Florivorous myrmecophilous caterpillars exploit an ant–plant mutualism and distract ants from extrafloral nectaries

Females of myrmecophilous butterflies tend to oviposit in plants visited by ant species that engage in stable associations with its larvae. In Banisteriopsis malifolia, caterpillars are attended by the same ants that feed on extrafloral nectaries. A conflict may arise when both the plant and caterpillars compete for ant attention, and ants are assumed to forage on the highest quality resource. By attending caterpillars, ants can be indirectly detrimental to plant fitness because florivorous larvae feed intensively until pupation. In this study, we specifically investigated (i) whether the occurrence of facultative myrmecophilous Synargis calyce (Riodinidae) caterpillars in B. malifolia was based on ant species (Camponotus blandus or Ectatomma tuberculatum) and abundance; (ii) the monopolization of ants by the butterfly larvae and (iii) the florivory rates incurred by the caterpillars on inflorescences. The abundance of S. calyce was six‐fold greater in plants with C. blandus, compared to E. tuberculatum treatments. Caterpillars monopolized up to 50% of C. blandus on the plants, indicating that the resources offered by S. calyce were more attractive to ants than extrafloral nectaries. Florivory by riodinids incurred losses of almost 60% of flower buds. Myrmecophilous riodinids exploited an ant–plant mutualism by attracting aggressive ants that become larvae bodyguards. Thus, this ecological interaction is potentially detrimental to B. malifolia, since the ants, which can provide protection against herbivores, shift to provide defence for one of these herbivores.     

Ants,plant characteristics and habitat conservation status affect the occurrence of myrmecophilous butterflies on an extrafloral nectaried Malpighiaceae

We investigated the occurrence of myrmecophilous florivorous lycaenid larvae in Banisteriopsis malifolia (Malpighiaceae) according to habitat conservation status (disturbed and preserved savanna), plant phenology, height and the presence of tending ants. The abundance and richness of lycaenids were sixfold and fivefold greater, respectively, in the disturbed area than in the protected savanna. Lycaenids occurred mostly on plants visited by Camponotus blandus, a mutualistic partner of larvae. Habitat type was the main factor influencing lycaenid occurrence, as plants in open areas offered more food resources and tending ants. Banisteriopsis malifolia was considered useful as a host for lycaenids in disturbed sites.     

Adoption of lycaenid Niphanda fusca (Lepidoptera: Lycaenidae) caterpillars by the host ant Camponotus japonicus (Hymenoptera: Formicidae)

Caterpillars of the parasitic lycaenid butterfly are often adopted by host ants. It has been proposed that this adoption occurs because the caterpillars mimic the cuticular hydrocarbons of the host ant. This study aimed to examine whether caterpillars of the Japanese lycaenid butterfly Niphanda fusca induce adoption by mimicking their host ant Camponotus japonicus. Behavioral observations conducted in the laboratory showed that most second‐instar caterpillars were not adopted, whereas most third‐instar caterpillars were successfully adopted by host workers. A chemical comparison detected no characteristic differences in the cuticular hydrocarbon profiles between second‐ and third‐instar caterpillars. However, morphological features of the caterpillars differed between the second and third instars; third‐instar caterpillars developed exocrine glands (ant organs) such as tentacle organs and a dorsal nectary organ. These results suggest that multiple chemical signatures, not only cuticular hydrocarbons, may be important for invasion of the host ant nest.     

