Compound mimicry and trading predators by the males of sexually dimorphic Batesian mimics

Sexual dimorphism is pronounced in Myrmarachne, a large genus of ant-like jumping spiders (Salticidae) and one of the major animal groups in which Batesian mimicry of ants has evolved. Although adult females and juveniles of both sexes are distinctly ant-like in appearance, Myrmarachne males have elongated chelicerae that might appear to detract from their resemblance to ants. Experimental findings suggest that the Myrmarachne male's solution is to adopt compound mimicry (i.e. the male's model seems to be not simply an ant worker but a combination of an ant and something carried in the ant's mandibles: an "encumbered ant"). By becoming a mimic of a particular subset of worker ants, Myrmarachne males may have retained their Batesian-mimicry defence against ant-averse predators, but at the price of receiving the unwanted attention of predators for which encumbered ants are preferred prey. Two salticid species were used as predators in the experiments. Portia fimbriata is known to choose other salticids as preferred prey and to avoid unencumbered ants and their mimics (Myrmarachne females). In experiments reported here, P. fimbriata avoided encumbered ants and Myrmarachne males. Ants are the preferred prey of Chalcotropis gulosus. In our experiments, C. gulosus chose safer encumbered ants in preference to more dangerous unencumbered ants, chose Myrmarachne males more often than Myrmarachne females and showed no evidence of distinguishing between Myrmarachne males and encumbered ants. The cost of reconciling sexual dimorphism with Batesian mimicry appears to be that Myrmarachne males attract the unwanted attention of specialist predators of their compound model.     

The comparative study of the predatory behaviour of Myrmarachne, ant-like jumping spiders (Araneae: Salticidae)

The predatory behaviour of 31 species of Myrmarachne , ant-like salticids, was studied in the laboratory and the field. The ant-like morphology and locomotion of these spiders appears to function primarily in Batesian mimicry. No evidence was found of Myrmarachne feeding on ants. However, predatory sequences were found to differ considerably from those typical of salticids. Instead of stalking and leaping on prey, Myrmarachne lunged at prey from close range. Myrmarachne used its legs I to tap prey before lunging, another unusual behaviour for a salticid. Myrmarachne fed on a wide range of arthropod prey in nature and the laboratory, but appears to be especially efficient at catching moths. Also, Myrmarachne tends to open up, or enter into, other spiders' nests and eat other spiders' eggs. Myrmarachne males were less efficient than females, in laboratory tests, at catching various types of arthropod prey, but they appear to be as efficient as females at oophagy. Myrmarachne tend to use webs of other spiders as nest sites, but no evidence was found of Myrmarachne preying on spiders in webs. It appears that the unusual features of Myrmarachne's predatory and nesting behaviour are important in enabling these spiders to preserve their ant-like appearance.     

Vision-based innate aversion to ants and ant mimics

Innate vision-based aversions to model and mimic were investigatedusing a mimicry system in which the models were ants (Formicidae),and both the mimics and the predators were jumping spiders (Salticidae).Jumping spiders are a large group of predatory invertebratesthat usually prey opportunistically on prey of similar size.We used 12 representative species from this group, the "ordinarysalticids" as predators. The mimics considered belonged to anothergroup, salticids that resemble ants. A choice arena containingan empty chamber and a stimulus chamber was used for testingpredator responses to a variety of dead arthropods (ants, antmimics, and an array of non–ant-like species) mountedin a lifelike posture. When presented with visual cues fromarthropods other than ants or ant-like salticids, naive predatorschose the empty chamber no more often than the stimulus chamber.However, when visual cues were from ants or from ant-like salticids,ordinary salticids chose the empty chamber significantly moreoften than the stimulus chamber. These findings suggest learningby the predator is not necessary in order for ant-like salticidsto gain Batesian mimicry advantages.     

Prey classification by an araneophagic ant-like jumping spider (Araneae: Salticidae)

What to attack is one of the most basic decisions predators must make, and these decisions are reliant upon the predator's sensory and cognitive capacity. Active choice of spiders as preferred prey, or araneophagy, has evolved in several distantly related spider families, including jumping spiders (Salticidae), but has never been demonstrated in ant-like jumping spiders. We used prey-choice tests with motionless lures to investigate prey-choice behaviour in Myrmarachne melanotarsa , an East African ant-like salticid that normally lives in aggregations and often associates with other spider species. We show that M . melanotarsa chooses spiders as prey in preference to insects and, furthermore, discriminates between different types of spiders. Myrmarachne melanotarsa 's preferred prey were juvenile hersiliids and its second most preferred were other salticids. To date, all documented examples of araneophagic salticids have been from the basal subfamily Spartaeinae. Myrmarachne melanotarsa is the first non-spartaeine and also the first ant-like salticid for which araneophagy has been demonstrated.     

