Ant Predation Research Articles

Toxicity and residual effects of insecticides on Ascia monuste and predator Solenopsis saevissima.

Investigating the impact of pesticides on non-target organisms is essential for sustainable integrated pest management programs. We therefore assessed the toxicity of ten insecticides to the brassica caterpillar Ascia monuste and its ant predator Solenopsis saevissima and examined the effect that the insecticide synergists had on toxicity to the predator. We also assessed the residual period of control and impact of the insecticides during the brassica growing cycle. All insecticides except flubendiamide exhibited mortality above the threshold required by Brazilian legislation (80%). Chlorantraniliprole, cyantraniliprole, indoxacarb and spinosad exhibited lower toxicity to the ant predator than they did to the brassica caterpillar. The results obtained for synergized insecticides suggest that selectivity to the predator was due the involvement of cytochrome P450-dependent monooxygenases. Chlorfenapyr and cyantraniliprole exhibited the highest residual periods of control to the brassica caterpillar, whereas malathion had the greatest impact on the predator. Most of the insecticides efficiently controlled the brassica caterpillar, but not all exhibited selectivity to the predator. Therefore, due to the distinctive responses of organisms with respect to residual periods of control and the impact of the insecticides, spraying frequency must be strongly considered in integrated pest management programs. © 2017 Society of Chemical Industry.

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.

Effects of predatory ants within and across ecosystems in bromeliad food webs.

Predation is one of the most fundamental ecological processes affecting biotic communities. Terrestrial predators that live at ecosystem boundaries may alter the diversity of terrestrial organisms, but they may also have cross-ecosystem cascading effects when they feed on organisms with complex life cycles (i.e. organisms that shift from aquatic juvenile stages to terrestrial adult stages) or inhibit female oviposition in the aquatic environment. The predatory ant Odontomachus hastatus establishes its colonies among roots of Vriesea procera, an epiphytic bromeliad species with water-filled tanks that shelters many terrestrial and aquatic organisms. Ants may impact terrestrial communities and deter adult insects from ovipositing in the water of bromeliads via consumptive and non-consumptive effects. Ants do not forage within the aquatic environment; thus, they may be more efficient predators on terrestrial organisms. Therefore, we predict that ants will have stronger effects on terrestrial than aquatic food webs. However, such effects may also be site contingent and depend on the local composition of food webs. To test our hypothesis, we surveyed bromeliads with and without O.hastatus colonies from three different coastal field sites in the Atlantic Forest of southeast Brazil, and quantified the effect of this predatory ant on the composition, density and richness of aquatic and terrestrial metazoans found in these bromeliads. We found that ants changed the composition and reduced the overall density of aquatic and terrestrial metazoans in bromeliad ecosystems. However, effects of ants on species diversity were contingent on site. In general terms, the effects of the ant on aquatic and terrestrial metazoan communities were similar in strength and magnitude. Ants reduced the density of virtually all aquatic functional groups, especially detritivore insects as well as metazoans that reach bromeliads through phoresy on the skin of terrestrial animals (i.e. Ostracoda and Helobdella sp.). Our results suggest that the cross-ecosystem effect of this terrestrial predator on the aquatic metazoans was at least as strong as its within-ecosystem effect on the terrestrial ecosystem, and demonstrates that the same predator can simultaneously initiate cascades in multiple ecosystems.

Can the absence of ants interfere in the arthropods abundance on corn plants (Zea mays L. - Poaceae)?

Alternative methods to reduce the chemical control in monoculture have been widely assessed in order to diminish the pesticide use. Thus, the efficiency of predator arthropods who work as population controllers in many agro-ecosystems has been tested. The current study aim to verify if the presence of ants interfere in the amount of arthropod herbivores and predators on corn plants, Zea mays L. (Poaceae). A total of 100 plants were assessed, out of them, 50 were isolated from ants and the other 50 were not. There were 25 taxa of arthropods on corn plants, in which 14 were herbivorous and 11 predators. The ants’ free access to the plants negatively influenced the Diabrotica speciosa (Germar, 1824) (Coleoptera: Chrysomelidae) amount, which is an important herbivorous plague in corn monoculture. It was also observed the greater amount of Doru sp.1 (Dermaptera: Forficulidae) on plants containing ants. Considering the assessed plants, the presence of ants did not influenced the abundance of other arthropods. These results suggest that the ant-plant-herbivore interactions in corn monoculture is a complex system, and the presence of predatory ants in plants not always influence the presence of other arthropods.