Associations between lycaenid butterflies and ants in Australia

A comprehensive and critical review of all available literature on associations between Australian lycaenid butterflies and ants was undertaken to establish an accurate database of the partners involved. Collections and observations of lycaenids and ants were used to augment this review, resulting in a significant number of newly documented association (and non-association) records. Twenty published records considered to be erroneous or doubtful are noted, with justifications given for their deletion from the association database. In total, 265 different associations between lycaenids and ants, plus 65 non-attendance records are documented for Australia. Nearly 80% of the lycaenid species in Australia, for which the early stages are known, are recorded associating with ants and half of these are obligately ant-associated. Patterns of association are examined from the perspective of both lycaenids and ants, with a focus on ant systematics and ecology. Lycaenids are recorded with five ant subfamilies, including the first record of an association with the Pseudomyrmecinae. The Dolichoderinae, and to some extent the Formicinae, have a disproportionately high percentage of genera that associate with lycaenid butterflies. All ant species that tend lycaenids spend at least some portion of their time foraging on vegetation to collect plant and insect nectar. There is a robust relationship between the competitive status of ants within a community, and their frequency and degree of association with lycaenids. Obligate ant-association is accompanied by a high degree of specificity for ant partner, but two notable exceptions, Ogyris aenone and O. amaryllis are discussed. Facultative myrmecophiles tend to associate with a broad range of ants, although interactions with ecologically dominant ants are less frequent than might be expected based on the abundance of dominant ant species in Australian communities.     

Timing of butterfly parasitization of a plant–ant–scale symbiosis

In the Southeast Asian tropics, Arhopala lycaenid butterflies feed on Macaranga ant-plants inhabited by Crematogaster (subgenus Decacrema) ants tending Coccus-scale insects. A recent phylogenetic study showed that (1) the plants and ants have been codiversifying for the past 20–16 million years (Myr), and that (2) the tripartite symbiosis was formed 9–7 Myr ago, when the scale insects became involved in the plant–ant mutualism. To determine when the lycaenids first parasitized the Macaranga tripartite symbiosis, we constructed a molecular phylogeny of the lycaenids that feed on Macaranga by using mitochondrial and nuclear DNA sequence data and estimated their divergence times based on the cytochrome oxidase I molecular clock. The minimum age of the lycaenids was estimated by the time-calibrated phylogeny to be 2.05 Myr, about one-tenth the age of the plant–ant association, suggesting that the lycaenids are latecomers that associated themselves with the pre-existing symbiosis of plant, ant, and scale insects.     

Behavioural ecology of defence in a risky environment: caterpillars versus ants in a Neotropical savanna

1. Predatory ants may reduce infestation by herbivorous insects, and slow‐moving Lepidopteran larvae are often vulnerable on foliage. We investigate whether caterpillars with morphological or behavioural defences have decreased risk of falling prey to ants, and if defence traits mediate host plant use in ant‐rich cerrado savanna. 2. Caterpillars were surveyed in four cerrado localities in southeast Brazil (70–460 km apart). The efficacy of caterpillar defensive traits against predation by two common ant species (Camponotus crassus, C. renggeri) was assessed through experimental trials using caterpillars of different species and captive ant colonies. 3. Although ant presence can reduce caterpillar infestation, the ants' predatory effects depend on caterpillar defence traits. Shelter construction and morphological defences can prevent ant attacks (primary defence), but once exposed or discovered by ants, caterpillars rely on their size and/or behaviour to survive (secondary defence). 4. Defence efficiency depends on ant identity: C. renggeri was more aggressive and lethal to caterpillars than C. crassus. Caterpillars without morphological defences or inside open shelters were found on plants with decreased ant numbers. No unsheltered caterpillar was found on plants with extrafloral nectaries (EFNs). Caterpillars using EFN‐bearing plants lived in closed shelters or presented morphological defences (hairs, spines), and were less frequently attacked by ants during trials. 5. The efficiency of defences against ants is thus crucial for caterpillar survival and determines host plant use by lepidopterans in cerrado. Our study highlights the effect of EFN‐mediated ant‐plant interactions on host plant use by insect herbivores, emphasizing the importance of a tritrophic viewpoint in risky environments.     