Out of the Frying Pan and into the Fire: a Novel Trade-Off for Batesian Mimics

A mimicry system was investigated in which the models were ants (Formicidae) and both the mimics and the predators were jumping spiders (Salticidae). By using motionless lures in simultaneous‐presentation prey‐choice tests, how the predators respond specifically to the static appearance of ants and ant mimics was determined. These findings suggest a rarely considered adaptive trade‐off for Batesian mimics of ants. Mimicry may be advantageous when it deceives ant‐averse potential predators, but disadvantageous in encounters with ant‐eating specialists. Nine myrmecophagic (ant‐eating) species (from Africa, Asia, Australia and North America) and one araneophagic (spider‐eating) species (Portia fimbriata from Queensland) were tested with ants (five species), with myrmecomorphic (ant‐like) salticids (six species of Myrmarachne) and with non‐ant‐like prey (dipterans and ordinary salticids). The araneophagic salticid chose an ordinary salticid and chose flies significantly more often than ants. Portia fimbriata also chose the ordinary salticid and chose flies significantly more often than myrmecomorphic salticids. However, there was no significant difference in how P. fimbriata responded to ants and to myrmecomorphic salticids. The myrmecophagic salticids chose ants and chose myrmecomorphic salticids significantly more often than ordinary salticids and significantly more often than flies, but myrmecophagic salticids did not respond significantly differently to myrmecomorphic salticids and ants.     

Innate aversion to ants (Hymenoptera: Formicidae) and ant mimics: experimental findings from mantises (Mantodea)

Field data suggest that ants may be important predators of mantises which, in turn, may be important predators of jumping spiders (Salticidae). Using a tropical fauna from the Philippines as a case study, the reactions of mantises to ants, myrmecomorphic salticids (i.e. jumping spiders that resemble ants) and ordinary salticids (i.e. jumping spiders that do not resemble ants) were investigated in the laboratory. Three mantis species ( Loxomantis sp., Orthodera sp., and Statilia sp.) were tested with ten ant species, five species of Myrmarachne (i.e. myrmecomorphic salticids), and 23 ordinary salticid species. Two categories of the myrmecomorphic salticids were recognized: (1) 'typical Myrmarachne ' (four species with a strong resemblance to ants) and (2) Myrmarachne bakeri (a species with less strong resemblance to ants). Ants readily killed mantises in the laboratory, confirming that, for the mantises studied, ants are dangerous. In alternate-day testing, the mantises routinely preyed on the ordinary salticids, but avoided ants. The mantises reacted to myrmecomorphic salticids similarly to how they reacted to ants (i.e. myrmecomorphic salticids appear to be, for mantises, Batesian mimics of ants). Although myrmecomorphic salticids were rarely eaten, M . bakeri was eaten more often than typical Myrmarachne . Because the mantises had no prior experience with ants, ant mimics or ordinary salticids, our findings suggest that mantises have an innate aversion to attacking ants and that this aversion is generalized to myrmecomorphic salticids even in the absence of prior experience with ants. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 88 , 23–32.     

Conditional use of honest signaling by a Batesian mimic

Jumping spiders (Salticidae) usually avoid ants, but some specieswithin this family single out ants as preferred prey, whileothers (especially the species in the genus Myrmarachne) areBatesian mimics of ants. Field records show that ant-eatingsalticids sometimes prey on Myrmarachne, suggesting that theunwanted attention of predators that specialize on the modelmay be an important, but poorly understood, cost of Batesianmimicry. By staging encounters in the laboratory between livingant-eating salticids and Myrmarachne, we determined that ant-eatingsalticids attack Myrmarachne. However, when Myrmarachne detectsa stalking ant-eating salticid early enough, it adopts a distinctivedisplay posture (legs almost fully extended, elevated 45°,and held out to the side 45°), and this usually deters thepredator. When Myrmarachne detects an ant-eating salticid beforestalking begins, Myrmarachne makes preemptive displays thatappear to inhibit the initiation of stalking. Using immobilelures made from dead Myrmarachne that were either in a displayposture or a nondisplay posture, we ascertained that specificallythe display posture of Myrmarachne deters the initiation ofstalking (ant-eating salticids stalked nondisplaying more oftenthan displaying lures). In another experiment, we ascertainedthat it is specifically the interjection of display posturethat deters stalking. When ant-eating salticids that had alreadybegun stalking experienced lures that switched from a nondisplayto a display posture, they stopped stalking. Although the unwantedattentions of its models' predators may be, for Myrmarachne,a hidden cost of Batesian mimicry, Myrmarachne appears to havean effective defense against these predators.     

