Solenopsis Saevissima Research Articles

The ants of the Galápagos Islands (Hymenoptera, Formicidae): a historical overview, checklist, and identification key.

The Galápagos ant fauna has long been understudied, with the last taxonomic summary being published almost a century ago. Here, a comprehensive and updated overview of the known ant species of the Galápagos Islands is provided with updated species distributions. The list is based on an extensive review of literature, the identification of more than 382,000 specimens deposited in different entomological collections, and recent expeditions to the islands. The ant fauna is composed of five subfamilies (Dolichoderinae, Dorylinae, Formicinae, Myrmicinae, and Ponerinae), 22 genera, 50 species, and 25 subspecies, although three species (Crematogastercrinosa Mayr, 1862, Camponotussenex (Smith, 1858), and Solenopsissaevissima (Smith, 1855)) are considered dubious records. Finally, an illustrated identification key of the species found in the archipelago is presented.

Efficacy and Residual Toxicity of Insecticides on Plutella xylostella and Their Selectivity to the Predator Solenopsis saevissima

We evaluated the efficacy and residual toxicity of nine commercial insecticides on Plutella xylostella and their selectivity to the predator ant Solenopsis saevissima under laboratory and field conditions. First, to test the insecticides' effectiveness and selectivity, we conducted concentration-response bioassays on both species and the mortalities were recorded 48 h after exposure. Next, rapeseed plants were sprayed following label rate recommendations in the field. Finally, insecticide-treated leaves were removed from the field up to 20 days after application and both organisms were exposed to them as in the first experiment. Our concentration-response bioassay indicated that seven insecticides caused mortality ≥80% of P. xylostella: bifenthrin, chlorfenapyr, chlorantraniliprole, cyantraniliprole, indoxacarb, spinetoram, and spinosad. However, only chlorantraniliprole and cyantraniliprole caused mortality ≤30% of S. saevissima. The residual bioassay indicated that four insecticides had a long-lasting effect, causing mortality of 100% to P. xylostella 20 days after application: chlorantraniliprole, cyantraniliprole, spinetoram, and spinosad. For S. saevissima, bifenthrin caused mortality of 100% during the evaluated period. Additionally, mortality rates below 30% occurred four days after the application of spinetoram and spinosad. Thus, chlorantraniliprole and cyantraniliprole are safe options for P. xylostella management since their efficacy favor S. saevissima.

Impact of native vegetation cover near crops on the occurrence and molecular diversity of fire ants

AbstractSolenopsis invicta and Solenopsis saevissima are the most common fire ants in Brazil. Environmental disturbances favour the colony dispersal of both species, particularly those with an anthropogenic origin. However, the frequencies of the species can vary according to the amount of anthropogenic disturbances. Crops near native vegetation fragments is a common landscape in the Brazilian Atlantic Forest. Here, we analyse if there is influence of native vegetation cover on the occurrence of these fire ants and their molecular diversity in crops. Our hypothesis is that these species are antagonistic in terms of occurrence and molecular diversity when compared in the same habitat. We selected crops near fragments with around 50% of native vegetation cover, a percentage informative enough to detect biological responses from insects belonging to a same order. Nests were collected and the species were identified using external morphology, and mtDNA COI sequences. We reject our hypothesis, which suggest that the species colonize the vegetation patches around crops in a similar way. Solenopsis invicta is not limited by vegetation cover, and has a high haplotype diversity when compared to S. saevissima, particularly when the vegetation cover is greater than 50%. Additionally, the vegetation cover seems to not have influence in the total number of haplotypes, but the species have haplotypes that are exclusive to each landscape. Our findings suggest that S. invicta is expanding to native vegetation areas that it has not occupied before, as S. saevissima was dominant there.