Elevated temperatures alter an ant‐aphid mutualism

Ant‐hemipteran mutualisms are keystone interactions that can be variously affected by warming: these mutualisms can be strengthened or weakened, or the species can transition to new mutualist partners. We examined the effects of elevated temperatures on an ant‐aphid mutualism in the subalpine zone of the Rocky Mountains in Colorado, USA. In this system, inflorescences of the host plant, Ligusticum porteri Coult. & Rose (Apiaceae), are colonized by the ant‐tended aphid Aphis asclepiadis Fitch or less frequently by the non‐ant tended aphid Cavariella aegopodii (Scopoli) (both Hemiptera: Aphididae). Using an 8‐year observational study, we tested for two key mechanisms by which ant‐hemipteran mutualisms may be altered by climate change: shifts in species identity and phenological mismatch. Whereas the aphid species colonizing the host plant is not changing in response to year‐to‐year variation in temperature, we found evidence that a phenological mismatch between ants and aphids could occur. In warmer years, colonization of host plant inflorescences by ants is decreased, whereas for A. asclepiadis aphids, host plant colonization is mostly responsive to date of snowmelt. We also experimentally established A. asclepiadis colonies on replicate host plants at ambient and elevated temperatures. Ant abundance did not differ between aphid colonies at ambient vs. elevated temperatures, but ants were less likely to engage in tending behaviors on aphid colonies at elevated temperatures. Sugar composition of aphid honeydew was also altered by experimental warming. Despite reduced tending by ants, aphid colonies at elevated temperatures had fewer intraguild predators. Altogether, our results suggest that higher temperatures may disrupt this ant‐aphid mutualism through both phenological mismatch and by altering benefits exchanged in the interaction.     

Ants benefit from attending facultatively myrmecophilous Lycaenidae caterpillars: evidence from a survival study

Workers of three ant species (Lasius niger, Lasius flavus, Myrmica rubra) were caged in the laboratory together with caterpillars and pupae of five species of lycaenid butterflies. Mortality of ants was 3–5 times higher when the ants were confined with larvae lacking a dorsal nectar organ (Lycaena phlaeas, Lycaena tityrus) rather than with caterpillars which possess a nectar gland (Aricia agestis, Polyommatus bellargus, P. icarus). For all five species, ant survival was always lower at the pupal stage (where a nectar organ is always absent) than at the caterpillar stage and was largely equivalent for the butterfly species tested. The experimental data confirm earlier estimates that ants can derive nutritive benefits from tending facultatively myrmecophilous lycaenid caterpillars, even though these caterpillars produce nectarlike secretions at low rates.     

Abiotic mediation of a mutualism drives herbivore abundance

Species abundance is typically determined by the abiotic environment, but the extent to which such effects occur through the mediation of biotic interactions, including mutualisms, is unknown. We explored how light environment (open meadow vs. shaded understory) mediates the abundance and ant tending of the aphid Aphis helianthi feeding on the herb Ligusticum porteri. Yearly surveys consistently found aphids to be more than 17‐fold more abundant on open meadow plants than on shaded understory plants. Manipulations demonstrated that this abundance pattern was not due to the direct effects of light environment on aphid performance, or indirectly through host plant quality or the effects of predators. Instead, open meadows had higher ant abundance and per capita rates of aphid tending and, accordingly, ants increased aphid population growth in meadow but not understory environments. The abiotic environment thus drives the abundance of this herbivore exclusively through the mediation of a protection mutualism.     

Mutualistic ants and parasitoid communities associated with a facultative myrmecophilous lycaenid,Arhopala japonica,and the effects of ant attendance on the avoidance of parasitism