Paternal care behaviour of the giant water bug Kirkaldyia deyrolli (Heteroptera: Belostomatidae) against ants

1. Although potentially vulnerable to predators, the offspring of subsocial insects are effectively protected by their parent(s). The female giant water bug Kirkaldyia deyrolli lays its egg masses on the vegetation above the water surface in aquatic environments and the males supply the eggs with water and guard them against cannibalistic females until hatchling dispersal. Field observations showed that egg masses are attacked by ants if the attending males are not present.2. Laboratory experiments were conducted to evaluate the effects of paternal care by K. deyrolli against the ant Tetramorium tsushimae by means of four treatments: attending male with ant approach (WM‐WA); no attending male with ant approach (NoM‐WA); attending male without ant approach (WM‐NoA); and no attending male without ant approach (NoM‐NoA).3. The rate of offspring survival was lower in the NoM‐WA group (45.3%) than in any other group, which showed similar offspring survival (WM‐WA = 80.4%, WM‐NoA = 75.1%, NoM‐NoA = 80.3%). Moreover, there were a total of 44 interactions between the attending male and ants in WM‐WA, and of these, a chemical compound was released by the attending male four times; this probably deterred ants from attacking because the ants went back to their colony.4. In conclusion, the attending male can protect its eggs from ant predators and its care has an important role. To the best of the authors' knowledge, this is the first report of Lethocerinae males protecting their egg masses from ants by means of physical and chemical defence.

Effects of land‐use changes on ecosystem services: decrease in ant predation in human‐dominated landscapes in central Brazil

AbstractAnthropogenic disturbances often affect the abundance and diversity of ants (Hymenoptera: Formicidae) but relatively few studies have explored the implications of such changes on the ecosystem services mediated by these insects. Here, we evaluated how the transformation of Cerrado savanna habitats into crop plantations affects the abundance, diversity, and the predatory activity of ants. A survey of the ant faunas foraging above‐ and belowground was performed in six crop and six non‐crop (i.e., native vegetation) sites. Above‐ and belowground rates of ant predation were estimated at these same sites using mealworms, Tenebrio molitor L. (Coleoptera: Tenebrionidae), as baits, simulating crop herbivores. Belowground predation rates were significantly greater in the non‐crop sites, despite the lack of difference in overall abundance and species richness of ants foraging belowground between the crop vs. non‐crop sites. In contrast, we did not detect any significant difference in aboveground predation rates between crop vs. non‐crop sites even though there were significantly more species of ants foraging aboveground in the non‐crop sites. Army ants (subfamily Dorylinae) were the main predatory species belowground, and their abundance was significantly greater in non‐crop sites. In contrast, the main predators aboveground were omnivore ants of the genera Pheidole and Solenopsis, which had similar abundances in the crop and non‐crop sites. Overall, our results indicate that transformation of native Cerrado habitats into crop plantations reduces the abundance of some important predatory species, notably those that forage belowground, and this may negatively affect the potential for ants to provide pest control services in agroecosystems.

At Lunch with a Killer: The Effect of Weaver Ants on Host-Parasitoid Interactions on Mango.

Predator-prey interactions can affect the behaviour of the species involved, with consequences for population distribution and competitive interactions. Under predation pressure, potential prey may adopt evasive strategies. These responses can be costly and could impact population growth. As some prey species may be more affected than others, predation pressure could also alter the dynamics among species within communities. In field cages and small observation cages, we studied the interactions between a generalist predator, the African weaver ant, Oecophylla longinoda, two species of fruit flies that are primary pests of mango fruits, Ceratitis cosyra and Bactrocera dorsalis, and their two exotic parasitoids, Fopius arisanus and Diachasmimorpha longicaudata. In all experiments, either a single individual (observation cage experiments) or groups of individuals (field cage experiments) of a single species were exposed to foraging in the presence or absence of weaver ants. Weaver ant presence reduced the number of eggs laid by 75 and 50 percent in B. dorsalis and C. cosyra respectively. Similarly, parasitoid reproductive success was negatively affected by ant presence, with success of parasitism reduced by around 50 percent for both F. arisanus and D. longicaudata. The negative effect of weaver ants on both flies and parasitoids was mainly due to indirect predation effects. Encounters with weaver ant workers increased the leaving tendency in flies and parasitoids, thus reduced the time spent foraging on mango fruits. Parasitoids were impacted more strongly than fruit flies. We discuss how weaver ant predation pressure may affect the population dynamics of the fruit flies, and, in turn, how the alteration of host dynamics could impact parasitoid foraging behaviour and success.