Salticid predation as one potential driving force of ant mimicry in jumping spiders

Many spiders possess myrmecomorphy, and species of the jumping spider genus Myrmarachne exhibit nearly perfect ant mimicry. Most salticids are diurnal predators with unusually high visual acuity that prey on various arthropods, including conspecifics. In this study, we tested whether predation pressure from large jumping spiders is one possible driving force of perfect ant mimicry in jumping spiders. The results showed that small non-ant-mimicking jumping spiders were readily treated as prey by large ones (no matter whether heterospecific or conspecific) and suffered high attack and mortality rates. The size difference between small and large jumping spiders significantly affected the outcomes of predatory interactions between them: the smaller the juvenile jumping spiders, the higher the predation risk from large ones. The attack and mortality rates of ant-mimicking jumping spiders were significantly lower than those of non-ant-mimicking jumping spiders, indicating that a resemblance to ants could provide protection against salticid predation. However, results of multivariate behavioural analyses showed that the responses of large jumping spiders to ants and ant-mimicking salticids differed significantly. Results of this study indicate that predation pressure from large jumping spiders might be one selection force driving the evolution of nearly perfect myrmecomorphy in spiders and other arthropods.     

Dynamics of the evolution of Batesian mimicry: molecular phylogenetic analysis of ant-mimicking Myrmarachne (Araneae: Salticidae) species and their ant models

Batesian mimicry is seen as an example of evolution by natural selection, with predation as the main driving force. The mimic is under selective pressure to resemble its model, whereas it is disadvantageous for the model to be associated with the palatable mimic. In consequence one might expect there to be an evolutionary arms race, similar to the one involving host-parasite coevolution. In this study, the evolutionary dynamics of a Batesian mimicry system of model ants and ant-mimicking salticids is investigated by comparing the phylogenies of the two groups. Although Batesian mimics are expected to coevolve with their models, we found the phylogenetic patterns of the models and the mimics to be indicative of adaptive radiation by the mimic rather than co-speciation between the mimic and the model. This shows that there is strong selection pressure on Myrmarachne, leading to a high degree of polymorphism. There is also evidence of sympatric speciation in Myrmarachne, the reproductive isolation possibly driven by female mate choice in polymorphic species.     

Similar yet different: differential response of a praying mantis to ant‐mimicking spiders

Batesian mimics typically dupe visual predators by resembling noxious or deadly model species. Ants are unpalatable and dangerous to many arthropod taxa, and are popular invertebrate models in mimicry studies. Ant mimicry by spiders, especially jumping spiders, has been studied and researchers have examined whether visual predators can distinguish between the ant model, spider mimic and spider non‐mimics. Tropical habitats harbour a diverse community of ants, their mimics and predators. In one such tripartite mimicry system, we investigated the response of an invertebrate visual predator, the ant‐mimicking praying mantis (Euantissa pulchra), to two related ant‐mimicking spider prey of the genus Myrmarachne, each closely mimicking its model ant species. We found that weaver ants (Oecophylla smaragdina) were much more aggressive than carpenter ants (Camponotus sericeus) towards the mantis. Additionally, mantids exhibited the same aversive response towards ants and their mimics. More importantly, mantids approached carpenter ant‐mimicking spiders significantly more than often that they approached weaver ant‐mimicking spiders. Thus, in this study, we show that an invertebrate predator, the praying mantis, can indeed discriminate between two closely related mimetic prey. The exact mechanism of the discrimination remains to be tested, but it is likely to depend on the level of mimetic accuracy by the spiders and on the aggressiveness of the ant model organism.     

Observations in nature of detouring behaviour by Portia fimbriata, a web-invading aggressive mimic jumping spider from Queensland

Portia fimbriata , a web-invading, araneophagic salticid that uses aggressive mimicry to deceive its prey (web-building spiders), takes indirect routes to reach its prey (i.e. it makes detours). Data are presented from 18 instances of Portia making detours to reach prey in nature, the prey being five different species of web-building spiders. Portia spent 17 min (median) per predatory sequence with the prey out of view and covered 375 mm detouringper sequence. These detours were longer and more complex than those previously recorded for salticids, and these are the first detailed records of detouring behaviour by a salticid in the field.     

