Natural history of an ant–plant–butterfly interaction in a Neotropical savanna

Non-myrmecophilous lepidopteran larvae using plants bearing ant attractants such as extrafloral nectaries are good models for studying morphological and behavioural mechanisms against ant predation. Udranomia spitzi (Hesperiidae) is a butterfly whose larvae feed on leaves of Ouratea spectabilis (Ochnaceae), a plant with extrafloral nectaries. We described the early stages of U. spitzi, and used field observations and experiments to investigate the defensive strategies of caterpillars against predatory ants. Larvae pass through five instars and pupation occurs inside larval leaf shelters. Ant-exclusion experiments revealed that the presence of ants did not affect significantly caterpillar survival. Predation experiments showed that vulnerability to ant predation decreased with increase in larval size. The present study showed that predatory ants are not as relevant as demonstrated for other systems, and also illustrates how observational data and field experiments can contribute to a better understanding of the biology and ecology of a species of interest.     

Effects of different ant species on the attendance of neighbouring hemipteran colonies and the outcomes for the host plant

Ants commonly participate simultaneously in mutualisms with honeydew-producing hemipterans and extrafloral nectar-bearing host plants. These interactions are based on the exchange of resources (honeydew and extrafloral nectar) for ant protection against natural enemies. The benefits may vary according to the species of ant interacting, and the outcomes for the host plant and hemipteran will depend on the results of the ant-plant-hemipteran relationship as a whole. We studied a plant-mealybug association with Camponotus crassus Mayr (Formicinae) and Ectatomma tuberculatum Olivier (Ectatomminae) in a Brazilian tropical savanna. We aimed to elucidate whether the frequency of visitation by different species of ants can be affected by neighbouring colonies of mealybugs, and whether these ant species influence the number of hemipterans in a different way. Furthermore, we intended to find out whether the interaction between ant and hemipteran has any effect on the proportion of fruit production or on the abundance of trophobiont and non-trophobiont herbivores, also influenced by the ant species. Our results show that neighbouring aggregations of mealybugs influenced the frequency of ant visitation and the ants affected the number of nymphs over time, with both positive results only for C. crassus. We also detected an indirect negative effect on proportion of fruit production and an increase in abundance of trophobiont and non-trophobiont herbivores in the presence of C. crassus-mealybug interaction. Thus, we provide further evidence that colonies of hemipterans interacting with ants can be beneficial for these herbivorous insects, but they are quite harmful to the host plant. Nevertheless, the outcomes can be highly conditional in relation to ant species.     

Extrafloral nectaries mediate the arboreal beetle community (Coleoptera) in a Neotropical rainforest

ABSTRACT

Nectaries are structures that secrete a sugary solution and can occur on vegetative and/or reproductive parts of plants. The significance of floral nectaries to reward vertebrate and arthropod pollinators is well supported. The role of extrafloral nectaries (EFNs) is more ambiguous, though research has been skewed to the ant-plant mutualism. Many other insects feed at EFNs, but these interactions are vastly understudied. This study addresses the hypothesis that EFNs may influence the occurrence and structure of Neotropical canopy beetle communities. Seven canopy trees (four families) exhibiting EFNs and their associated beetles were studied over a one-year period in southern Venezuela. In total, 6818 adult beetles identified to 868 species were recorded on 25 investigated canopy tree species (#47 individuals). Of the 868 beetle species, 150 species (517 individuals; 17.3% species) from 20 families were observed drinking from foliar EFNs on seven EFN-bearing tree species. Dietary dependence on EF nectar varied, with 95 beetle species utilising this nectar within a broader diet and 55 species found feeding exclusively on EFNs. This study demonstrates unequivocally that EF nectar is a frequently utilised food resource of many beetle adults and beetles have been a significantly underestimated visitor group. A more detailed study was conducted on six individual canopy trees of two species of Chrysobalanaceae, Licania hebantha Mart. ex Hook. f. and Moquilea subarachnophylla (Cuatrec.) Sothers and Prance. In total, 115 individual adults of 64 beetle species were collected on nectar secreted on newly-sprouted leaves. These beetle assemblages were dominated by species utilising EF nectar and were associated with distinct phenological phases of the host trees. Altogether, the beetle survey found support for the hypothesis that EFNs influence the occurrence and structure of beetle communities. These beetle-EFN relationships have implications for spatial arrangement, community assembly and evolution of both host plants and beetles. Like ant-EFN mutualism, EFN-bearing trees and beetles may also form mutualism. It is possible that the plants offer easier access to a nutritious resource that may deflect herbivory of vegetative parts.     