Imidacloprid seed treatments affect individual ant behavior and community structure but not egg predation, pest abundance or soybean yield.

Neonicotinoid seed treatments are under scrutiny because of their variable efficacy against crop pests and for their potential negative impacts on non-target organisms. Ants provide important biocontrol services in agroecosystems and can be indicators of ecosystem health. This study tested for effects of exposure to imidacloprid plus fungicide or fungicide-treated seeds on individual ant survival, locomotion and foraging capabilities and on field ant community structure, pest abundance, ant predation and yield. Cohorts of ants exposed to either type of treated seed had impaired locomotion and a higher incidence of morbidity and mortality but no loss of foraging capacity. In the field, we saw no difference in ant species richness, regardless of seed treatment. Blocks with imidacloprid did have higher species evenness and diversity, probably owing to variable effects of the insecticide on different ant species, particularly Tetramorium caespitum. Ant predation on sentinel eggs, pest abundance and soybean growth and yield were similar in the two treatments. Both seed treatments had lethal and sublethal effects on ant individuals, and the influence of imidacloprid seed coating in the field was manifested in altered ant community composition. Those effects, however, were not strong enough to affect egg predation, pest abundance or soybean yield in field blocks. © 2016 Society of Chemical Industry.

The influence of invasive fire ants on survival, space use, and patterns of natural selection in juvenile lizards

Invasive species have altered natural communities and exposed native species to new selective pressures. These pressures are particularly acute when invasive species are predators of natives. The invasive red imported fire ant has expanded its range significantly in the southeast United States and has become an important predator of native species that share similar habitat preferences, like the prairie lizard, Sceloporus consobrinus. Recent studies indicate that lizards that have coexisted for a long period of time with fire ants have responded both plastically and adaptively to this invasion. However, despite considerable work, few “controlled” experiments have been conducted to explore the influence of fire ants on vertebrates in natural populations. In this study we released hatchling lizards on two experimental islands that differed in fire ant density to investigate the influence of fire ants on lizard survival, habitat/space use, and patterns of phenotypic selection. We demonstrate that fire ant presence significantly explains patterns of lizard survival among populations and over small spatial scales within populations. As a consequence of survival patterns or avoidance behavior, lizard habitat use was significantly altered in the presence of fire ants in high density. Finally, we found strong signatures of natural selection on lizard body size and body condition, but the patterns of selection did not appear to be influenced by variation in fire ant density. This study highlights the direct influence of predatory fire ants on hatchling lizard mortality and habitat use. These effects can have important demographic and population-level consequences.

Variation in Extrafloral Nectary Productivity Influences the Ant Foraging.

Extrafloral nectar is the main food source offered by plants to predatory ants in most land environments. Although many studies have demonstrated the importance of extrafloral nectaries (EFNs) to plant defense against herbivores, the influence of EFNs secretory activity pattern on predatory ants remains yet not fully understood. Here, we verified the relation between the extrafloral nectar production of a plant community in Cerrado in different times of the day, and its attractiveness to ants. The extrafloral nectaries (EFNs) of seven plant species showed higher productivity overnight. Ant abundance was higher in times of large extrafloral nectar production, however, there was no positive relation between ant richness on plants and EFNs productivity. There was temporal resource partitioning among ant species, and it indicates strong resource competition. The nectar productivity varied among plant species and time of the day, and it influenced the visitation patterns of ants. Therefore, EFNs are a key ant-plant interaction driver in the studied system.