Mimicry complex in two central European zodariid spiders (Araneae: Zodariidae): how Zodarion deceives ants

Ant-eating spiders, Zodarion germanicum and Z. rubidum , were found to resemble ants structurally (size, colour, setosity) and behaviourally (ant-like movement, antennal illusion). Zodarion germanicum mimics large dark ants, such as Formica cinerea , whereas Z. rubidum resembles red ants, e.g. Myrmica sabuleti . Thus, these spiders are generalized Batesian mimics. The two spiders use aggressive mimicry during prey capture. When a spider carries a captured ant it will try to pass by approaching ants using special deceiving behaviour, which is based on imitation of ants' nestmate recognition. The spider first taps the antennae of the curious ant with its front legs (transmitting a tactile cue), then exposes its prey (the ant corpse) which the ant antennates (thus the corpse transmits an olfactory cue). The distal part of the front legs of Zodarion are almost without macrosetae similar to the antennae of ants. Additionally, all the other legs are covered with flattened incised setae, which imitate the dense setosity of ants' limbs. These remarkable microstructural imitations are believed to improve imitation of tactile signals by spiders. Moreover, by tapping, zodariids can presumably recognize the approaching intruder and decide whether to undertake the risk of deception or to run away. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 75 , 517–532.     

The biology of ant-like jumping spiders (Araneae, Salticidae): prey and predatory behaviour of Myrtnarachne with particular attention to M. lupata from Queensland

Myrtnarachne is a genus of ant-like salticids. Eight species were observed feeding, in nature, in Australia, Kenya, Malaysia and Sri Lanka, on varied types of insects but not ants. The behaviour of M. lupata , from Australia, was studied in the laboratory. Predatory sequences were found to differ considerably from those of typical salticids. Attacking by lunging instead of leaping and the pronounced use of pre-attack tapping are especially noteworthy. The unusual behaviour of M. lupata when preying on insects is consistent with maintenance of ant mimicry. Myrmarachne lupata also preys on the eggs of other spiders which it extracts from their nests. The males of many species have very large chelicerae, and the large chelicerae of M. lupata males influence the course of predatory sequences, with insects and with eggs.     

Alternative prey can change model–mimic dynamics between parasitism and mutualism

Classical (conventional) Müllerian mimicry theory predicts that two (or more) defended prey sharing the same signal always benefit each other despite the fact that one species can be more toxic than the other. The quasi‐Batesian (unconventional) mimicry theory, instead, predicts that the less defended partner of the mimetic relationship may act as a parasite of the signal, causing a fitness loss to the model. Here we clarify the conditions for parasitic or mutualistic relationships between aposematic prey, and build a model to examine the hypothesis that the availability of alternative prey is crucial to Müllerian and quasi‐Batesian mimicry. Our model is based on optimal behaviour of the predator. We ask if and when it is in the interest of the predator to learn to avoid certain species as prey when there is alternative (cryptic) prey available. Our model clearly shows that the role of alternative prey must be taken into consideration when studying model–mimic dynamics. When food is scarce it pays for the predator to test the models and mimics, whereas if food is abundant predators should leave the mimics and models untouched even if the mimics are quite edible. Dynamics of the mimicry tend to be classically Müllerian if mimics are well defended, while quasi‐Batesian dynamics are more likely when they are relatively edible. However, there is significant overlap: in extreme cases mimics can be harmful to models (a quasi‐Batesian case) even if the species are equally toxic. A crucial parameter explaining this overlap is the search efficiency with which indiscriminating vs. discriminating predators find cryptic prey. Quasi‐Batesian mimicry becomes much more likely if discrimination increases the efficiency with which the specialized predator finds cryptic prey, while the opposite case tends to predict Müllerian mimicry. Our model shows that both mutualistic and parasitic relationship between model and mimic are possible and the availability of alternative prey can easily alter this relationship.     