Polyphagy and florivory prevail in a leaf-beetle community (Coleoptera: Chrysomelidae) inhabiting the canopy of a tropical lowland rainforest in southern Venezuela

ABSTRACT

Embedded within the interdisciplinary research project ‘Towards an understanding of the structure and function of a Neotropical rainforest ecosystem with special reference to its canopy’ organised by the Austrian Academy of Science, the canopy beetle fauna was surveyed by means of a 42 m tall tower crane. This paper presents results of the chrysomelid beetle fauna observed and collected at canopy trees for 1 year. A total of 1783 adult leaf beetles were collected, representing 117 morphospecies (Bruchinae are not included) including 31 singletons. The most abundant family was Galerucinae sensu stricto with 827 individuals (46% of collection). The most speciose subfamilies were Galerucinae sensu stricto followed by Alticini, Cryptocephalinae and Eumolpinae. Nineteen species collected with at least two individuals were restricted to a single tree species whereas 68 species were found to feed on several canopy host trees. Only a few species fed on leaves; these were in Cassidinae, Cryptocephalinae, Eumolpinae and Galerucinae. Strikingly, most canopy chrysomelids were collected at flowers of canopy trees, although some species fed also on extrafloral nectaries or fruits. Alticini were restricted predominantly to flowers, but Cryptocephalinae, Eumolpinae and Galerucinae revealed broader plasticity in host tissue selection. Insights into beetle seasonality, diurnal/nocturnal activity and intra-canopy migration are provided. Abundant flower-visiting species occurred on their host trees commonly over the entire flowering season, with their abundances often correlated with the number of open flowers. After termination of one tree’s flowering season, many flower-visiting leaf beetles moved to other flowering trees. Certain congeneric species of Galerucinae and Eumolpinae occurred together at their host plants within the same periods.     

Do caterpillars of Dryas iulia alcionea (Lepidoptera,Nymphalidae) show evidence of adaptive behaviour to avoid predation by ants?

Plants bearing extrafloral nectaries can attract wasps, bugs, and mainly ants. Ants can defend plants against herbivores by treating the plant as an extension of their own territory. We evaluated the efficiency of resting sites built by Dryas iulia alcionea larvae as protection against ant predation on their host plant Passiflora suberosa. The results showed that ants on P. suberosa have significant influence on the survival of D. iulia caterpillars. The use and construction of resting sites was recorded through the fourth larval stadium. A strong inverse relationship between the number of resting sites constructed per larva and the developmental stage of the larvae was observed. Additional results suggest that the efficacy of resting sites against cursorial predators decreases with larval development. The behaviour of constructing resting sites probably evolved by natural selection. It is likely that this behaviour was important for the ancestral lineage that gave origin to Heliconiinae genera Dryas, Dryadula and Phylaethria.     

Ecology and field biology of two dominant Camponotus ants (Hymenoptera: Formicidae) in the Brazilian savannah