Breeding Biology of the Endangered Burrow-Nesting Lesser Crescent-Chested Puffbird Malacoptila minor

For many birds breeding success may be related to the availability of nesting sites, particularly in ecologically specialized cavity-nesting birds. For burrow-nesting species, the selection of an appropriate substrate may be fundamental to a successful breeding attempt. The Lesser Crescent-chested Puffbird Malacoptila minor is a bucconid with a restricted distribution, which is found in the states of Maranhão and Piauí, in northeastern Brazil. It is the only bucconid listed as threatened with extinction, and little is known about its natural history. A total of 49 nests were found over three breeding seasons (2017–2020). Nests consist of burrows dug in the ground that are used only once for breeding. Incubation lasted 21.2 ± 1.3 days and the nestlings fledged after 19.5 ± 2.9 days. The nests contained two or three eggs. The mean hatching rate was 0.46 ± 0.47 eggs per nest and the fecundity rate was 1.0 fledgling per female. The production was 0.53 fledglings per nest, apparent reproductive success was 22.4% (N = 49), and was 15.7% (N = 49) when based on Mayfield's protocol. The probability of breeding success per period was greater during the incubation phase than during the nestling phase. Predation was identified as the principal cause of nest failure (77.5%), mainly during the incubation phase. Three predators were identified: the Crab-eating Fox Cerdocyon thous, the fire ant Solenopsis saevissima, and a lizard, the Common Tegu Salvator merianae. Breeding season starts with the onset of rainy season and nest flooding did not appear to be a concern, which contrasts with the available data on other bucconids. The results of the present study are the first data on the breeding biology of the Lesser Crescent-chested Puffbird, and represent an important advance in the understanding of breeding patterns in the Bucconidae.

Fire ants: What do rural and urban areas show us about occurrence, diversity, and ancestral state reconstruction?

In South America, Solenopsis saevissima and S. invicta are the most common fire ants. Nests are founded in areas under anthropic interference like urban or rural areas, but S. invicta is found preferentially in those with the greatest anthropic interference. However, we do not know the rates at which they exist in anthropized areas next to high density of native vegetation. Areas with 60 to 90% of native Atlantic Forest were selected to verify the occurrence of both species in rural and urban areas. We investigated the molecular diversity and applied the reconstruction of the ancestral state analysis for each species. A total of 186 nests were analyzed and we found that the two species had the same proportion in the urban area. However, S. saevissima had a higher rate of prevalence in the rural area, in addition to having a greater number of haplotypes and ancestry associated with this type of habitat for the region. S. invicta had the same number of haplotypes in both rural and urban regions, and less haplotypic diversity. We conclude that S. saevissima is a species typically associated with rural areas and S. invicta, although present, is not dominant in urban areas.

Life tables for the diamondback moth (Plutella xylostella) in southeast Brazil indicate ants and spiders as leading mortality factors

AbstractThe diamondback moth (DBM), Plutella xylostella (Lep.: Plutellidae), causes significant losses in Brassica crops. Leaf consumption by the larvae reduces plant yield and causes the contamination of heading brassicas. Chemical control usually provides unsatisfactory results due to the quickly developed resistance of DBM populations to insecticides. Thus, natural control by biotic factors (predators, parasitoids, and entomopathogens) is crucial and should be managed upon knowledge of their role as DBM regulators. The leading mortality factors of DBM across the annual seasons in southeast Brazil were investigated by conducting 57 field life tables for 2 years. The highest and lowest total mortalities of DBM occurred in winter (99.7%) and autumn (94%). Predation was the main mortality factor in all seasons. Marginal parasitism rates were higher in spring and lower in autumn, and Oomyzus sokolowskii (Hym.: Eulophidae) accounted for almost 90% of total parasitism. The highest mortalities by rainfall were recorded in spring (44.5%), while physiological death and infection caused low mortalities (≤ 6%) throughout the seasons. In addition, models were built to investigate the main predators acting on the DBM life stages; Araneae, Brachymyrmex bruchi, and Tetramorium simillimum (Hym.: Formicidae) were the predators associated with egg/L1 predation whereas Solenopsis saevissima, T. simillimum and Camponotus spp. (Hym.: Formicidae) were the ones responsible for L4/pupa predation. The L2/L3 stage was the least affected by predation, and the final model for this stage did not include any predator. In light of these findings, habitat manipulation and insecticide selectivity are discussed as measures to preserve the main predators and parasitoid.