The rove beetle Drusilla sparsa (Coleoptera: Staphylinidae) is a myrmecophilous species associated with a myrmicine ant, Crematogaster osakensis (Hymenoptera: Formicidae)

AbstractThe rove beetle genus Drusilla includes some myrmecophilous species. The Japanese species Drusilla sparsa (Sharp, 1874) has been regarded as a non‐myrmecophilous beetle. In Kagawa Prefecture, Shikoku Island, western Japan, however, we often observed that D. sparsa adults were walking in the vicinity of foraging workers of the myrmicine ant Crematogaster osakensis Forel, 1990. The body color of the beetle is similar to C. osakensis as in other myrmecophilous beetles found near the trails of the host ants. To examine whether D. sparsa is myrmecophilous, we investigated the distribution of D. sparsa and C. osakensis in the field, as well as their behavior including prey preference of the beetle in the laboratory. Drusilla sparsa beetles were collected only in sites where C. osakensis ants occurred. When the beetles encountered the ant workers, they bent the abdominal tip toward the ants. The ants licked the abdominal tip, and then the beetles usually walked away. Such behavioral reaction of the ants was not observed when the beetles encountered workers of the formicine ant Nylanderia flavipes (Smith, 1874) that continuously attacked the beetles. Drusilla sparsa preferred to feed on dead workers of C. osakensis even when other ants were available as food, indicating that D. sparsa is a myrmecophilous species associated with C. osakensis. Crematogaster osakensis was frequently found in the stomach in the ant predator, the Japanese treefrog Hyla japonica Günther, 1859. Thus, the significance of body color similarity between the host ants and beetles is not a case of Batesian mimicry.

Red Imported Fire Ants (Hymenoptera: Formicidae) are Unsuitable Prey for a Native Antlion (Neuroptera: Myrmeleontidae) in Florida

Summary We examined the suitability of Solenopsis invicta Buren (Hymenoptera: Formicidae) as prey for a native antlion, Myrmeleon crudelis Walker (Neuroptera: Myrmeleontidae), in south Florida. We found that average growth rate was significantly lower and mortality was significantly higher for M. crudelis larvae fed S. invicta workers than for M. crudelis larvae fed Dorymyrmex bureni (Trager) (Hymenoptera: Formicidae) workers. Thus, S. invicta appears to be unsuitable prey for M. crudelis and may have a negative impact on M. crudelis and other ant predators in areas where it invades.

The palatability of Neotropical poison frogs in predator‐prey systems: do alkaloids make the difference?

AbstractNeotropical poison frogs sequester alkaloid‐based chemical defenses from their diet, which seem to repel invertebrate predators after contact. In this study, we tested the reaction of predatory ants toward skin secretions of captive‐bred poison frogs without alkaloids. Although the secretions had a smell and taste similar to those of wild‐caught frogs, the ants did not avoid them, but actually preferred them. We infer that amphibian secretions are attractive to invertebrate predators (probably due to palatable nutritive components), but that this attraction is overridden when unpalatable alkaloids are present.

Ancestry trumps experience: Transgenerational but not early life stress affects the adult physiological stress response

Exposure to stressors can affect an organism's physiology and behavior as well as that of its descendants (e.g. through maternal effects, epigenetics, and/or selection). We examined the relative influence of early life vs. transgenerational stress exposure on adult stress physiology in a species that has populations with and without ancestral exposure to an invasive predator. We raised offspring of eastern fence lizards (Sceloporus undulatus) from sites historically invaded (high stress) or uninvaded (low stress) by predatory fire ants (Solenopsis invicta) and determined how this different transgenerational exposure to stress interacted with the effects of early life stress exposure to influence the physiological stress response in adulthood. Offspring from these high- and low-stress populations were exposed weekly to either sub-lethal attack by fire ants (an ecologically relevant stressor), topical treatment with a physiologically-appropriate dose of the stress-relevant hormone, corticosterone (CORT), or a control treatment from 2 to 43weeks of age. Several months after treatments ended, we quantified plasma CORT concentrations at baseline and following restraint, exposure to fire ants, and adrenocorticotropic hormone (ACTH) injection. Exposure to fire ants or CORT during early life did not affect lizard stress physiology in adulthood. However, offspring of lizards from populations that had experienced multiple generations of fire ant-invasion exhibited more robust adult CORT responses to restraint and ACTH-injection compared to offspring from uninvaded populations. Together, these results indicate that transgenerational stress history may be at least as important, if not more important, than early life stress in affecting adult physiological stress responses.

