Lycaenid Larvae Research Articles

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

AbstractHerbivorous 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.

Absence of cuticular alkenes allows lycaenid larvae to avoid predation by Formica japonica ants

AbstractChemical mimicry and camouflage based on cuticular hydrocarbons (CHCs) are adaptive strategies that are frequently observed in myrmecophilous insects. The larvae of several lycaenid butterfly species that exhibit obligate associations with specific ant species have been reported to use chemical mimicry. However, little is known about the strategies used by the larvae of species that have facultative associations with multiple ant species. We attempted to reveal the effects of larval CHC profiles on interactions with Formica japonica workers, using three lycaenid species, two facultative ant‐associated (Lycaeides argyrognomon and Zizeeria maha) and one non‐ant‐associated (Lycaena phlaeas), which commonly possess n‐alkanes as the major CHCs. In field bioassays, the lycaenid larvae were attacked by ant workers less often than larvae of Papilio polytes (Papilionidae), the CHCs of which were rich in 7‐alkenes. Treating the lycaenid larvae with 7‐heptacosene and 9‐heptacosene significantly activated ant aggression (biting), whereas treating them with n‐heptacosane, n‐octacosane and 13‐methylheptacosane had little effect. Furthermore, larvae of Pieris rapae (Pieridae), possessing n‐alkanes as the dominant CHCs, suffered an intermediate level of ant biting between the lycaenid and Pa. polytes larvae. However, treatments of the P. rapae larvae with 7‐heptacosene and 9‐heptacosene significantly affected the frequency of ant biting. These findings suggest that the absence of alkenes in larval CHC profiles is an effective means of circumventing predation by ants and allows lycaenid larvae to inhabit the foraging territory of predaceous ants, at least to some extent.

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

ABSTRACTWe 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.

The setae of parasiticLiphyra brassolisbutterfly larvae form a flexible armour for resisting attack by their ant hosts (Lycaenidae: Lepidoptera)

Caterpillars of the lycaenid butterfly, Liphyra brassolis, live inside the nests of arboreal weaver ants, Oecophylla smaragdina, and eat their brood. Observations of mature larvae suggest that they are impervious to relentless ant molestation, yet they lack sclerotized cuticular plates. We document a novel form of integumental defence that imparts protection from ant attack whilst maintaining the flexibility necessary to walk with a hydraulic skeleton. Analysis of the trunk integument and cuticular structures of early and late instars of L. brassolis using light microscopy, scanning electron microscopy, and histology revealed three new setae types (disc, clavate, and lanceolate), as well as three new cuticular structures (pored sockets, cuticular pores, and cuticular domes). The unique cuticle is covered with lanceolate setae, which act as endocuticular struts, and overlapping scale-like sockets, which form a hard, flexible integument. The imperfect armour of the early-instar larvae suggests that abundant, putatively secretory pores are likely to be homologous to pore cupola organs (PCOs) found in other lycaenid larvae and thus may exude semiochemicals to allay ant aggression. The importance of these pores presumably wanes as structural (setal) cuticular defenses are reinforced in later instars, when adult ants have been observed attacking caterpillars to no avail. The caterpillar's antennae are unusual and seem to be involved in manipulating ant larvae into the caterpillar's mouth. Behavioural observations indicate that the dexterity of these structures is associated with eating ants (myrmecophagy).

Myrmecoxeny inArhopala zylda(Lepidoptera, Lycaenidae) Larvae Feeding onMacarangaMyrmecophytes

ABSTRACT Some species in the tree genus Macaranga (Euphorbiaceae) in the Southeast Asian tropics are myrmecophytic; they have highly species-specific mutualisms with symbiotic ants (plant-ants), which defend them from herbivores. However, larvae of some Arhopala (Lycaenidae, Lycaeninae) species can elude the ants. Here we demonstrated that Arhopala zylda larvae showed myrmecoxeny on their myrmecophytic Macaranga host plants; they had no stable association with the plant-ants. Despite the presence of many plant-ants, A. zylda larvae were rarely attended or attacked by ants on their host plants. The plant-ants of three other myrmecophytic Macaranga species (non-hosts to A. zylda) also paid little attention to experimentally introduced A. zylda larvae. The myrmecoxeny seen in A. zylda is notable among lycaenid larvae that feed on myrmecophytes, because almost all are obligate intimate myrmecophiles.

