in warmer areas between 40° S and 40° N. The fish captured by Spiders, usually ranging from 2–6 cm in length, are among the most common fish taxa occurring in their respective geographic area (e.g., mosquitofish [Gambusia spp.] in the southeastern USA, fish of the order Characiformes in the Neotropics, killifish [Aphyosemion spp.] in Central and West Africa, as well as Australian native fish of the genera Galaxias, Melanotaenia, and Pseudomugil). Naturally occurring fish predation has been witnessed in more than a dozen Spider species from the superfamily Lycosoidea (families Pisauridae, Trechaleidae, and Lycosidae), in two species of the superfamily Ctenoidea (family Ctenidae), and in one species of the superfamily Corinnoidea (family Liocranidae). The majority of reports on fish predation by Spiders referred to pisaurid Spiders of the genera Dolomedes and Nilus (>75% of observed incidences). There is laboratory evidence that Spiders from several more families (e.g., the water Spider Argyroneta aquatica [Cybaeidae], the intertidal Spider Desis marina [Desidae], and the ‘swimming’ huntsman Spider Heteropoda natans [Sparassidae]) predate fish as well. Our finding of such a large diversity of Spider families being engaged in fish predation is novel. Semi-aquatic Spiders captured fish whose body length exceeded the Spiders’ body length (the captured fish being, on average, 2.2 times as long as the Spiders). Evidence suggests that fish prey might be an occasional prey item of substantial nutritional importance.

Robert R. Jackson - One of the best experts on this subject based on the ideXlab platform.

  • Specialised use of working memory by Portia africana, a Spider-eating salticid
    Animal cognition, 2013
    Co-Authors: Fiona R. Cross, Robert R. Jackson
    Abstract:

    Using expectancy–violation methods, we investigated the role of working memory in the predatory strategy of Portia africana, a salticid Spider from Kenya that preys by preference on other Spiders. One of this predator’s tactics is to launch opportunistic leaping attacks on to other Spiders in their webs. Focussing on this particular tactic, our experiments began with a test Spider on a ramp facing a lure (dead prey Spider mounted on a cork disc) that could be reached by leaping. After the test Spider faced the lure for 30 s, we blocked the test Spider’s view of the lure by lowering an opaque shutter before the Spider leapt. When the shutter was raised 90 s later, either the same lure came into view again (control) or a different lure came into view (experimental: different prey type in same orientation or same prey type in different orientation). We recorded attack frequency (number of test Spiders that leapt at the lure) and attack latency (time elapsing between shutter being raised and Spiders initiating a leap). Attack latencies in control trials were not significantly different from attack latencies in experimental trials, regardless of whether it was prey type or prey orientation that changed in the experimental trials. However, compared with test Spiders in the no-change control trials, significantly fewer test Spiders leapt when prey type changed. There was no significant effect on attack frequency when prey orientation changed. These findings suggest that this predator represents prey type independently of prey orientation.

  • Cues for web invasion and aggressive mimicry signalling in Portia (Araneae, Salticidae)
    Journal of Zoology, 1995
    Co-Authors: Robert R. Jackson
    Abstract:

    Portia is a web-invading araneophagic Spider that uses aggressive mimicry to deceive its prey. The present paper is a first step toward clarifying experimentally the cues that govern Portia's decisions of whether to enter a web, whether to make signals once in a web, and whether to persist at signalling once started. The following conclusions are supported: cues from seeing a web elicit web entry, but volatile chemical cues from webs of prey Spiders are not important; seeing a Spider in a web increases Portia's inclination to enter the web; after web entry, cues from webs of prey Spiders are sufficient to elicit signalling behaviour, even in the absence of other cues coming directly from the prey Spider; seeing a prey Spider or detecting vibrations on the web make Portia more prone to signal, but volatile chemical cues from prey Spiders are not important; once Portia is on a web and signalling, seeing a moving Spider and detecting vibrations on the web encourage Portia to persist in signalling; on the basis of visual cues alone, Portia can distinguish between quiescent Spiders, insects and eggsacs.