Multiple interaction types determine the impact of ant predation of caterpillars in a forest community.

Direct and indirect effects of predators are highly variable in complex communities, and understanding the sources of this variation is a research priority in community ecology. Recent evidence indicates that herbivore community structure is a primary determinant of predation strength and its cascading impacts on plants. In this study, we use variation in herbivore community structure among plant species to experimentally test two hypotheses in a temperate forest food web. First, variation in the strength of predator effects, such as ant predation of caterpillars, is predicted to be density dependent, exhibiting stronger effects when prey abundance is high (density-dependent predation hypothesis). Second, mutualistic interactions between ants and sap-feeding herbivores are expected to increase the abundance of predatory ants, strengthening predation effects on herbivores with cascading effects on host plants (keystone mutualism hypothesis). Using a large-scale predator exclusion experiment across eight dominant tree species, we tracked changes in insect density on 862 plants across two years, recording 2,322 ants, 1,062 sap-feeders, 5,322 caterpillars, and quantifying herbivory on 199, 338 leaves. In this experiment, density-dependent predation did not explain variation in the direct or indirect effects of ants on caterpillars and herbivory. In partial support of the keystone mutualism hypothesis, sap-feeders strengthened top-down effects of ants on caterpillars under some conditions. However, stronger ant predation of caterpillars did not lead to measurable trophic cascades on trees occupied by sap-feeders. Instead, the presence of sap-feeders was associated with increased per capita feeding damage by caterpillars, and this bottom-up effect attenuated the indirect effects of ants on host plants. These findings demonstrate that examining the multi-trophic impacts of mutualisms and predation in the context of the broader community can reveal patterns otherwise masked by compensatory interactions.

Parasites-Predators:Their Occurrence and Invasive Impact on the Tropical Tasar Silkworm <I>Antheraea mylitta</I> (Drury) in the Zone of Central India

Tasar silk is produced by the wild silkworm Antheraea mylitta (Drury) (Lepidoptera: Saturniidae). Owing to its inherent wild nature, the silkworm is exposed to a complex of parasites, predators and diseases that reduce the total silk production. Occurrence and invasion by three parasites and nine predators of A. mylitta are studied here. Moreover, on the basis of their attack and symptoms of parasitism and/or predation, percentage of crop loss (mortality) of A. mylitta is calculated. The parasites including Xanthopimpla pedator (Fabricius) (Hymenoptera: Ichneumonidae) were observed as a major pupal endoparasitoid of A. mylitta , which affects about 7-12% of tasar cocoon. In addition, the beetle Dermestes ater (De Geer) (Coleoptera: Dermestidae) also affects the pupa/cocoon of A. mylitta , while the Tachnid fly, Blepharipa sp., recognized as a larval-pupal parasite of the silkworm, cause about 1- 2% and 2-3% of tasar crop loss respectively. Consequently, among the predators, Canthecona furcellata (Wolff) (Pentatomidae: Hemiptera), was observed as a major predator of A. mylitta that causes about 6-11% of tasar larval mortality. However, 2-3% and 3-4% of crop mortality occurs due to predation by Hierodula bipapilla (Serville) (Mantidae: Dictyoptera) and Vespa orientalis (Linnaeus) (Vespidae: Hymenoptera) respectively. The predatory ants Oecophylla smaragdina (Fabricius) (Formicidae: Hymenoptera) and Myrmicaria brunnea (Saunders) (Formicidae: Hymenoptera) also contribute to crop reduction by 4-5% and 3-5% respectively. Similarly, non-insect predators such as birds, lizards, squirrels, rats, etc. also affect the silkworm, which further reduces tasar silk production. Therefore, a survey was undertaken in the tasar rearing fields of Vidarbha, Maharashtra, India and the occurrence of the parasites and predators was studied.