Absence of pollinators and apomictic fruit production in an Atlantic rainforest population of Cymbopetalum brasiliense (Annonaceae)

Breeding system and pollination biology of an isolated population of Cymbopetalum brasiliense (Annonaceae), a large-flowered understory tree, was studied during two consecutive flowering seasons in October/November 2007 and September/October 2008. Flowers were morphologically comparable to other Cymbopetalum species and generally to other Annonaceae taxa adapted to pollination by large beetles, such as Annona spp. Flowers were thermogenic and emitted a strong scent during the pistillate and staminate flowering phases. Heating of the floral chamber was most intense during the pistillate phase between 1800 and 1900 h (up to 6°C difference to air temperature). Floral scent consisted almost entirely of p-methylanisole. None of the 133 flowers examined during two seasons received any visitation by dynastid beetles or other potential pollinators. Lycaenid larvae (Oenomaus ortygnus) attacked buds and flowers in both flowering seasons and destroyed about 20% of all buds in the 2007 season. Fruit set was high (72% of nonpredated flowers in 2007), despite the absence of pollinators. Field experiments showed that agamospermic reproduction rather than self-pollination was most likely responsible for fruit production. The study reports a probable case of apomixis, which would be the first in the Annonaceae family.

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.

Differences in the behaviour of ants towards two larval instars of Lycaena tityrus (Lep., Lycaenidae)

Tetramorium caespitum workers exhibit much more typical symphilic behaviour towards 4th instar larvae of Lycaena tityrus than towards the previous instars. The intensity of this behaviour of ants is much lower towards these myrmecoxenous lycaenid caterpillars than towards myrmecophilous larvae, e.g. Polyommatus coridon. The pore cupola organs are most likely the organs releasing the palpation behaviour of the ants. The larval strategies of myrmecoxenous (avoidance of ant aggressiveness) and myrmecophilous (mutualistic symbioses with ants) lycaenid larvae are compared.

Differences in worker caste behaviour of Oecophylla smaragdina (Hymenoptera: Formicidae) in response to larvae of Anthene emolus (Lepidoptera: Lycaenidae)

The larvae of Anthene emolus (Lycaenidae) cannot survive in the wild without their associated ant Oecophylla smaragdina (Formicidae). The ants groom the lycaenid larvae for secretions and, in turn, protect them from parasitoids and predators. Both major and minor worker ants tend larvae, although, in the present study, the frequencies of tending by different castes proved to be significantly different. Ants also tended late instars significantly more than young larvae. O. smaragdina ants of the same colony were observed fighting when A. emolus larvae were present. Aggression was exhibited by the major workers against the minor workers that tried to tend secreting larvae. Major ants precluded the minors from the most nutritious secretions, leaving minors to tend the less productive, early instars. On a few occasions, aggression was unchecked and major workers killed the larvae they were tending (presumably accidentally). When larvae were experimentally reared with only one caste of ant, the resulting butterflies showed no differences in dry weight. Mortality was high when larvae were reared with only minor ants or in the absence of ants.

The ecology and evolution of ant association in the Lycaenidae (Lepidoptera).

The estimated 6000 species of Lycaenidae account for about one third of all Papilionoidea. The majority of lycaenids have associations with ants that can be facultative or obligate and range from mutualism to parasitism. Lycaenid larvae and pupae employ complex chemical and acoustical signals to manipulate ants. Cost/benefit analyses have demonstrated multiple trade-offs involved in myrmecophily. Both demographic and phylogenetic evidence indicate that ant association has shaped the evolution of obligately associated groups. Parasitism typically arises from mutualism with ants, and entomophagous species are disproportionately common in the Lycaenidae compared with other Lepidoptera. Obligate associations are more common in the Southern Hemisphere, in part because highly ant-associated lineages make up a larger proportion of the fauna in these regions. Further research on phylogeny and natural history, particularly of the Neotropical fauna, will be necessary to understand the role ant association has played in the evolution of the Lycaenidae.