Herbivorous insects have evolved various defensive strategies to avoid their primary enemies, parasitoids. Many species of Lycaenidae (Lepidoptera) have food‐for‐protection mutualism with ants in their larval stages, where larvae produce nectar for ants and in return ants exclude parasitoids as well as predators. Myrmecophilous relationships are divided into two categories, obligate and facultative, by degrees of myrmecophily. Although parasitoids attacking obligate lycaenids always encounter lycaenid‐specific ant species, parasitoids that use facultative lycaenids are likely to encounter diverse ant species showing various defense systems. However, we know little about the parasitoid community of facultative lycaenid larvae. In this study, we investigated the mutualistic ant and parasitoid communities of a facultative myrmecophilous species, Arhopala japonica, in seven localities in Japan. The present field observation newly recorded four ant species attending A. japonica larvae, and combined with the previous data, the number of attending ant species reached 16, which is nearly the maximum number of reported attending ant species among myrmecophilous lycaenids. However, the present study revealed that almost all parasitized A. japonica larvae were attacked by a single braconid species, Cotesia sp. near inducta. We also assessed the efficiency of facultative ant defense against the parasitoid in the laboratory and revealed that oviposition by Cotesia sp. near inducta females was almost completely hindered when A. japonica larvae were attended by ants. This suggests that the dominant parasitoid does not have effective traits to overcome defensive behavior of ants and that the female wasps oviposit mainly in A. japonica larvae without intensive attendance.     

Evolution of influence: signaling in a lycaenid-ant interaction

Some phytophagous insects gain defense from natural enemies by associating with otherwise potentially harmful top predators. Many lycaenid butterfly caterpillars are involved in such interactions with ants: larvae provide carbohydrate rewards from the dorsal nectary organ (DNO) to associated ants in return for protection from natural enemies. The stability of these interactions involves signals that identify the lycaenid caterpillar as a mutualist. However, larvae of some lycaenid species, such as Lycaena xanthoides, are found in close association with ants but do not possess the reward producing DNO. Evaluating the relationship in a phylogenetic framework, we show that the association between L. xanthoides and ants likely evolved from a non-ant-associated ancestor. Behavioral trials also show that L. xanthoides larvae are capable of influencing ant behavior to increase ant tending when faced with a simulated predator attack, without providing DNO-derived rewards to ant associates. These results demonstrate that the DNO is not necessary to maintain associations between lycaenid larvae and ants. Third-party interactions may affect the evolution of mutualisms and consideration of underlying evolutionary history is necessary to understand contemporary species associations.     

High invasive ant activity drives predation of a native butterfly larva

Yellow crazy ants (Anoplolepis gracilipes) threaten invertebrates on many tropical islands, but little work has been done in continental ecosystems. We found 4.4–16.0 times more cruiser butterfly caterpillars were attacked in Australian rain forest sites with A. gracilipes than in native ant sites, and extrafloral nectar had little influence.     

Bacterial communities within Phengaris (Maculinea) alcon caterpillars are shifted following transition from solitary living to social parasitism of Myrmica ant colonies

Bacterial symbionts are known to facilitate a wide range of physiological processes and ecological interactions for their hosts. In spite of this, caterpillars with highly diverse life histories appear to lack resident microbiota. Gut physiology, endogenous digestive enzymes, and limited social interactions may contribute to this pattern, but the consequences of shifts in social activity and diet on caterpillar microbiota are largely unknown. Phengaris alcon caterpillars undergo particularly dramatic social and dietary shifts when they parasitize Myrmica ant colonies, rapidly transitioning from solitary herbivory to ant tending (i.e., receiving protein‐rich regurgitations through trophallaxis). This unique life history provides a model for studying interactions between social living, diet, and caterpillar microbiota. Here, we characterized and compared bacterial communities within P. alcon caterpillars before and after their association with ants, using 16S rRNA amplicon sequencing and quantitative PCR. After being adopted by ants, bacterial communities within P. alcon caterpillars shifted substantially, with a significant increase in alpha diversity and greater consistency in bacterial community composition in terms of beta dissimilarity. We also characterized the bacterial communities within their host ants (Myrmica schencki), food plant (Gentiana cruciata), and soil from ant nest chambers. These data indicated that the aforementioned patterns were influenced by bacteria derived from caterpillars’ surrounding environments, rather than through transfers from ants. Thus, while bacterial communities are substantially reorganized over the life cycle of P. alcon caterpillars, it appears that they do not rely on transfers of bacteria from host ants to complete their development.     