EVALUATION OF NATURAL ENEMIES IN CONTROLLING OF THE BANANA WEEVIL BORER Cosmopolites sordidus Germar IN WEST SUMATRA

<br />The banana weevil, Cosmopolites sordidus Germar, is an important pest of highland banana and plantain in Africa, but it exists in low densities in presumed area of origin in Southeast Asia such as in Indonesia. This suggests a possible existence of effective co-evolved natural enemies in the origin area of Indonesia, especially West Sumatra. The objectives of this study were: (1) to evaluate banana weevil pest status at selected sites in West Sumatra, (2) to survey parasitoids and predators, and (3) to determine the control potential of the most important natural enemies. Surveys were undertaken in March 2002-August 2003 in five locations in West Sumatra, i.e., Bukittinggi, Sitiung, Pariaman, Pasaman, and Batusangkar. Five farms per site were selected randomly among all farms that contained banana stands of > 0.5 ha. Sampling for banana weevil adults and damage, and for predators was done throughout small banana stands and within a 20 m x 40 m (0.08 ha) subplot on larger farms. Field-collected larvae were taken to the laboratory and reared on corm pieces (3 cm x 3 cm x 3 cm) until pupation. Larvae were collected from pseudostem as well as corm residues. To estimate the abundance of non-social predators, i.e., those other than ants, 10 residues each on each farm were examined from plants that had been harvested 1-4 weeks, 5-8 weeks or 9 or more weeks before our visit to the site. Samples of the different morphospecies were saved in alcohol for later identification. The result showed that the banana weevil incidence was found to be low, 0.6-1.7 adults per trap. Plant damage indices were below 2.2%. We collected and reared 24,360 eggs and 3118 larvae, but no parasitism was detected. Phorids (Megaselia sp.) and drosophilids were recovered from larval rearings, but most likely were scavengers. A complex of predators was detected, the most important of which was the histerid beetles, <em>Plaesius javanus </em>Erichson. In laboratory tests, adults and larvae of P. <em>javanus</em> attacked 75-88% and 38-53% of banana weevil larvae and pupae, respectively. Predatory ants, including species of Myrmicinae, Ponerinae, Formicinae, and Dolichoderinae, were found to be associated with banana plants and residues. Adults of Myopopone castanea Smith (Ponerinae) were directly observed attacking banana weevil larvae in crop residues. The adult banana weevil mortalities caused by the entomopathogen fungi of Beauveria bassiana from Baso, Sungaitarab, Sei Sariek, and Sikabau at highest density (3.2 x 108 spores ml-1) after two weeks were 96.67%, 90.00%, 60.00% and 83.33%, respectively. The high diversity of habitat conditions in which crop-pest-natural enemies systems exist, support the idea that banana weevil population and damage intensity in the study area is low due to active role of natural enemies.

EVALUATION OF NATURAL ENEMIES IN CONTROLLING OF THE BANANA WEEVIL BORER Cosmopolites sordidus Germar IN WEST SUMATRA

<br />The banana weevil, Cosmopolites sordidus Germar, is an important pest of highland banana and plantain in Africa, but it exists in low densities in presumed area of origin in Southeast Asia such as in Indonesia. This suggests a possible existence of effective co-evolved natural enemies in the origin area of Indonesia, especially West Sumatra. The objectives of this study were: (1) to evaluate banana weevil pest status at selected sites in West Sumatra, (2) to survey parasitoids and predators, and (3) to determine the control potential of the most important natural enemies. Surveys were undertaken in March 2002-August 2003 in five locations in West Sumatra, i.e., Bukittinggi, Sitiung, Pariaman, Pasaman, and Batusangkar. Five farms per site were selected randomly among all farms that contained banana stands of > 0.5 ha. Sampling for banana weevil adults and damage, and for predators was done throughout small banana stands and within a 20 m x 40 m (0.08 ha) subplot on larger farms. Field-collected larvae were taken to the laboratory and reared on corm pieces (3 cm x 3 cm x 3 cm) until pupation. Larvae were collected from pseudostem as well as corm residues. To estimate the abundance of non-social predators, i.e., those other than ants, 10 residues each on each farm were examined from plants that had been harvested 1-4 weeks, 5-8 weeks or 9 or more weeks before our visit to the site. Samples of the different morphospecies were saved in alcohol for later identification. The result showed that the banana weevil incidence was found to be low, 0.6-1.7 adults per trap. Plant damage indices were below 2.2%. We collected and reared 24,360 eggs and 3118 larvae, but no parasitism was detected. Phorids (Megaselia sp.) and drosophilids were recovered from larval rearings, but most likely were scavengers. A complex of predators was detected, the most important of which was the histerid beetles, <em>Plaesius javanus </em>Erichson. In laboratory tests, adults and larvae of P. <em>javanus</em> attacked 75-88% and 38-53% of banana weevil larvae and pupae, respectively. Predatory ants, including species of Myrmicinae, Ponerinae, Formicinae, and Dolichoderinae, were found to be associated with banana plants and residues. Adults of Myopopone castanea Smith (Ponerinae) were directly observed attacking banana weevil larvae in crop residues. The adult banana weevil mortalities caused by the entomopathogen fungi of Beauveria bassiana from Baso, Sungaitarab, Sei Sariek, and Sikabau at highest density (3.2 x 108 spores ml-1) after two weeks were 96.67%, 90.00%, 60.00% and 83.33%, respectively. The high diversity of habitat conditions in which crop-pest-natural enemies systems exist, support the idea that banana weevil population and damage intensity in the study area is low due to active role of natural enemies.

