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.     

Garden ant homing behavior in a maze task based on local visual cues

Although it has been shown that visual cues play an essential role in navigation by the garden ant Lasius niger, no previous studies have addressed the way in which information from local visual cues is acquired and utilized in navigation. We found that in the absence of pheromone trails, ants whose homing motivation was triggered by feeding returned to the nest following local visual cues. In our experiments, the ants travelled through a maze to reach a feeder. They explored the maze and sometimes became trapped in its dead ends. We found that the ants more effectively used visual cues during their homeward journey if they experienced a dead end during their outward journey. This result suggested that the ants used the information acquired from visual cues during the outward journey to avoid a dead end on their return journey.     

An orb‐weaver spider eludes plant‐defending acacia ants by hiding in plain sight

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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.     

Myrmecophilous butterflies utilise ant–treehopper associations as visual cues for oviposition

1. Selection of a safe oviposition site is important for herbivorous insects whose immature stages have limited mobility. Female herbivores rely on environmental cues for this choice, and presence of natural enemies or mutualistic partners may be important in this process. 2. Some butterflies have mutualistic interactions with ants (myrmecophily), in which caterpillars offer a nutritional liquid and gain protection against natural enemies. Participants in butterfly–ant mutualisms may utilise signals to initiate interactions, but the use of visual cues by ovipositing myrmecophilous butterflies remains uncertain. 3. Larvae of facultatively myrmecophilous Parrhasius polibetes (Lycaenidae) feed on Schefflera vinosa, and females prefer to oviposit near aggregations of the ant‐tended treehopper Guayaquila xiphias, where caterpillars survive better due to increased ant attendance. Given the conspicuousness of ant–treehopper associations, it was investigated whether butterflies use them as visual cues for oviposition and, if so, which participants of the association are used as cues: ants, treehoppers, or both. 4. Experiments using dried insects on paired branches revealed that females visually recognise ants and ant–treehopper associations, using them for egg‐laying decisions. However, presence of a treehopper aggregation alone had no effect on oviposition choices. 5. This is a first insight into the importance of visual discrimination for ovipositing myrmecophilous butterflies. The results show that facultative mutualisms can be important enough to promote a behavioural adaptation (visual detection of ants) reinforcing the interaction. Our research highlights the importance of the behavioural interface within complex multispecies systems.     

Visual and Chemical Cues Used in Host Location and Acceptance by a Dipteran Parasitoid

Locating potential hosts for egg laying is a critical challenge in the life history of many insects. Female insects in several orders have evolved mechanisms to find hosts by using olfactory and visual signals derived from their hosts. We describe visual and chemical cues used by the dipteran parasitoid Apocephalus paraponerae (Diptera: Phoridae) in the location and acceptance of its host ant Paraponera clavata (Hymenoptera: Formicidae: Ponerinae). Our results show that A. paraponerae uses the visual cue of ant body size when locating hosts at short range and that these flies lay more eggs in ants that retain their surface chemicals than in ants with these chemicals removed. We compare the cues used by A. paraponerae with cues used by tephritid fruit flies in location and acceptance of their hosts, and we suggest further avenues for the study of host location, acceptance, and host discrimination of A. paraponerae and other parasitoids of ants.     

Extreme Reproduction and Survival of a True Cliffhanger: The Endangered Plant Borderea chouardii (Dioscoreaceae)

Cliff sides are extreme habitats, often sheltering a rich and unique flora. One example is the dioecious herb Borderea chouardii (Dioscoreaceae), which is a Tertiary, tropical relict, occurring only on two adjacent vertical cliffs in the world. We studied its reproductive biology, which in some aspects is extreme, especially the unusual double mutualistic role of ants as both pollinators and dispersers. We made a 2-year pollination census and four years of seed-dispersal experiments, recording flower visitors and dispersal rates. Fruit and seed set, self-sowing of seeds, seedling recruitment, and fate of seedlings from seeds sowed by different agents were scored over a period of 17 years. The ants Lasius grandis and L. cinereus were the main pollinators, whereas another ant Pheidole pallidula dispersed seeds. Thus ants functioned as double mutualists. Two thirds of all new seedlings came from self-sown seeds, and 1/3 was dispersed by ants, which gathered the seeds with their oil-rich elaiosome. Gravity played a minor role to dispersal. Both ant dispersal and self-sowing resulted in the same survival rate of seedlings. A double mutualism is a risky reproductive strategy, but B. chouardii buffers that by an unusual long–term demographic stability (some individuals exceed 300 years in lifespan) and its presence in a climatically very stable habitat, inaccessible to large herbivores. Such a combination of traits and habitat properties may explain the persistence of this relict species.     

