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Although a wide range of vertebrates have been considered in research on numerical competence, little is known about the role of number-related decisions in the predatory strategies of invertebrates. Here, we investigate how numerical competence is expressed in a highly specialized predatory strategy adopted by the small juveniles of Portia africana when practicing communal predation, with the prey being another spider, Oecobius amboseli. Two or more P. africana juveniles sometimes settle by the same oecobiid nest and then share the meal after one individual captures the oecobiid. Experiments were designed to clarify how these predators use number-related cues in conjunction with non-numerical cues when deciding whether to settle at a nest. We used lures (dead spiders positioned in lifelike posture) arranged in a series of 24 different scenes defined by the type, configuration and especially number of lures. On the whole, our findings suggest that P. africana juveniles base settling decisions on the specific number of already settled conspecific juveniles at the nest and express a preference for settling when the number is one instead of zero, two or three. By varying the size of the already settled juveniles and their positions around the nest, we show that factors related to continuous variables and stimulus configuration are unlikely explanations for our findings. [ABSTRACT FROM AUTHOR]

Among spiders, resemblance of ants (myrmecomorphy) usually involves the Batesian mimicry, in which the spider coopts the morphological and behavioural characteristics of ants to deceive ant-averse predators. Nevertheless, the degree of resemblance between mimics and ants varies considerably. I used Portia fimbriata, a jumping spider (Salticidae) with exceptional eyesight that specialises on preying on salticids, to test predator perception of the accuracy of ant mimicry. Portia fimbriata's response to ants (Oecophylla smaragdina), accurate ant-like salticids (Synageles occidentalis), and inaccurate ant-like salticids (females of Myrmarachne bakeri and sexually dimorphic males of M. bakeri, which have enlarged chelicerae) was assessed. Portia fimbriata exhibited graded aversion in accordance with the accuracy of resemblance to ants (O. smaragdina > S. occidentalis > female M. bakeri > male M. bakeri). These results support the hypothesis that ant resemblance confers protection from visual predators, but to varying degrees depending on signal accuracy. [ABSTRACT FROM AUTHOR]

Jumping spiders (Salticidae) are known for having good eyesight, but the extent to which they also rely on olfaction is poorly understood. We report here new information on the olfactory abilities of the salticid genus Portia. We investigated for the first time the ability of adult males and females of four Portia species (P. africana, P. schultzi, P. fimbriata and P. labiata) to discriminate between mate and non-mate odor. In a Y-shape olfactometer, males of all four species chose the odor from an opposite-sex conspecific significantly more often than they chose a no-odor control, but the number of males that chose the odor from an opposite-sex heterospecific or the odor from a same-sex conspecific was not significantly different from the number of males that chose the control. The number of female test spiders that chose the odor from an opposite-sex conspecific or the odor from a same-sex conspecific was not significantly different from the number of females that chose the control. The implications of these findings for understanding Portia's mating system are discussed. [ABSTRACT FROM AUTHOR]

ll species from the jumping spider (Salticidae) genus Portia appear to be predators that specialize at preying on other spiders by invading webs and, through aggressive mimicry, gaining dynamic fine control over the resident spider's behavior. From previous research, there is evidence that P. fimbriata, P. labiata and P. schultzi derive signals by trial and error. Here, we demonstrate that P. africana is another species that uses a trial and error, or generate and test, algorithm when deriving the aggressive-mimicry signals that will be appropriate in different predator-prey encounters. We discuss the implications of these new findings and the findings from previous work in order to understand the selection factors that drive the evolution of flexibility in aggressive-mimicry strategies. [ABSTRACT FROM AUTHOR]

n important prediction from game theory is that the value of a resource will influence the level to which an animal is willing to escalate during conflict with conspecific rivals. Here we use this prediction as the rationale for experiments aimed at determining whether escalation decisions made by predators are influenced by the presence of preferred prey. The predators we use are adult individuals of Portia fimbriata, a jumping-spider (Salticidae) species from Queensland (Australia). P. fimbriata is known to prefer other salticid species as prey and can detect the odour of Jacksonoides queenslandicus, this being an especially common salticid species in the Queensland habitat. Here we show that, for P. fimbriata females, the odour of J. queenslandicus primes escalation of vision-based conflict. However, for P. fimbriata males, no comparable effect was found. These findings suggest intrasexual competition for prey is more important to females than to males. [ABSTRACT FROM AUTHOR]