Pyrazine emission by a tropical firefly: An example of chemical aposematism?

AbstractAlthough famous for photic courtship displays, fireflies (Coleoptera: Lampyridae) are also notable for emitting strong odors when molested. The identity of volatile emissions and their possible role, along with photic signals, as aposematic warnings of unpalatability have been little explored, especially in tropical species. Pursuant to the observation that the widespread Neotropical fireflies, Photuris trivittata and Bicellonycha amoena, emit pungent odors, glows, and flashes when handled, we investigated their cuticular and headspace chemistry. Gas chromatography–mass spectrometry analyses revealed that both fireflies have species‐specific cuticular hydrocarbon profiles. Photuris trivittata headspace was dominated by 2‐methoxy‐3‐(1‐methylpropyl) pyrazine (hereafter, pyrazine), on the order of 1.59 ng/individual and a suite of sesquiterpenes, while B. amoena emitted 3‐methoxy‐2‐butenoic acid methyl ester and a few ketones. This is the first report of such compounds in fireflies. We investigated the role of pyrazine in P. trivittata's interactions with potential predators: sympatric ants, toads, and bats. Solvent‐washed P. trivittata painted with pyrazine incurred lower ant predation than did their solvent‐washed counterparts. Pyrazine significantly repelled ants at baits in concentrations as low as 9.8 × 10−4 ng/μl. The toad, Rhinella marina, readily accepted intact fireflies, pyrazine‐coated and uncoated mealworms. Both Myotis nigricans and Molossus molossus bats rejected fireflies, but accepted both pyrazine‐coated and uncoated mealworms. While pyrazine repels ants, its role as an aposematic signal warning other potential predators of firefly distastefulness requires further investigation. Our results underscore the idea that multiple enemies exert conflicting selection on firefly defenses.

Haemolymph Defense Capacity of the Neotropical sawfly Aneugmenus merida against Ant Predation

The defensive characteristics of the sawflies have received special attention due to the involvement of toxic compounds obtained from host plants. In this context, the haemolymph-based defense is one of the strategies known in sawflies to dissuade the attack of predators. Aneugmenus merida is a neotropical sawfly whose larvae are herbivorous on the toxic bracken fern Pteridium spp. The present study examines the defensive properties of the A. merida larval haemolymph and its possible link with the chemistry of its host plant. We report the behavior of the solitary hunter ant Odontomachus chelifer towards A. merida larvae under laboratory conditions. In addition, we studied the liquid intake behavior of the ants provided with solutions of crude haemolymph, bracken extracts, and its fractions. A. merida larvae showed a marked defensive capacity against the ants. The inhibition of the attack was observed during the stages of antennal contact and mandibular blow, suggesting that larval defensive capacity is due to factors present in the integument and haemolymph. Aqueous and methanolic fractions of haemolymph and bracken also deterred feeding. Although some common compounds were detected in the haemolymph and bracken fractions, they were in very small quantities, suggesting that they are not responsible for the bioactivity. Therefore, the hypothetical connection between the host plant chemistry and larval defensive capacity could not be evidenced. We suggest that the deterrent compounds present in the haemolymph and integument could be jointly acting in the sawfly’s defensive strategy.