  • Spider flexibly chooses aggressive mimicry signals for different prey by trial and error
    Behaviour, 1993
    Co-Authors: Robert R. Jackson, R. Stimson Wilcox
    Abstract:

    Portia is a jumping Spider that invades other Spiders' webs, makes vibratory signals that deceive the resident Spider (aggressive mimicry), then attacks and eats the Spider. Portia exploits a wide range of prey-Spider species. Evidence is provided from observation and experimentation that Portia uses a trial-and-error method as part of its strategy for deriving appropriate signals for different prey. To use this method, Portia first broadcasts an array of different signals, then narrows to particular signals as a consequence of feedback from the prey Spider. Feedback can be web vibration or seeing Spiders move, or both. This appears to be an example of deception involving at least a limited form of learning, an uncommon phenomenon in invertebrates.

  • Spider Behaviour: Flexibility in the foraging strategies of Spiders
    Spider Behaviour, 1
    Co-Authors: Ximena J. Nelson, Robert R. Jackson
    Abstract:

    Although many Spiders build prey-capture webs, Spider foraging strategies include species that, instead of building webs, deploy silk in other ways for prey capture. Additionally, there are species that capture prey, either by ambush or by active pursuit, without making notable use of silk in the process. There are striking examples of predatory specialisation from Spiders, particularly among the Salticidae, suggesting that assumptions about adaptive trade-offs, in which the small nervous systems of Spiders might constrain their cognitive or sensory abilities, need to be carefully evaluated. Predatory versatility, whereby an individual Spider adopts a conditional strategy with which it classifies prey into diverse categories, illustrates that an individual Spider may be a poly-specialist, because it is polyphagic and at the same time it is highly specialised on more than one prey type. More generally, individual flexibility in Spider behaviour has important implications concerning the cognitive capacities of predators that orchestrate their strategies using small nervous systems. Introduction At first glance, characterising Spider foraging might appear straightforward. All Spiders are predators, and most frequently the Spider's prey is an insect. All Spiders produce silk, which is often put to use as part of their predatory arsenal. Yet a closer look reveals staggering diversity – and it is not just variation between species that contributes to this diversity, as we also need to address variation within single species and even within individual Spiders.

Richard S. Vetter - One of the best experts on this subject based on the ideXlab platform.

  • Verified Spider bites in Oregon (USA) with the intent to assess hobo Spider venom toxicity.
    Toxicon, 2014
    Co-Authors: Nathanael J Mckeown, Richard S. Vetter, Robert G Hendrickson
    Abstract:

    Abstract This study compiled 33 verified Spider bites from the state of Oregon (USA). The initial goal was to amass a series of bites by the hobo Spider to assess whether it possesses toxic venom, a supposition which is currently in a contested state. None of the 33 bites from several Spider species developed significant medical symptoms nor did dermonecrosis occur. The most common biters were the yellow sac Spider, Cheiracanthium mildei ( N  = 10) and orb-weavers of the genus Araneus ( N  = 6). There were 10 bites from three genera of funnel web Spiders of the family Agelenidae including one hobo Spider bite and one from the congeneric giant house Spider which is readily confused as a hobo Spider. The hobo Spider bite resulted in pain, redness, twitching in the calf muscle and resolved in 12 h. Also generated from this study were possibly the first records of bites from Spiders of the genera Callobius (Amaurobiidae) and Antrodiaetus (Antrodiaetidae), both with minor manifestations.

  • An approach to Spider bites. Erroneous attribution of dermonecrotic lesions to brown recluse or hobo Spider bites in Canada.
    Canadian Family Physician, 2004
    Co-Authors: Robert G. Bennett, Richard S. Vetter
    Abstract:

    OBJECTIVE To dispel prevalent myths surrounding diagnosis of dermonecrotic and associated conditions supposedly resulting from bites of brown recluse, hobo, or other Spiders in Canada. SOURCES OF INFORMATION Worldwide, Spider bites are regularly misdiagnosed as the etiologic agents in human dermonecrosis mainly as a result of inaccurate, erroneous, or hyperbolic popular and professional literature based on inference, circumstantial evidence, inferior clinical trials, and misunderstanding of the facts regarding Spider-bite envenomation. MAIN MESSAGE A working diagnosis of “Spider bite” or publishing a case history should be considered only when a Spider is caught in the act of biting or otherwise reliably associated with a lesion. Accurate identifi cation of the Spider could be critical for correct diagnosis and subsequent treatment. CONCLUSION Brown recluse Spiders are not found in Canada. Hobo Spiders have not been reliably implicated in dermonecrosis. Worldwide, Spider-bite envenomation is an unlikely cause of dermonecrosis. Canadian physicians should give priority consideration to other, more likely, causes. RESUME

  • Reports of envenomation by brown recluse Spiders (Araneae: Sicariidae) outnumber verifications of Loxosceles Spiders in Florida.
    Journal of medical entomology, 2004
    Co-Authors: Richard S. Vetter, G. B. Edwards, Louis F. James
    Abstract:

    Abstract Bites attributed to the brown recluse Spider, Loxosceles reclusa Gertsch & Mulaik, are frequently reported by medical personnel throughout Florida, whereas the extensive arachnological evidence contradicts the alleged widespread occurrence of Loxosceles Spiders in the state. We compared reports of brown recluse Spider bites made by medical personnel from a 6-yr Florida poison control center database to the known verifications of Loxosceles Spiders from 100 yr of Florida arachnological data. Medical personnel diagnosed 124 brown recluse Spider bites from 31 of Florida’s 67 counties in 6 yr. In contrast, only 11 finds of ≈70 Loxosceles Spiders have been made in 10 Florida counties in 100 yr. Florida does not have sufficient widespread populations of Loxosceles Spiders to warrant consideration of brown recluse Spider envenomation as a probable etiology of dermonecrosis. Florida health care would improve if medical personnel would consider the multitude of other etiologies that manifest in dermonecrosis.

  • Reports of Presumptive Brown Recluse Spider Bites Reinforce Improbable Diagnosis in Regions of North America Where the Spider Is Not Endemic
    Clinical infectious diseases : an official publication of the Infectious Diseases Society of America, 2002
    Co-Authors: Richard S. Vetter, Sean P. Bush
    Abstract:

    Envenomations by the brown recluse Spider have been reported throughout North America, despite the fact that the Spider's range is limited to the South and central Midwest of the United States. Several of these medical reports have originated from regions of nonendemicity where the Spider has never or rarely been documented and brown recluse Spider populations are unknown. In most of these reports, no Spider is positively identified in association with the dermonecrotic wound, and diagnosis has been based on clinical examination findings. Considering the extreme rarity of brown recluse Spiders in areas of nonendemicity, the diagnosis of a presumptive bite is a misdiagnosis that reinforces the assumption that brown recluse Spiders are common local etiologic agents of necrosis. There are many medical conditions of diverse origin that have been misdiagnosed as brown recluse Spider bites, some of which can be fatal or debilitating. Physicians' awareness of these conditions will increase diagnostic accuracy in areas of North America where bites from brown recluse Spiders are improbable.

Michael R Gray - One of the best experts on this subject based on the ideXlab platform.

  • Bites by Australian mygalomorph Spiders (Araneae, Mygalomorphae), including funnel-web Spiders (Atracinae) and mouse Spiders (Actinopodidae: Missulena spp).
    Toxicon : official journal of the International Society on Toxinology, 2004
    Co-Authors: Geoffrey K Isbister, Michael R Gray
    Abstract:

    A number of mygalomorph Spiders cause bites in Australia, including the funnel-web Spiders (Hexathelidae, Atracinae: Hadronyche and Atrax) and mouse Spiders (Actinopodidae: Missulena). There is ongoing debate about the significance of bites by mouse Spiders and the frequency of severe envenoming by funnel-web Spiders. We conducted a prospective cohort study of definite Spider bites with expert Spider identification and include the analysis of mygalomorph Spiders here. Subjects were recruited prospectively from February 1999 to April 2003 from patients presenting to participating hospitals or contacting a state poison information centre. Forty-nine cases of bites by mygalomorph Spiders were included: 16 were by funnel-web Spiders, 13 by mouse Spiders and 20 by other trapdoor Spiders (Families Idiopidae and Nemesiidae). Of the 49 bites, 45 (92%) occurred on distal limbs (hands and feet). Local effects included severe pain (53%), puncture marks (61%) and bleeding (27%), local redness (33%). Itchiness did not occur. The following were highly statistically associated with mygalomorph Spider bites compared to all other Spiders (p

  • bites by Spiders of the family theraphosidae in humans and canines
    Toxicon, 2003
    Co-Authors: Geoffrey K Isbister, Jamie Seymour, Michael R Gray, Robert J Raven
    Abstract:

    Spiders of the family Theraphosidae occur throughout most tropical regions of the world. There have only been three case reports of bites by these Spiders in Australia. The aim of this study was to describe the clinical effects of bites by Australian theraphosid Spiders in both humans and canines. Cases of Spider bite were collected by the authors over the period January 1978–April 2002, either prospectively in a large study of Australian Spider bites, or retrospectively from cases reported to the authors. Subjects were included if they had a definite bite and had collected the Spider. The Spiders were identified by an expert arachnologist to genus and species level where possible. There were nine confirmed bites by Spiders of the family Theraphosidae in humans and seven in canines. These included bites by two Selenocosmia spp. and by two Phlogiellus spp. The nine Spider bites in humans did not cause major effects. Local pain was the commonest effect, with severe pain in four of seven cases where severity of pain was recorded. Puncture marks or bleeding were the next most common effect. In one case the Spider had bitten through the patient's fingernail. Mild systemic effects occurred in one of nine cases. There were seven bites in dogs (Phlogellius spp. and Selenocosmia spp.), and in two of these the owner was bitten after the dog. In all seven cases the dog died, and as rapidly as 0.5–2 h after the bite. This small series of bites by Australian theraphosid Spiders gives an indication of the spectrum of toxicity of these Spiders in humans. Bites by these Spiders are unlikely to cause major problems in humans. The study also demonstrates that the venom is far more toxic to canines.

  • A prospective study of 750 definite Spider bites, with expert Spider identification
    QJM: An International Journal of Medicine, 2002
    Co-Authors: Geoffrey K Isbister, Michael R Gray
    Abstract:

    Summary Background: Spider bite is a subject of much medical mythology with prevalent fears that Spiders cause severe envenoming, with neurotoxic effects or necrotic ulcers. Clinical experience and small studies suggest otherwise, but this has not been confirmed by prospective studies of bites by identified Spiders. Aim: To describe the clinical effects of bites by accurately identified Spiders, and determine whether early clinical features and circumstances can predict Spider type. Design: Prospective follow-up study. Methods: Patients were recruited from admissions to two emergency departments (n=48) and referrals from three state poison information centres (n=1426), over 27 months. Overall, there were 750 people with definite Spider bites where the Spiders were immediately collected and expertly identified. Results: Significant effects occurred in 44 bites (6%), including 37 (of 56) redback Spider bites (Latrodectus hasselti) with significant pain lasting )24 h. Of these, only 6 (11%) received antivenom. One severe neurotoxic envenoming by an Australian funnelweb Spider required antivenom. No definite Spider bites resulted in necrotic ulcers (0%, 99%CI 0–0.7%). There were no early allergic reactions and secondary infection occurred in seven cases (0.9% ,9 5%CI 0.4–1.9%). Circumstances and early clinical effects were strongly associated with taxonomic Spider identification, with positive predictive values )0.95 for common groups of Spiders. Conclusions: Australian Spider bite caused minor effects in most cases and is unlikely to cause necrotic ulcers, allergic reactions or infection. Redback Spider bite (widow Spider) caused prolonged pain, and antivenom could have been used more frequently. The circumstances and early clinical features of Spider bites may allow early appropriate advice and treatment of Spider bite without taxonomic identification.