Pre-adaptive shift of a native predator (Araneae, Zodariidae) to an abundant invasive ant species (Hymenoptera, Formicidae)

Invasive species often displace native species and can affect ecological processes in invaded habitats. If invasive species become abundant, changes in prey availability may be particularly harmful to specialist predators. The Argentine ant, Linepithema humile Mayr, is an important invasive species on nearly all continents. Spiders of the genus Zodarion are specialised ant-eating predators native to the Mediterranean yet it is unknown if they can exploit invasive ant species. Here we studied spatial and temporal abundance of this invasive ant and the native spider, Zodarion cesari Pekár, during 4?years in four citrus groves. Circadian activity of both spiders and ants, and capture efficiency and prey specificity of the predator were also evaluated. The abundance of Z. cesari was strongly correlated to L. humile abundance. The predatory activity of spiders varied seasonally with differences on the relative frequency of spiders capturing ants depending on the time of the year. In laboratory, Z. cesari displayed most efficient capture upon the native ant Tapinoma nigerrimum (Nylander) and the invasive ant L. humile in comparison with five other native ant species. These results demonstrate that the native spider Z. cesari is successfully exploiting the invasive ant species L. humile and is likely a locally monophagous predator. We suggest that Z. cesari shifted away from native T. nigerrimum post invasion as both ant species are phylogenetically related and of similar size.     

Poor Display Repertoire, Tolerance and Kleptobiosis: Results of Specialization in an Ant-Eating Spider (Araneae, Zodariidae)

The agonistic display repertoire of myrmecophagous Zodarion rubidum has five displays. This is fewer than in other spiders, which is a result of the short time spent in contests (4 s). Such a short duration seems to be an adaptation to living among foraging ants, which are dangerous to spiders. The interaction procedure was markedly affected by the presence of preyimmobilized ant. Contests between individuals without prey, or each holding prey, were usually resolved by leg waving. But contests between an individual without and an individual with prey escalated to more aggressive levels. Nevertheless, spiders were never observed to harm or cannibalize one another. Absence of cannibalism is explained as a result of diet specialization: only ants elicit a predatory behavior and provide Zodarion spiders with optimal nutrients. Some spiders used kleptobiosis to gain ants. They first tried to gain immobilized prey aggressively and if failed they adopted a stealthy tactic and shared the prey with the owner. Kleptobiosis is an alternative foraging strategy for Zodarion spiders as it reduces risks associated with hunting dangerous ants.     

Compound Eye Adaptations for Diurnal and Nocturnal Lifestyle in the Intertidal Ant,Polyrhachis sokolova

The Australian intertidal ant, Polyrhachis sokolova lives in mudflat habitats and nests at the base of mangroves. They are solitary foraging ants that rely on visual cues. The ants are active during low tides at both day and night and thus experience a wide range of light intensities. We here ask the extent to which the compound eyes of P. sokolova reflect the fact that they operate during both day and night. The ants have typical apposition compound eyes with 596 ommatidia per eye and an interommatidial angle of 6.0°. We find the ants have developed large lenses (33 µm in diameter) and wide rhabdoms (5 µm in diameter) to make their eyes highly sensitive to low light conditions. To be active at bright light conditions, the ants have developed an extreme pupillary mechanism during which the primary pigment cells constrict the crystalline cone to form a narrow tract of 0.5 µm wide and 16 µm long. This pupillary mechanism protects the photoreceptors from bright light, making the eyes less sensitive during the day. The dorsal rim area of their compound eye has specialised photoreceptors that could aid in detecting the orientation of the pattern of polarised skylight, which would assist the animals to determine compass directions required while navigating between nest and food sources.     