Induced indirect defence in a lycaenid-ant association: the regulation of a resource in a mutualism.

Indirect defences involve the protection of a host organism by a mutualistic partner. Threat of predation to the host organism may induce the production of rewards and/or signals that attract the mutualistic partner. In laboratory and field experiments we show that threatened lycaenid butterfly larvae (Plebejus acmon) produce more nectar rewards from their gland and were tended by protective ants twice as much as controls. Ant attendance did not affect the leaf consumption or feeding behaviour of larvae in the absence of predators. Inducible nectar production and indirect defence in this system may be a mechanism by which larvae provide rewards for services when they are needed the most. Such a system may stabilize the mutualistic association between lycaenid larvae and ants by preventing exploitation by either partner.

Variation in behavior of lycaenid larvae when attended by different ant species

Partner quality can be crucial for the outcome of a mutualistic interaction. In multi-species associations, the characteristics of potential partners can vary substantially and thus the associated benefits. As a consequence of such variation, one might expect strategies of adjusting investments to the characteristics of a partner. Lycaenid butterfly larvae often interact mutualistically with several ant species of different size and aggressiveness and thereby different ability to protect the larvae. Attending ants are rewarded with nutritious secretions. Both ant behavior and a larva's need for protection are known to influence larval investment in the relationship. This study investigates the effect of six ant species on larval behavior in the lycaenid butterfly, Glaucopsyche lygdamus. The overall level of secretion, as well as the response to varying number of attending ants, were found to be influenced by ant species.

REVIEW: Lycaenid-ant interactions of the Maculinea type: tracing their historical roots in a comparative framework

Parasitic relationships between lycaenid butterfly larvae and ants are contrasted with the more common, and ancestral, mutualistic butterfly-ant associations. Three types of lycaenid-ant parasitism can be recognized: (i) the Miletinae type (derived from predation on Homoptera); (ii) the Aphnaeini type (derived from obligate and specific mutualism or commensalism); and (iii) the Maculinea type (derived from facultative mutualism, only represented by the genera Maculinea and Lepidochrysops). Parasitic lycaenid-ant interactions are rare (37 confirmed recorded cases worldwide) and are mostly confined to single species, or small species-groups, in larger non-parasitic clades. Only the two genera representing the Maculinea type have undergone substantial radiation. Ant-parasitic lycaenids predominantly occur in highly seasonal habitats with an extended unfavourable dry or cold season. These observations suggest that (a) parasitic interactions are relatively unstable in evolutionary time, and (b) their evolution usually started with caterpillars seeking shelter in ant nests. Ecological and zoogeographical data for species of the Glaucopsychiti (of which Maculinea forms a part) are compiled and used to discuss the evolutionary origin of ant-parasitism in Maculinea butterflies in a comparative framework. These comparisons suggest that (a) Maculinea evolved from facultative unspecific ant-mutualists, (b) the loss of larval tentacle organs is primarily related to their endophytic feeding habits, (c) that Lamiaceae were the hostplants of ancestral Maculinea, and (d) that Maculinea evolved in eastern central Asia. Further phylogenetic and biogeographical analyses are required to quantitatively test these possibilities. © Rapid Science Ltd. 1998