The natural history of Myrmarachne melanotarsa,a social ant‐mimicking jumping spider

Abstract

Myrmarachne melanotarsa, an ant‐like jumping spider (Salticidae) from East Africa, is an accurate mimic of Crematogaster sp. and associates unusually closely with its models. M. melanotarsa is remarkable in that it forms dense aggregations and builds large nest complexes (numerous individually‐occupied nests connected to each other by silk). Other salticids (Pseudicius spp., Menemerus spp.) live with M. melanotarsa in the same nest complex. These aggregations, which can exceed 50 conspecific individuals per colony, are considerably larger than those few previously described, and seem to have primarily a protective function. We provide baseline information on the natural history of M. melanotarsa, paying particular attention to predatory behaviour and association with Crematogaster sp., and fit this within current theory on the function of sociality in spiders. Other unusual behaviour of M. melanotarsa includes “mouthing”, in which the spider opens and closes its chelicerae while pressing its mouthparts against nest silk. We investigated the role of prior presence of Crematogaster sp. on nest silk in eliciting this previously unreported behaviour.     

Vision-based ability of an ant-mimicking jumping spider to discriminate between models,conspecific individuals and prey

Myrmarachne assimilis, an ant-like (myrmecomorphic) jumping spider (Araneae, Salticidae) from the Philippines, is a Batesian mimic of Oecophylla smaragdina, the Asian weaver ant. Salticids are well known for their acute eyesight and the elaborate vision-based display behaviour they adopt during encounters with conspecific individuals, but most salticids are not myrmecomorphic. Despite its unusual morphology, M. assimilis adopts display behaviour during intraspecific interactions that is similar to the display behaviour of more typical salticids. The specificity with which M. assimilis deploys display behaviour is investigated and provides insights into this mimic’s ability to differentiate, by sight alone, between models, conspecific individuals and prey. During each standardized test, an adult M. assimilis female was in a large cage along with a small transparent glass vial, a stimulus animal being enclosed in the vial such that potential optical cues, but not potential chemical cues, were available to the tested M. assimilis individual. Depending on the test, the stimulus animal was another adult M. assimilis female, a house fly (prey) or an ant (Camponotus sp. or O. smaragdina). Only the conspecific female consistently elicited display from M. assimilis, implying that M. assimilis is a Batesian mimic that can, when relying on vision alone, discriminate between conspecific individuals, models and prey. Received 12 June 2006; revised 22 September 2006; accepted 26 September 2006.     

Comparative biology of Portia africana,P. albimana,P. fimbriata,P. labiata,and P. shultzi,araneophagic, web-building jumping spiders (Araneae: Salticidae): Utilisation of webs,predatory versatility,and intraspecific interactions

Abstract

Portia is a behaviourally complex and aberrant salticid genus. The genus is of unusual importance because it is morphologically primitive. Five species were studied in nature (Australia, Kenya, Malaysia, Sri Lanka) and in the laboratory in an effort to clarify the origins of the salticids and of their unique, complex eyes. All the species of Portia studied were both web builders and cursorial. Portia was also an araneophagic web invader, and it was a highly effective predator on diverse types of alien webs. Portia was an aggressive mimic, using a complex repertoire of vibratory behaviour to deceive the host spiders on which it fed. The venom of Portia was unusually potent to other spiders; its easily autotomised legs may have helped Portia escape if attacked by its frequently dangerous prey. Portia was also kleptoparasitic and oophagic when occupying alien webs. P. fimbriata from Queensland, where cursorial salticids were superabundant, used a unique manner of stalking and capturing other salticids. The display repertoires used during intraspecific interactions were complex and varied between species. Both visual (typical of other salticids) and vibratory (typical of other web spiders) displays were used. Portia copulated both on and away from webs and frequently with the female hanging from a dragline. Males cohabited with subadult females on webs, mating after the female matured. Adult and subadult females sometimes used specialised predatory attacks against courting or mating males. Sperm induction in Portia was similar to that in other cursorial spiders. Portia mimicked detritus in shape and colour, and its slow, mechanical locomotion preserved concealment. Portia occasionally used a special defensive behaviour (wild leaping) if disturbed by a potential predator. Two types of webs were spun by all species (Type 1, small resting platforms; Type 2, large prey-capture webs). Two types of egg sacs were made, both of which were highly aberrant for a salticid. Responses of different species and both sexes of Portia were quantitatively compared for different types of prey. Many of the trends in behaviour within the genus, including quantitative differences in predatory behaviour, seemed to be related to differences in the effectiveness of the cryptic morphology of Portia in concealing the spider in its natural habitat (‘effective crypsis’). The results of the study supported, in general, Jackson & Blest’s (1982a) hypothesis of salticid evolution which, in part, proposes that salticid ancestors were web builders with poorly developed vision and that acute vision evolved in conjunction with the ancestral spiders becoming proficient as araneophagic invaders of diverse types of webs.     