Chemical disguise as particular caste of host ants in the ant inquiline parasite Niphanda fusca (Lepidoptera: Lycaenidae)

The exploitation of parental care is common in avian and insect 'cuckoos' and these species engage in a coevolutionary arms race. Caterpillars of the lycaenid butterfly Niphanda fusca develop as parasites inside the nests of host ants (Camponotus japonicus) where they grow by feeding on the worker trophallaxis. We hypothesized that N. fusca caterpillars chemically mimic host larvae, or some particular castes of the host ant, so that the caterpillars are accepted and cared for by the host workers. Behaviourally, it was observed that the host workers enthusiastically tended glass dummies coated with the cuticular chemicals of larvae or males and those of N. fusca caterpillars living together. Cuticular chemical analyses revealed that N. fusca caterpillars grown in a host ant nest acquired a colony-specific blend of cuticular hydrocarbons (CHCs). Furthermore, the CHC profiles of the N. fusca caterpillars were particularly close to those of the males rather than those of the host larvae and the others. We suggest that N. fusca caterpillars exploit worker care by matching their cuticular profile to that of the host males, since the males are fed by trophallaxis with workers in their natal nests for approximately ten months.     

Effects of an Epiphytic Orchid on Arboreal Ant Community Structure in Panama

Epiphytes are conspicuous structural elements of tropical forest canopies. Individual tree crowns in lowland forests may support more than 30 ant species, yet we know little about the effects of epiphytes on ant diversity. We examined the composition of arboreal ant communities on Annona glabra trees and their interactions with the epiphytic orchid Caularthron bilamellatum in Panama. We surveyed the ants on 73 trees (45 with C. bilamellatum and 28 lacking epiphytes) and recorded their nest sites and behavioral dominance at baits. We found a total of 49 ant species (in 20 genera), ranging 1–9 species per tree. Trees with C. bilamellatum had higher average (±SD) ant species richness (4.2±2.28) than trees without epiphytes (2.7±1.21). Hollow pseudobulbs (PBs) of C. bilamellatum were used as nest sites by 32 ant species, but only 43 percent of suitable PBs were occupied. Ant species richness increased with PB abundance in trees, but nest sites did not appear to be a limiting resource on A. glabra. We detected no close association between ants and the orchid. We conclude that higher ant species richness in the presence of the orchid is due to bottom‐up effects, especially the year‐round supply of extrafloral nectar. The structure of ant communities on A. glabra partly reflects interference competition among behaviorally dominant species and stochastic factors, as observed in other forests.     

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.     

Ant-partners play a minor role on occurrence of the myrmecophilous butterfly <Emphasis Type="Italic">Leptotes cassius</Emphasis> in its host plant

Ant-related oviposition in facultatively myrmecophilous lycaenid butterflies is common, but not universal. In fact, our knowledge of ant-related oviposition in lycaenids is based on some common species (e.g., Rekoa marius, Allosmaitia strophius, Parrhasius polibetes), which limits generalizations about these systems. In this study, we experimentally investigated whether the oviposition pattern of the florivorous lycaenid Leptotes cassius was influenced by the presence of Camponotus ants and whether larvae were attended, rather than attacked, by ants. This might be evidence of myrmecophily. Both L. cassius and Camponotus ants occur on Bionia coriacea, an extrafloral nectaried legume shrub that grows in the Brazilian cerrado. Plants were randomly assigned to ant-present and ant-excluded treatments and were observed twice throughout the short reproductive season. Larvae of L. cassius were tended by ants, whose attendance was characterized by active antennation on the last body segments of the caterpillars. Therefore, Camponotus can be considered a partner of L. cassius. Lycaenid abundance was on average 1.9- and 1.21-fold higher in plants with ants in each sampling period, respectively, indicating a tendency of L. cassius to occur in plants with ants. Nonetheless, results were not statistically significant, suggesting that in this case ants are not a major cue for lycaenid oviposition. In many ant–lycaenid mutualisms, butterfly immatures benefit from reduced parasitism rates. However, no L. cassius immature, regardless of ant presence or absence, was parasitized. Furthermore, larvae may occur inside flower buds that may provide protection from natural enemies; thus, ants may not be required for immature protection.     