Camponotus renggeri and C. rufipes are very abundant in Brazilian cerrado savannah, where they feed extensively on liquid rewards and commonly associate with plants bearing extrafloral nectaries and honeydew-producing insects. Here, we provide a qualitative and quantitative field account on the natural history and ecology of these two ant species. The study was carried out in a cerrado reserve in south-eastern Brazil across a rainy/hot season (summer) and a dry/cold season (winter). The ants were found in two vegetation physiognomies: all nests of C. rufipes were located in the cerrado sensu stricto (scrub of shrubs and trees, 3–8 m tall), whereas C. renggeri occurred mostly in the cerradão (forest with more or less merging canopy, 10–12 m tall). Both species nested in fallen or erect dead trunks, as well as underground. In addition, C. rufipes built nests using dead plant material arranged or not around shrub bases. Colonies of C. rufipes were generally more populous than those of C. renggeri, and both species had colonies with more than one dealated queen. Both species were active mainly at night and foraged for resources near their nests, mainly extrafloral nectar and hemipteran honeydew (aphids and mealybugs). The average size of the home ranges of C. renggeri in cerrado sensu stricto and cerradão varied from ≈ 2.8 to 4.0 m² and apparently were not affected by season. In C. rufipes, however, foraging grounds in cerrado sensu stricto showed a twofold increase from dry/cold (≈ 4.5 m²) to rainy/hot season (≈ 9.8 m²). Our study highlights the importance of natural history data to understand the foraging ecology and role of these ants in cerrado savannah.     

Correlation of heteromorphic life instars in terrestrial Parasitengona mites and its impact on taxonomy – the case of Leptus molochinus (C. L. Koch, 1837) and Leptus ignotus (Oudemans, 1903) (Acari: Trombidiformes: Prostigmata: Erythraeidae)

Preference–performance hypothesis was tested in the butterfly Heliconius erato phyllis under field, insectary and laboratory conditions in a population from southeastern Brazil. Throughout a year, Passiflora capsularis was the host predominantly used for oviposition in the field. Similarly, when host plants were of high quality in the field, H. erato phyllis females that came from this environment laid more eggs on P. capsularis under insectary conditions. In contrast, when host plant quality declined in nature, females did not show preference for any host plant in particular in the insectary. Larvae had superior performances when reared on P. capsularis and Passiflora edulis than on Passiflora jilekii. Overall, our results show a trend towards a positive relationship between oviposition and performance in H. erato phyllis. The factors that might lead to an absence of selection under insectary conditions by females from a poor-quality environment are discussed.     

Adult butterfly feeding–nectar flower associations: constraints of taxonomic affiliation,butterfly, and nectar flower morphology

Butterfly–flower morphological interrelationships were investigated for 108 butterfly species and 20 plants at Nagpur, India. Distinct clusters of higher taxa (families) are disclosed for butterfly morphology and significant morphological and taxonomic associations occur in nectar exploitation. Flower corolla depth generally restricts exploitation by butterflies in relation to proboscis length and butterflies with high wing load indices bias their feeding to plants with massed flowers. However, important exceptions emerge; also, a substantial number of butterflies feed on plants with massed flowers though their proboscises are of marginal length for corolla depths. These butterfly species are significantly smaller, lighter, with lower wing loading and shorter proboscis indices than species which easily access the same flowering plant species. It is suggested that small size and short proboscises could give them a competitive advantage (increased rate of nectar uptake) for exploiting nectar in such situations. The significance of the findings for conservation is discussed.     

The natural history of the parasitic wasp Trogus pennator (Hymenoptera: Ichneumonidae): Host‐finding behaviour and a possible host countermeasure

The parasitic wasp Trogus pennator (Ichneumonidae) attacks the larvae of swallowtail butterflies (Papilionidae). Female T. pennator were followed in the field as they searched for larvae of the zebra swallowtail butterfly, Eurytides marcellus (Papilionidae), feeding on Asimina (Annonaceae) in central Florida, USA. Predictions of host‐finding theory and interactions with the host were thus investigated in a natural setting. Wasps seldom flew to plants other than Asimina and apparently recognized the plants by visual cues. Plants were attractive regardless of host presence, as the wasps approached plants lacking E. marcellus feeding damage twice as often as they approached damaged plants. However, wasps approached damaged plants at a rate greater than their frequency in the Asimina population, indicating that they can detect host damage before they approach the plants. After approaching within 0.5?m of plants, wasps tended not to land on plants lacking feeding damage. A comparison of the plants they landed on, however, showed no consistent preferences for damaged plants. The weaker trends in the latter data indicate that the presence of feeding damage was not the sole criterion for landing, although it evidently influenced behaviour. After landing, wasps spent more time searching damaged plants than undamaged plants. Butterflies preferred to oviposit on plants shorter than those searched by T. pennator. Possible adaptive consequences of this phenomenon are discussed.     