Ant-mimicry in some Brazilian salticid and clubionid spiders (Araneae: Salticidae,Glubionidae)*

This paper describes the morphological and behavioural adaptations responsible for ant-like appearance in eight species (genera Zuniga, Synemosyna, Sphecotypus, and Myrmecium) of salticid and clubionid spiders studied in Amazonian and SE Brazil. All ant-mimicking spiders have body and legs thin, and the shiny integument typical of their models. Light horizontal hair bands and constrictions of the cephalothorax and abdomen simulate, respectively, the head-thorax joint and segmented gaster of ants. The petiole and postpetiole of the ants are usually mimicked by a lengthened pedicel, together with a narrowing of the posterior cephalothorax and/or anterior abdomen. The prominent pedipalps of the spiders often simulate ant mandibles, but they may also be strikingly similar to an ant's head. All ant-mimicking spiders walked in a zig-zag ant-like pattern, and frequently raised and moved about the first pair of legs as ‘antennae’. The mimics were found in the same microhabitats (foliage or ground) as their models, and displayed strong avoidance reactions toward the latter both in the field and in captivity. The inoffensive characteristics of the mimics and the noxious traits of their models (strong mandibles, potent sting, hard integument, venomous secretions) strongly suggest that the spiders are Batesian ant-mimics. The detailed structural and behavioural adaptations enhancing ant-mimicry provide strong circumstantial evidence that the selective agents involved must have good visual acuity, and are probably small insectivorous vertebrates (e.g. birds, lizards and toads) or arthropods (e.g. wasps and spiders) which avoid ants.     

The effect of alternative prey on the dynamics of imperfect Batesian and Müllerian mimicries

Both Batesian and Müllerian mimicries are considered classical evidence of natural selection where predation pressure has, at times, created a striking similarity between unrelated prey species. Batesian mimicry, in which palatable mimics resemble unpalatable aposematic species, is parasitic and only beneficial to the mimics. By contrast, in classical Müllerian mimicry the cost of predators' avoidance learning is shared between similar unpalatable co-mimics, and therefore mimicry benefits all parties. Recent studies using mathematical modeling have questioned the dynamics of Müllerian mimicry, suggesting that fitness benefits should be calculated in a way similar to Batesian mimicry; that is, according to the relative unpalatability difference between co-mimics. Batesian mimicry is very sensitive to the availability of alternative prey, but the effects of alternative prey for Müllerian dynamics are not known and experiments are rare. We designed two experiments to test the effect of alternative prey on imperfect Batesian and Müllerian mimicry complexes. When alternative prey were scarce, imperfect Batesian mimics were selected out from the population, but abundantly available alternative prey relaxed selection against imperfect mimics. Birds learned to avoid both Müllerian models and mimics irrespective of the availability of alternative prey. However, the rate of avoidance learning of models increased when alternative prey were abundant. This experiment suggests that the availability of alternative prey affects the dynamics of both Müllerian and Batesian mimicry, but in different ways.     

Ant mimicry lessens predation on a North American jumping spider by larger salticid spiders

Ant-like appearance (myrmecomorphy) has evolved >70 times in insects and spiders, accounting for >2,000 species of myrmecomorphic arthropods. Most myrmecomorphic spiders are considered to be Batesian mimics; that is, a palatable spider avoids predation through resemblance to an unpalatable ant-although this presumption has been tested in relatively few cases. Here we explicitly examined the extent to which Peckhamia picata (Salticidae), a North American ant-mimicking jumping spider, is protected from four species of jumping spider predators, relative to nonmimetic salticids and model ants. In addition, we conducted focused behavioral observations on one salticid predator, Thiodina puerpera, to determine the point at which the predators' behaviors toward model, mimic, and nonmimic diverge. We also examined the behaviors of Peckhamia in the presence of Thiodina. We found that mimetic jumping spiders were consumed less than a third as often as nonmimetic jumping spiders, suggesting that Peckhamia does indeed gain protection as a result of its resemblance to ants, and so can be considered a Batesian mimic. Furthermore, our focal predator did not consume any ant-mimicking spiders, and seemed to categorize Peckhamia with its model ant early in the hunting sequence. Such early determination of prey versus nonprey may be the result of speed-accuracy trade-offs in predator decision-making.