Instances are documented of finding individuals of Portia africana in the field living aggregated in the webs of other spiders, in the nest complexes of other salticids, around solitary nests of other salticids, and around the nests of oecobiid spiders. Aggregation members included all active juvenile stages of P. africana, as well as adult males and females. More than one individual of P. africana sometimes fed on the same prey. Small juveniles of P. africana were more often than other stages found aggregated and more often observed feeding together. Small juveniles of P. africana surrounded the nests occupied by other salticid genera and nests occupied by oecobiid spiders. When the resident salticid or oecobiid attempted to leave or enter the nest, one of the P. africana juveniles lunged and captured it, after which other P. africana individuals sometimes joined to feed. [ABSTRACT FROM AUTHOR]

The jumping spider Portia labiata can complete detours in which it must move away from a goal (i.e. prey) before approaching it. This detouring behaviour can be divided into two phases: a scanning phase, during which Portia stays roughly in one spot and examines its environment using its principal eyes, and a locomotory phase, during which Portia performs the detour. Earlier experiments showed that when Portia is initially confined to a small, elevated platform from which it has an unobstructed view of the goal, it plans the initial stage of its detour by scanning the possible route and picking out an unbroken path from start to goal and then aiming at an initial objective along the detour. In the present experiments, I examined the detouring behaviour of P. labiata in an open arena where obstacles provided either indirect access or no access to the goal. Although scanning movements and detour decisions of spiders were similar to those of spiders initially confined to an elevated platform, spiders in the open arena not only scanned at the start but also along the route of the detour. Decision making thus occurred gradually, during both the scanning and the locomotory phases. Taken together, these results and those of previous studies suggest that detouring behaviour in Portia involves a form of vicarious trial and error in which the spider inspects possible routes and selects a series of intermediate goals during both the scanning and locomotory phases of a detour. [Copyright &y& Elsevier]

Portia is a genus of web-invading araneophagic (spider eating) jumping spiders known from earlier studies to derive aggressive-mimicry signals by using a generate-and-test (trial and error) algorithm. We studied individuals of Portia labiata from two populations (Los Baños and Sagada) in the Philippines that have previously been shown to differ in the level to which they rely on trial-and-error derivation of signals for prey capture (Los Baños relied on trial and error more strongly than Sagada P. labiata). Here we investigated P. labiata's use of trial and error in a novel situation (a confinement problem: how to escape from an island surrounded by water) that is unlikely to correspond closely to anything the spider would encounter in nature. During Experiment 1, spiders chose between two potential escape tactics (leap or swim), one of which was set at random to fail (brought spider no closer to edge of tray) and the other of which was set for partially succeeding (brought spider closer to edge of tray). By using trial and error, the Los Baños P. labiata solved the confinement problem significantly more often than the Sagada P. labiata in Experiment I, both when the correct choices were positively reinforced (i.e., when the spider was moved closer to edge of tray) and when incorrect choices were punished (i.e., when the spider got no closer to edge of tray). In Experiment 2, the test individual's first choice was always set to fail, and P. labiata was given repeated opportunities to respond to feedback, yet the Sagada P. labiata continued to place little reliance on trial and error for solving the confinement problem. That the Los Baños P. labiata relied more strongly on trial-and-error problem solving than the Sagada P. labiata has now been demonstrated across two different tasks. [ABSTRACT FROM AUTHOR]

Three species of Portia ( Portia africana from Kenya, Portia fimbriata from Australia and Portia labiata from the Philippines) were tested with flies Drosophila immigrans and Musca domestica and with web-building spiders Badumna longinquus and Pholcus phalangioides. Badumna longinquus has powerful chelicerae, but not especially long legs, whereas Ph. phalangioides has exceptionally long legs, but only small, weak chelicerae. Typically, Portia sighted flies, walked directly towards them and attacked without adjusting orientation. However, Portia's attacks on the spiders were aimed primarily at the cephalothorax instead of the legs or abdomen. Portia usually targeted the posterior-dorsal region of B. longinquus' cephalothorax by attacking this species from above and behind. When the prey was Ph. phalangioides, attack orientation was defined primarily by opportunistic gaps between this species' long legs (gaps through which Portia could contact the pholcid's body without contacting one of the pholcid's legs). Portia's attack strategy appears to be an adjustment to the different types of risk posed by different types of prey. [ABSTRACT FROM AUTHOR]