Ant–herbivore interactions in an extrafloral nectaried plant: are ants good plant guards against curculionid beetles?

Extrafloral nectary drinking ants are known as effective plant guards, but some herbivores may circumvent ant attacks by foraging on different plant parts or presenting adaptations to avoid ant predation. Here we experimentally investigated the effect of Camponotus blandus on the florivory of the extrafloral nectaried shrub Banisteriopsis malifolia; and a possible spatial segregation between ants and herbivores (leaves and flowers). Flower buds are attacked by Anthonomus weevils. Results revealed no significant influence of C. blandus on the reduction of florivory. Adult Anthonomus are hard-bodied and were immune to ant bites; larvae are endophytic, so protected from ants. Ants and adult beetles were concentrated in different plant parts (leaves and flowers, respectively) so restraining the probability of encounters. Our results indicate that the system C. blandus–Anthonomus–B. malifolia is not stable, as ants receive extrafloral nectar, but are unable to protect the plant against weevils.     

Geographic distribution,host plants,and morphological variation of the currently radiating phytophagous ladybird beetle Henosepilachna diekei

To overview the morphological and ecological diversification within a species of phytophagous ladybird beetle Henosepilachna diekei, information concerning its distribution and host plant use was studied. This species was found widely in South East and South Asia from the Philippines through the Greater Sunda islands, a western part of Lesser Sundas, the Malay Peninsula to Sri Lanka. Mikania species (Asteraceae), Mikania micrantha in particular, were the most frequently used host plants, but some other plants belonging to Lamiaceae or Acanthaceae were also used by some local populations. Each population is possibly monophagous. According to morphological analyses, seven populations from four host plants at six sites on four Indonesian islands were grouped into two, one occurring on Java and Kalimantan (Borneo) and another on Sulawesi and Lombok, indicating that they were separated by the Wallace line. This morphological distinction was not correlated with the host plant use.     

The tortoise caterpillar: carnivory and armoured larval morphology of the metalmark butterfly Pachythone xanthe (Lepidoptera: Riodinidae)

ABSTRACT

The natural history and morphology of the later instars and pupa of the metalmark butterfly Pachythone xanthe H. Bates are described and illustrated for the first time. The caterpillars are myrmecophilous and carnivorous, feeding on scale insects (Hemiptera: Coccoidea) tended by Azteca cf. chartifex Forel (Formicidae: Dolichoderinae) ants and appear to be physically shielded from potential ant attacks by a carapace-like body that protects the head and appendages. In addition, the larvae present several types of specialised setae and ant-organs such as perforated cupola organs, glandular openings and functional tentacle nectary organs that may be related to appeasement of aggressive ant behaviour. Our results reveal the first detailed life cycle data for the Pachythonina subtribe and record a new independent origin of carnivory in Riodinidae.     

Afrotropical mistletoe butterflies: Larval food plant relationships of Mylothris Hübner (Lepidoptera: Pieridae)

A detailed list of larval food plants of Mylothris based on review of published records in the literature is presented. Food plants have been reported for some 23 species (40%), although in only eight species (14%) of butterflies have plants been identified to species level. The food plants represent two unrelated orders, Santalales and Polygonales, although nearly all records (93%) are from four closely related families in the former group. Within the Santalales, the family Loranthaceae, a diverse group of aerial stem‐parasitic shrubs (mistletoes), is most frequently exploited. Only two species of Mylothris, M. bernice (Hewitson) and M. rubricosta (Mabille), which are closely related and possibly comprise a single species, are associated with Polygonaceae (Polygonales). Comparison of the morphology of the early stages of M. bernice, and other evidence, clearly indicates that M. bernice/rubricosta belong to Mylothris and do not represent a separate genus or sister group. Comments are made on these diverse food plant relationships within the context of a modern phylogeny of the Santalales and the evolution of parasitic plant feeding in butterflies in general. It is suggested that Mylothris had its major period of evolution and adaptive radiation on the Loranthaceae, probably sometime after the differentiation of most of the families or lineages in the Santalales (rather than on an earlier ancestral branch at or near the root of the Santalales evolutionary tree), and that this association has facilitated host switching multiple times. While more field data are clearly needed to ascertain the full extent of host specificity and range of mistletoe species exploited by Mylothris, this is unlikely to significantly change the patterns of food plant utilization seen at the higher taxonomic (ordinal and familial) levels. Mylothris represents one of only a few diverse groups of Lepidoptera, and insects in general, known to feed predominantly on African mistletoes.     