Behavioral strategy of a lycaenid (Lepidoptera) caterpillar against aggressive ants in a Brazilian savanna

Myrmecophily is widespread in lycaenid butterflies, in which ants receive food resources and, in turn, protect caterpillars against natural enemies. This interaction ranges from obligate myrmecophily, in which immatures are invariably associated with ants and are dependent on ants for survival, and facultative myrmecophily, in which larvae are not dependent on ants for survival, but the presence of the latter may increase larvae survival. Lycaenids also include non-myrmecophilous butterflies, which do not have positive associations with ants and have developed strategies to avoid being attacked or preyed upon by them. In this study, we examined the relationship between the lycaenid Michaelus ira and two ant species associated with Distictella elongata (Bignoniaceae). This plant has extrafloral nectaries and is patrolled by Camponotus crassus and Ectatomma tuberculatum. Morphological analyses revealed that M. ira larvae have ant organs, such as dorsal nectary organs and perforated cupolas, structures associated with myrmecophily. We performed larval exposure experiments in the field, predicting that, in the absence of myrmecophily, the butterfly larva would present strategies to avoid ant attack. Results showed that larvae were attacked by both ant species. To escape ant molestation, larvae lived and fed inside silk-sealed D. elongata flower buds. We concluded that the M. ira bud-sheltering behavior was a defensive strategy against these ant species, while the dorsal nectary organs were apparently nonfunctional. Nonetheless, myrmecophily, in general, cannot be excluded in M. ira since relationships with other ant species may exist.     

Extrafloral‐nectaries and interspecific aggressiveness regulate day/night turnover of ant species foraging for nectar on Bionia coriacea

Plants bearing extrafloral nectaries (EFNs) vary the secretion of nectar between day and night, which creates turnover in the composition of interacting ant species. Daily variation in the composition of ant species foraging on vegetation is commonly observed, but its mechanisms are poorly understood. We evaluated the daily variation in nectar availability and interspecific aggressiveness between ants as possible regulatory mechanisms of the turnover in ant–plant interactions. We hypothesized that (i) plants would interact with more ant species during periods of higher secretion of nectar and that (ii) aggressive ant species would compete for nectar, creating a daily turnover of species collecting nectar. We tested this hypothesis by measuring the production of nectar during the day and night and by experimentally removing EFNs of Bionia coriacea (=Camptosema coriaceum) (Nees & Mart.) Benth. (Fabaceae: Faboideae) plants in a Brazilian savanna (Cerrado). We then compared the abundance and composition of ant species between those treatments and during the day. Our results indicate that more ant workers forage on plants during the day, when nectar was sugary, while more ant species forage at night, when aggressiveness between ant species was lower. We also detected a day/night turnover in ant species composition. Ant species foraging for nectar during the day were not the same at night, and this turnover did not occur on plants without EFNs. Both dominant ant species, diurnal Camponotus crassus (Hymenoptera: Formicidae) and nocturnal Camponotus rufipes (Hymenoptera: Formicidae), were the most aggressive species, attacking other ants in their specific periods of forage while also being very aggressive toward each other. However, this aggressiveness did not occur in the absence of nectar, which allowed non‐aggressive nocturnal ant species to forage only during the daytime, disrupting the turnover. We conclude that extrafloral‐nectar presence and interspecific aggressiveness between ants, along with other environmental factors, are important mechanisms creating turnovers in ants foraging on plants.