Aggregation as a cost-reducing strategy for lycaenid larvae

If a mutualistic relationship entails providing services at a cost, selection will favor individuals that maximize the net benefits of the interaction and minimi^ the costs. Larvae of many species of lycaenid butterflies secrete nutritious food rewards to attending ants and, in return, receive protection against predators and parasitoids. Because ants typically recruit more workers to larger resources, by forming groups the larvae may ensure more reliable access to ants and thereby gain better protection. A further consequence of aggregating should be a change of the cost-benefit relationship for individual larvae. The larger the group, the smaller a single larva's influence will be on total ant density, which could lead to a smaller investment in secretion, thus reducing the per capita cost of cooperation. In this study, die influence of ant attendance, group size, and companion quality on larval investment was investigated. The interaction between the obligately ant-dependent lycaenid, Jcdmtnus evagoras, and its attendant hidomyrmtx ants was manipulated and the effect on larval secretion measured. As the level of ant attendance increased, the delivery of food rewards increased, bodi for solitary and for aggregated larvae. When aggregated, larvae provided less food rewards to ants dun when solitary, and secretion rate decreased with increasing group size. Furthermore, larvae had lower secretion rates when paired with a bigger, more attractive larva than when paired with a smaller one. The considerable reduction in secretion rates for larvae in groups suggests that gaining protection at a lower secretion cost could be one factor that promotes aggregation in myrmecophilous lycaenids.

Cooperation vs. exploitation: interactions between lycaenid (Lepidoptera: Lycaenidae) larvae and ants

Cooperation vs. exploitation: interactions between lycaenid (Lepidoptera: Lycaenidae) larvae and ants

Signalling in a mutualistic interaction

The costs and benefits for partners in interspecific, mutualistic relationships can vary from one interaction to the next, or change with time during an interaction, which might influence the mutualistic contributions. Such flexible behavioural responses could be important in regulating the interaction. Partners could also have special adaptations for the purpose of influencing each other. An individual might, for instance, signal its need for the services provided by the partner. In interactions between lycaenid butterfly larvae and ants, the larvae deliver nutritious droplets from a specialized gland and, in return, are protected from enemy attacks by the ants. Lycaenid larvae have several ant-related adaptations, one being a pair of eversible tentacular organs. In this study, the relationships between tentacle display, the delivery of droplets and ant attendance were investigated in a number of experiments, where the interaction between larvae of Polyommatus icarusand either Lasius nigeror L. flavus ants was manipulated. High rates of both droplet delivery and tentacle display were found at the first contact with ants, after an interruption in attendance and, for low levels of attendance, after a simulated enemy attack. Under steady state conditions, displays were most frequent at low levels of attendance, but droplet delivery had a maximum at intermediate levels. Manipulation of a larva's ability to use its tentacles also showed that ants respond to tentacle display by increasing their attendance. Larval behaviour was interpreted as aimed at regulating the number of attending ants.

Host‐plant relationships of lycaenid butterflies: large‐scale patterns, interactions with plant chemistry, and mutualism with ants

AbstractThe Lycaenidae are the second‐largest family of butterflies. From host‐plant data collated for more than 1200 species worldwide, large‐scale taxonomic, geographical and ecological patterns emerge which suggest that phytochemical similarities and barriers, coupled with phylogenetic conservatism and constraints are key factors governing host‐plant use. More than two thirds of the lycaenid species are restricted to one plant family or genus. Affiliations with ‘toxic’ plants are rare in the Lycaenidae, and excretion rather than sequestration of plant toxins appears to be their usual way of detoxifying host‐plant compounds. Flavonoids are frequently sequestered by lycaenid larvae and are subsequently concentrated as pigments in the adults' wings, where they might play a role in visual communication. Mutualistic associations with ants occur in the larvae of more than 50% of the extant Lycaenidae species. Because of a conflict between the nutrient demands of the larvae and the proportion of plant‐derived resources allocated to maintain the mutualism with ants, variation in resource quality often translates into variation of mutualistic capacities of the caterpillars, in particular under nutrient stress.

The influence of ants on patterns of colonization and establishment within a set of coexisting lycaenid butterflies in a south-east Asian tropical rain forest.