Visual Navigation during Colony Emigration by the Ant Temnothorax rugatulus

Many ants rely on both visual cues and self-generated chemical signals for navigation, but their relative importance varies across species and context. We evaluated the roles of both modalities during colony emigration by Temnothorax rugatulus. Colonies were induced to move from an old nest in the center of an arena to a new nest at the arena edge. In the midst of the emigration the arena floor was rotated 60°around the old nest entrance, thus displacing any substrate-bound odor cues while leaving visual cues unchanged. This manipulation had no effect on orientation, suggesting little influence of substrate cues on navigation. When this rotation was accompanied by the blocking of most visual cues, the ants became highly disoriented, suggesting that they did not fall back on substrate cues even when deprived of visual information. Finally, when the substrate was left in place but the visual surround was rotated, the ants'' subsequent headings were strongly rotated in the same direction, showing a clear role for visual navigation. Combined with earlier studies, these results suggest that chemical signals deposited by Temnothorax ants serve more for marking of familiar territory than for orientation. The ants instead navigate visually, showing the importance of this modality even for species with small eyes and coarse visual acuity.     

Negative effects of ant foraging on spiders in Douglas-fir canopies

 Spiders and ants are potential competitors and mutual predators. Indirect evidence from previous research has suggested that ant foraging may significantly lower the abundance of arboreal spiders in young Douglas-fir plantations in western Oregon. This study tested the effect of foraging by ants, dominated by Camponotus spp., on spider assemblages in Douglas-fir canopies in a 5-month ant-exclusion experiment. The biomass of potential prey organisms on foliage, dominated by Psocoptera, increased significantly by 1.9- to 2.4-fold following ant exclusion. The removal of ants did not affect the abundance of flying arthropods in the vicinity of tree canopies as indicated by sticky trap catches. The abundance of hunting spiders, the majority being Salticidae, increased significantly by 1.5- to 1.8-fold in trees without ants in the late summer; neither the abundance of web-building spiders nor the average body size of hunting and web-building spiders were significantly affected by ant removal. Spider diversity and community structure did not differ significantly between control and ant-removal trees. The majority of prey captured by ants were Aphidoidea (48.1%) and Psocoptera (12.5%); spiders represented only 1.4% of the ants’ diet. About 40% of observed ants were tending Cinara spp. aphids. Our observations suggest that the lower abundance of hunting spiders in control canopies with ants may be due to interference competition with ants resulting from ant foraging and aphid-tending activities. Direct predation of spiders by ants appeared to be of minor importance in this study system. This study did not provide sufficient evidence for exploitative competition for prey between ants and spiders. Received: 21 February 1996 / Accepted: 14 August 1996     

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.     

Are ants botanists? Ant associative learning of plant chemicals mediates foraging for carbohydrates

1. Although associative learning is widespread across animals, its ecological importance is difficult to assess because learning is rarely studied in the field, where informative cues are juxtaposed against complex backgrounds of uninformative noise. 2. Ants rely heavily on chemical cues for foraging and engage in many ecologically important interactions with plants. Nevertheless, little is known about the role of associative learning of plant chemicals in ant foraging for carbohydrates. 3. In a field setting, the present study investigated whether the distantly related ant species Formica podzolica (Formicinae subfamily) and Tapinoma sessile (Dolichoderinae subfamily) exhibited associative learning of the chemical cues from two co-occurring plant species that are taxonomically and chemically distinct (Asteraceae: Helianthella quinquenervis and Apiaceae: Ligusticum porteri). 4. For two consecutive summers, ants were trained to forage from artificial sugar-rich baits associated with the leaf chemicals from either H. quinquenervis or L. porteri for 24 h, after which a two-choice test was deployed to assess whether ants would be more likely to select baits associated with the same (versus different) plant chemicals on which they had been trained. 5. The present study demonstrates associative learning of chemicals from both plant species, and these effects were consistent between ant species and years; training increased bait occupancy from 42% on the untrained scent to 66% on the trained scent. These results indicate that associative odour-learning may be widespread across ants and serve as an important mechanism mediating ant selection of resources.     