A Species delimitation approach to uncover cryptic species in the South American fire ant decapitating flies (Diptera: Phoridae: Pseudacteon).

South American fire ant decapitating flies in the genus Pseudacteon (Diptera: Phoridae) are potential biocontrol agents of the invasive fire ants Solenopsis invicta and S. richteri in the United States and other regions of the world due to their high host specificity and the direct and indirect damage to their host ants. Despite their importance and the fact that several flies have already been released in the US, little is known about the genetic variability and phylogenetic relationships of Pseudacteon flies parasitizing South American fire ants in the Solenopsis saevissima species-group. A species delimitation analysis was conducted using a distance-based method (ABGD) and two tree-based methods (GMYC and mPTP) using COI sequences of 103 specimens belonging to 20 of the 22 Pseudacteon species known from southern South America. Additionally, phylogenetic relationships between the already described and new candidate species were inferred using mitochondrial (COI) and nuclear (wingless) sequences. The species delimitation analysis suggests that species richness in these flies has been previously underestimated, due to the existence of putative cryptic species within nominal Pseudacteon obtusus, P. pradei, P. tricuspis, P. cultellatus, and P. nudicornis. Geographic distribution and host fire ant species seem to support cryptic lineages, though additional morphological data are needed to corroborate these results. All phylogenetic analyses reveal that South American fire ant decapitating flies are grouped into two main clades, with Pseudacteon convexicauda sister and well differentiated relative to these clades. Neither host nor geographic association appeared to be related to the differentiation of these two main clades within South American fire ant decapitating flies. This work provides information that will allow testing whether the putative cryptic phorid fly species show differences in their effectiveness as biocontrol agents against the highly invasive imported fire ants.

Comparisons between different fire ants control methods in urban environments

Many homemade methods are recommended for the control of fire ants, but the choice of a control method for this ants in the urban environment is necessary in view of the damage they have caused to the environment and human health. Thus, the objective of this work was to compare the efficiency of chemical (liquid insecticide and granular insecticide) and homemade (hot water and detergent water) methods used to control these ants in urban gardens. The study was conducted in the city of Juiz de Fora, MG, Brazil. The treatments were applied only once on Solenopsis saevissima colonies: (T1) Hot water, (T2) Water with detergente, (T3) Liquid insecticide and (T4) Granular inseticide. To determine the amount of applied product in T1, T2 and T3 treatments, colonies were selected by linear size and for treatment T4, colonies were classified by volume. the colonies were monitored monthly for four consecutive months (July to October) to evaluate the effectiveness of the control method employed. The treatments presented distinct performances in fire ants control in urban area, being the liquid insecticide the most efficient in eliminating the colonies. With this study we were able to evaluate the impacts caused by each treatment, as well as the pros and cons of using each one of them, and finally, we suggest an efficient fire ants control method with lower cost per colony and less impact on the environment.

Biology of Pseudacteon Decapitating Flies (Diptera: Phoridae) That Parasitize Ants of the Solenopsis saevissima Complex (Hymenoptera: Formicidae) in South America.

Pseudacteon flies (Diptera: Phoridae) parasitize individual ant workers, causing decapitation of the host during pupariation. Phorid flies that attack South American fire ants in the Solenopsis saevissima (Smith) complex are distributed across a wide range of habitats and climates associated with the geographical range of their hosts. Sympatric species sharing the same hosts often partition niche resources by season, active time of day, host size, and/or different host activities. They have the potential of being used for biological control of the imported fire ants in North America, Australia, and Asia.