Revision of the Neotropical genus Yagra Oiticica (Lepidoptera: Castniidae)

The Castniidae, or butterfly moths, are characteristically colourful diurnal moths, distributed throughout the tropics except in Africa. The Neotropical representatives forage almost exclusively on monocotyledonous plants and many species are crop pests with more than 60% of the Neotropical castniids found or endemic in Brazil. Research studies that focus on taxonomy, systematics, and morphology of this group are scarce. In this study, Yagra Oiticica, a small genus restricted to south-eastern South America, is revised and the diagnostic morphological characters of male and female genitalia are illustrated. This research is part of long-term study on the Castniidae for future phylogenetic analysis.     

The myrmecophilous organs of larvae of the small blue,Cupido minimus (Lepidoptera; Lycaenidae)

Larvae of the lycaenid butterfly Cupido minimus have been examined using scanning electron microscopy following critical-point drying. They were found to possess both dorsal organs and pore cupolae, organs associated with myrmecophily. These results are compared with those of earlier authors and their significance discussed.     

Multi-scale patterns in the host specificity of plant-dwelling arthropods: the influence of host plant and temporal variation on species richness and assemblage composition of true bugs (Hemiptera)

The influence of temporal variation in the host specificity of invertebrates to estimates of biodiversity is rarely considered. While patterns at large spatial scales have stimulated much attention, such comparisons are constrained for southern-hemisphere biomes because the patterning of invertebrates on plants is largely unknown. Here, we analyse variation of plant-dwelling Hemiptera from 15 understorey plant species over 18 months in the south-west Australian biodiversity hotspot. Analyses showed significant interactions in species composition between sampling period and plant species. Fauna that were “effectively specialized” (host-specificity index) to plants changed with season, although this was also related to the number of singletons and overall species richness. Sampling from a single season also overestimated the degree of host specificity by 52% and underestimated the perception of species richness when an outbreak of a particular herbivore occurred. High host-specificity values (12.7 hemipteran species per plant) support the case for high estimates of global arthropod richness.     

Larval development of the fiddler shrimp,Metapenaeopsis stridulans (Alcock, 1905) (Decapoda: Penaeidae) reared in the laboratory

Larvae of Metapenaeopsis stridulans (Alcock, 1905) from Malaysia were successfully reared in the laboratory from the egg to the 1st post-larval stage. The larvae developed through six naupliar, three protozoeal and four mysis stages. The morphology of all these larval stages is described and figured.     

Distribution of bisexual and unisexual species in the aphid genus Colopha Monell (Aphididae: Eriosomatinae), with the description of a new species in Japan

Aphids of the genus Colopha are represented by three bisexual and three unisexual species. The bisexual species are associated with two Ulmus species that are most closely related, being distributed disjunctively in Europe and eastern North America on the host plants. A new unisexual species of Colopha, collected from Setaria chondrachne (Poaceae) in Japan, is described under the name Colopha setaricola sp. nov. The distribution of the three unisexual species is discussed in relation to aphid‐plant associations and historical changes in the distribution of the host plants. It is suggested that these unisexual species have persisted on the secondary hosts through parthenogenetic reproduction since the extinction of the primary host plants, Ulmus species section Blepharocarpus. Therefore, the unisexual species in Colopha exemplify Mordvilko's hypothesis that unisexual species on the secondary host plants have remained as relics in the region where the primary host was once distributed but then became extinct.