Ant–hemipteran association decreases parasitism of Phenacoccus solenopsis by endoparasitoid Aenasius bambawalei

1. Mutualism between ants and honeydew-excreting hemipterans is ubiquitous in the ecosystem. It is widely accepted that ant tending facilitates the colony growth of hemipterans by protecting them from predators and parasitoids. However, few studies have explored how ant tending helps defend against natural enemies. 2. Ghost ant Tapinoma melanocephalum and the invasive mealybug Phenacoccus solenopsis have a close mutual relationship. Previous studies have shown that ghost ant tending can definitely reduce parasitism and visit frequency of Aenasius bambawalei, the dominant endoparasitoid of P. solenopsis. However, the ghost ant workers seldom attack the parasitoids. It is still unclear how the ghost ant adversely affects parasitoids. This study explored the mechanism underlying the impacts of ants on natural enemies of the mealybugs. 3. Honeydew produced by P. solenopsis was an attractant to A. bambawalei. Parasitoids exhibited less searching activity, shorter longevity and lower parasitism when supplied with less honeydew. Aenasius bambawalei showed significant avoidance of pygidial gland secretions and visual cues of ghost ants. Parasitism in plants treated with 6-methyl-5-hepten-2-one, actinidine, and gland extracts was significantly lower than that in plants treated only with solvents (paraffin oil or double-distilled water). 4. It is concluded that honeydew consumption by ghost ants could negatively influence the performance of parasitoids. The pygidial gland secretions and visual cues of ghost ants also significantly inhibit the parasitism. These results may contribute to a better understanding of the regulation mechanism in ant–hemipteran–enemy interactions.     

Plant choice,herbivory and weight gain of wood crickets under the risk of predation

Predators can indirectly reduce herbivory by killing herbivores. In addition, predation risk can influence the feeding rate and feeding location of herbivores. Herbivores are expected to avoid plants currently occupied by a predator. Consequently, less herbivory is expected on plants bearing fresh predator cues. We examined whether wood crickets, Nemobius sylvestris Bosc (Orthoptera: Gryllidae), avoided plants bearing the chemical cues of nursery web spiders, Pisaura mirabilis Clerck (Araneae: Pisauridae), or red wood ants, Formica rufa L. (Hymenoptera: Formicidae). We conducted a series of behavioural experiments, in which crickets had the choice between a plant with spider or ant cues vs. a control plant, a plant with spider cues vs. a plant with ant cues, or two control plants. For all plants, we quantified leaf damage and the position and weight change in the crickets. Crickets avoided plants with spider cues. In contrast, ant cues did not significantly deter crickets. The herbivory pattern among the plants reflected the plant choice of the crickets. However, net herbivory was not affected by the presence of predator cues. Thus, our results suggest that spider cues affect feeding location rather than the total amount of herbivory.     

Mimetic host shifts in an endangered social parasite of ants

An emerging problem in conservation is whether listed morpho-species with broad distributions, yet specialized lifestyles, consist of more than one cryptic species or functionally distinct forms that have different ecological requirements. We describe extreme regional divergence within an iconic endangered butterfly, whose socially parasitic young stages use non-visual, non-tactile cues to infiltrate and supplant the brood in ant societies. Although indistinguishable morphologically or when using current mitochondrial and nuclear sequence-, or microsatellite data, Maculinea rebeli from Spain and southeast Poland exploit different Myrmica ant species and experience 100 per cent mortality with each other''s hosts. This reflects major differences in the hydrocarbons synthesized from each region by the larvae, which so closely mimic the recognition profiles of their respective hosts that nurse ants afford each parasite a social status above that of their own kin larvae. The two host ants occupy separate niches within grassland; thus, conservation management must differ in each region. Similar cryptic differentiation may be common, yet equally hard to detect, among the approximately 10 000 unstudied morpho-species of social parasite that are estimated to exist, many of which are Red Data Book listed.     