Jumping spiders have long been known to have large principal eyes with ultraviolet (UV) receptors, and many species of their arthropod prey have body parts that reflect strongly in the UV waveband. However, no attempt has been made to investigate the effects of UV cues from prey on the foraging behaviour of jumping spiders. We performed laboratory experiments to test the hypothesis that jumping spiders use UV cues for locating and discriminating prey. We used Portia labiata, a web-invading, spider-eating jumping spider, as the predator and Argiope versicolor, an orb-web-building spider that decorates its web with UV-reflecting silk stabilimenta, as prey. Portia labiata could detect the difference between UV-reflecting and non-UV-reflecting stabilimentum-decorated webs and they preferentially approached the UV-reflecting ones. These findings may have wide implications for studies of animal foraging, and support one hypothesized function of salticid UV vision, the role of which is largely unknown. [Copyright &y& Elsevier]

Many orb-web weaving spiders add conspicuous silken structures, called stabilimenta, to the hub of their webs, which are hypothesized to attract more prey. However, they may also attract predators. Orb spiders should therefore alter their web-building behaviour to minimize predation risk. We tested this hypothesis by experimentally examining web-building responses of the St Andrew cross spider, Argiope versicolor, to predation risk from one of its natural predators, the jumping spider Portia labiata. We randomly assigned A. versicolor juveniles to one of three treatments: (1) blank control (clean blotting paper: no odour from the predator or nonpredator); (2) predator odour cues from P. labiata; and (3) nonpredator control (odour cues from Leucauge decorata). Each individual of A. versicolor was monitored until it had built five consecutive webs (two webs before and three webs after the introduction of predator cues). When exposed to predator cues, the juveniles not only decreased the frequency of stabilimentum building but also refrained from increasing stabilimentum area, capture area and capture silk thread with subsequent webs compared with the blank control and the nonpredator control. Web-building traits, however, were not significantly different between the blank control and the nonpredator control. One plausible explanation is that A. versicolor juveniles can detect and discriminate between predators and nonpredators through olfactory cues and alter stabilimentum building and other web traits in response to the risk of predation. This is the first demonstration of an adaptive, plastic web-building behavioural response induced by chemical cues from a predator. [Copyright &y& Elsevier]

Investigates the influence of optical cues on predatory behavior used by the jumping spider, Portia fimbriata in Australia. Cryptic stalking against standard virtual lure; Influence of the size of anterior median (AM) eyes on cryptic stalking; Freezing response when faced with lure with large AM eyes.

Portia is a genus of web-invading araneophagic jumping spiders known from earlier studies to derive aggressive-mimicry signals by using a generate-and-test algorithm (trial-and-error tactic). Here P. fimbriata's use of trial-and-error to solve a confinement problem (how to escape from an island surrounded by water) is investigated. Spiders choose between two potential escape tactics (leap or swim), one of which will fail (bring spider no closer to edge of tray) and the other of which will partially succeed (bring spider closer to edge of tray). The particular choice that will partially succeed is unknown to the spider. Using trial-anderror, P.fimbriata solves the confinement problem both when correct choices are rewarded (i.e. when the spider is moved closer to edge of tray) and when incorrect choices are punished (i.e. when the spider gets no closer to edge of tray). [ABSTRACT FROM AUTHOR]

Investigates the optical cues for prey discernment by the jumping spider Portia fimbriata. Adoption of ordinary stalking by P. fimbriata when lure did not have anterior-median eyes visible; Adoption of cryptic stalking only against intact lures on which the large anterior-median eyes are visible.

Examines scanning and route selection abilities of the jumping spider Portia labiata. Use of three different kinds of detours leading to a lure; Spider's choice of the complete route after visually inspecting two routes; Fixation on one route.

Examines the ability of Portia fimbriata from Queensland, Australia to choose between detour paths. Number of set-ups used in study; Types of detours; Frequency of correct route selection; Relationship between time of delay and route selection; Abandonment of wrong route detour.

The article focuses on the genus of spiders Portia's use of intellect to attack and capture other larger poisonous spiders as prey. It talks about the spiders planning before attacking a prey which helps it to sneak up on the prey. It tells about the spider using proto-counting due to which the spider is able to count his prey and plot a possible attack route. It speaks about the spider comparing the situations with the working memory of an attack.

The article focuses on the Portia fimbriata spider which belongs to the family Salticidae. The Portia is a carnivorous spider and it prefers to hunt jumping spiders which have four pairs of eyes with the large anterior median set the most obvious. It has several techniques that allow it to stalk larger spiders and it learns to detour if the prey cannot be easily approached. Once it gets close enough, it leaps, bites and injects a venom that will rapidly kill the prey.