In Peninsular Malaysia ten species of lycaenid butterflies use leaf flushes or inflorescences of the legume tree Saraca thaipingensis as larval hostplant. Resource partitioning among these species is regulated by a complex mixture of patterns of interaction with ants. Females of obligately myrmecophilous species lay their eggs exclusively on trees colonized by their specific host ants. On trees colonized by weaver ants, only specialist mutualists adapted to these territorial ants are able to survive, while larvae of other species are killed. The formicine ant Cladomyrma petalae, which inhabits hollow twigs of the myrmecophytic hostplant, likewise precludes oviposition by female butterflies. Lycaenid larvae confronted with this ant species never survive, but one concealed feeding species (Jamides caeruleus) escapes removal due to the cryptic life-habits of the larvae. Two facultative myrmecophiles associate in a mutualistic way with a wide and largely overlapping range of ant genera which forage at the extrafloral nectaries of leaf flushes. One species (Cheritra freja) is not myrmecophilous, but is tolerated by all but the most territorial ants. Ant-dependent hostplant selection and egg-clustering characterize the obligate mutualists, whereas facultative myrmecophiles and the non-myrmecophile distribute their eggs singly over appropriate hostplants. Signals mediating caterpillar-ant communication are highly specialized in one obligate myrmecophile (Drupadia theda), but rather unspecific in four other species tested. Altogether our observations indicate that colonization and establishment of lycaenid butterflies on S. thaipingensis trees are governed by specializations as well as opportunistic use of resources (ants and hostplant parts). Therefore, the diversity of this species assemblage is maintained by deterministic as well as stochastic factors.

Assessing Benefits to Both Participants in a Lycaenid‐Ant Association

We examined interactions between the ant Iridomyrmex nitidiceps and the lycaenid butterfly Paralucia aurifera in southeastern Australia, and present data supporting the hypothesis that both participants benefit from their association. In the field, lycaenids persisted only on those host plants that ants subsequently colonized. In the laboratory, lycaenid larvae reared with ants were 31—76% heavier, developed 37% faster, and commonly completed one or two fewer instars than larvae reared without ants. Ant tending also resulted in 20% heavier pupae, 69% shorter pupal duration, and 5% larger adults as measured by forewing length; adults were not significantly different as measured by body length. We hypothesize that these positive effects occurred largely because ant—tended lycaenid larvae spent more time feeding than did untended larvae. Field data documented that ants colonized host plants only after lycaenid larvae were present, indicating that ants actively maintained the association. In laboratory experiments, 40% more ant workers survived when lycaenid larvae were present than when they were absent, although ant mass was not significantly affected. We hypothesize that the survivorship effects occurred because ants consumed the lycaenid's nectary gland secretions, which contained considerable amounts of glucose and amino acids. Our results showed that lycaenids can benefit from ants in ways other than, or in addition to, protection from natural enemies and that they incur minimal developmental costs from associating with ants.

Strategic behaviour in an interspecific mutualism: interactions between lycaenid larvae and ants

Abstract. Interspecific mutualism often involves partners trading different services. If it is costly to provide a service, there is a conflict of interest, and mutualism cannot be evolutionarily stable unless partners react to each other's contributions. An individual might also be influenced by its need for the services offered, being more willing to contribute when the need is greater. In mutualistic interactions between lycaenid butterfly larvae and ants, the larvae secrete nutritious droplets from a specialized gland and, in return, the ants protect the larvae from attacks by parasitoids and predators. Here, two aspects of the interactions between larvae of the common blue, Polyommatus icarus, and ants were studied experimentally. First, larval reaction to ant attendance was investigated by giving varying numbers of ants, Lasius flavus, access to a larva. The amount of larval secretion increased with the level of ant attendance, but at high levels no further increase occurred. Second, the effect of variation in a larva's need for protection was studied in an experiment where ants, Tetramorium caespitum, had free access to a larva. Exposing the larva to a simulated attack resulted in increased secretion and increased ant attendance. The effect on secretion was stronger; the number of droplets per attending ant was higher after an attack, making the interaction more favourable for the ants.