A castration parasite of an ant-plant mutualism

Exploring the factors governing the maintenance and breakdown of cooperation between mutualists is an intriguing and enduring problem for evolutionary ecology, and symbioses between ants and plants can provide useful experimental models for such studies. Hundreds of tropical plant species have evolved structures to house and feed ants, and these ant–plant symbioses have long been considered classic examples of mutualism. Here, we report that the primary ant symbiont, Allomerus cf. demerarae, of the most abundant ant-plant found in south-east Peru, Cordia nodosa Lam., castrates its host plant. Allomerus workers protect new leaves and their associated domatia from herbivory, but destroy flowers, reducing fruit production to zero in most host plants. Castrated plants occupied by Allomerus provide more domatia for their associated ants than plants occupied by three species of Azteca ants that do not castrate their hosts. Allomerus colonies in larger plants have higher fecundity. As a consequence, Allomerus appears to benefit from its castration behaviour, to the detriment of C. nodosa. The C. nodosa–ant system exhibits none of the retaliatory or filtering mechanisms shown to stabilize cheating in other cooperative systems, and appears to persist because some of the plants, albeit a small minority, are inhabited by the three species of truly mutualistic Azteca ants.     

Recognition in a Social Symbiosis: Chemical Phenotypes and Nestmate Recognition Behaviors of Neotropical Parabiotic Ants

Social organisms rank among the most abundant and ecologically dominant species on Earth, in part due to exclusive recognition systems that allow cooperators to be distinguished from exploiters. Exploiters, such as social parasites, manipulate their hosts’ recognition systems, whereas cooperators are expected to minimize interference with their partner’s recognition abilities. Despite our wealth of knowledge about recognition in single-species social nests, less is known of the recognition systems in multi-species nests, particularly involving cooperators. One uncommon type of nesting symbiosis, called parabiosis, involves two species of ants sharing a nest and foraging trails in ostensible cooperation. Here, we investigated recognition cues (cuticular hydrocarbons) and recognition behaviors in the parabiotic mixed-species ant nests of Camponotus femoratus and Crematogaster levior in North-Eastern Amazonia. We found two sympatric, cryptic Cr. levior chemotypes in the population, with one type in each parabiotic colony. Although they share a nest, very few hydrocarbons were shared between Ca. femoratus and either Cr. levior chemotype. The Ca. femoratus hydrocarbons were also unusually long–chained branched alkenes and dienes, compounds not commonly found amongst ants. Despite minimal overlap in hydrocarbon profile, there was evidence of potential interspecific nestmate recognition –Cr. levior ants were more aggressive toward Ca. femoratus non-nestmates than Ca. femoratus nestmates. In contrast to the prediction that sharing a nest could weaken conspecific recognition, each parabiotic species also maintains its own aggressive recognition behaviors to exclude conspecific non-nestmates. This suggests that, despite cohabitation, parabiotic ants maintain their own species-specific colony odors and recognition mechanisms. It is possible that such social symbioses are enabled by the two species each using their own separate recognition cues, and that interspecific nestmate recognition may enable this multi-species cooperative nesting.     

Memory and chemical communication in the orientation of two mass-recruiting ant species

Summary The relative contribution of visual and chemical components in the orientation ofLasius niger andIridomyrmex humilis (Argentine ant) workers during mass recruitment to newly discovered food sources is analyzed over short time intervals. While both species orient in response to the trail pheromone, a large number ofL. niger foragers rapidly switch to a more individual orientation, based on their memory of environmental cues.I. humilis workers, on the other hand, predominantly use collective chemical cues. The effect of the number of reinforcements on visual learning and its interference with chemical communication show that olfactory cues always prevail in the Argentine ant. InL. niger, the proportion of ants orienting to visual cues is independent of the trail concentration. Detailed observations of the trail-laying behavior of individually marked foragers show that nearly all theI. humilis workers initially lay a trail, whereas only half theL. niger foragers do so. This proportion decreases considerably with the number of trips performed byL. niger workers, while remaining constant for the Argentine ants. These results are interpreted with respect to the species' behavioral ecology.