Toxicity of Piperine Amide Analogs toward the Tomato Pinworm Tuta absoluta (Lepidoptera: Gelechiidae) and Risk Assessment for Two Predators

Nineteen amides (three of them unpublished) were synthesized and tested on Tuta absoluta Meyrick (Lepidoptera: Gelechiidae), an important pest of Solanaceae plants worldwide. Three of these compounds (14, 15 and 16) presented high acute toxicity toward the pest, with LD50s of 3.68 (CI95 = 2.83 − 4.47), 6.46 (CI95 = 5.85 − 7.20), and 13.52 μg/mg (CI95 = 11.06 − 15.95), respectively. Amide 14 presented the fastest action (LT50 = 1.2 minutes, CI95 = 1.03 − 1.37), followed by amide 16 (LT50 = 18 minutes, CI95 = 9.96 − 26.04), and amide 15 (LT50 = 3.7 hours, CI95 = 0.69 − 6.71). When applied at a sublethal dose, they did not affect weight gain and leaf consumption of the pest. Bioassays were also conducted using the ant Solenopsis saevissima (Hymenoptera: Formicidae) and wasp Polybia ignobilis (Hymenoptera: Vespidae) to assess the toxicity of the amides against T. absoluta predators. Amides 14, 15, and 16 were harmless to S. saevissima but presented high toxicity toward P. ignobilis. Amides 14, 15 and 16 are potential hit compounds for the development of insecticides for T. absoluta control. However, their use should be carried out following the principles of ecological selectivity to mitigate potential adverse effects on non-target organisms.

Stenochrus portoricensis (Arachnida: Schizomida) living in a nest of the fire ant Solenopsis saevissima (Hymenoptera: Formicidae) in the Atlantic Forest, Brazil

Schizomida is an arachnid order widely distributed in tropical and subtropical regions, commonly found in humid and warm environments such as leaf litter, on the underside of rocks, and in caves. Stenochrus portoricensis has been observed in association with termite and ant nests. In this study, we report for the first time S. portoricensis living within a nest of the fire ant Solenopsis saevissima. This new interaction triggers interest in the mechanisms used by the schizomid to deceive and be undetected by fire ants, as well as the potential advantages for the schizomid in living within Solenopsis nests.

Actions of the Fire Ant Solenopsis saevissima (Smith) (Hymenoptera: Formicidae) on a Big-Eared Opossum Carcass

We described the effects of fire ants (Solenopsis saevissima) (Hymenoptera: Formicidae) on and in a big-eared opossum (Mammalia: Marsupialia: Dedelphidae) carcass. The observations were made in southeastern Brazil beside of a public highway. We documented the competitive ability of the fire ants, which sought to reduce competition with necrophagous flies by constructing a soil structure over the natural orifices of the carcass. After we removed the structure, the ants changed their physical and ecological behavior on the carcass until the end of decomposition. This ant behavior of blocking access to the carcass delays the decomposition process due to the fact that other necrophagous insects cannot forage there.

Bioactivity of essential oils from Artemisia against Diaphania hyalinata and its selectivity to beneficial insects

ABSTRACT: The demand for effective insecticides in pest control with low toxicity to the non-target organisms, such as natural enemies and pollinators, is increasing steadily. A good alternative for synthetic insecticides is natural compounds, including essential oils (EO). This work assessed toxicity of essential oils extracted from Artemisia annua, A. absinthium, A. camphorata, A. dracunculus and A. vulgaris against the melonworm Diaphania hyalinata (Linnaeus, 1758) (Lepidoptera: Crambidae) larvae, a pest of Cucurbitaceae, and their selectivity for fire ant Solenopsis saevissima (Smith) (Hymenoptera: Formicidae) and jatai bee Tetragonisca angustula (Latreille) (Meliponinae). The plants were grown in a greenhouse with mineral fertilization and were used for EO extraction. The insects in the bioassay belonged to the second instar of D. hyalinata and adult forms of S. saevissima and T. angustula. Essential oil from A. annua induced a high mortality rate in D. hyalinata (96 %) over a 48 h period. The same essential oil was selective for predator S. saevissima (42 % mortality) and pollinator T. angustula (74 % mortality), while causing high mortality in D. hyalinata. The insecticidal activity of A. annua oil was attributed to the synergism of its constituents viz., camphor and 1,8-cineole. Therefore, this essential oil contains constituents that are promising for effective use as insecticide due to its high toxicity and rapid action against D. hyalinata as well as low toxicity for predator and pollinator.

INSECTICIDAL ACTIVITY OF DIENAMIDES ON CABBAGE CATERPILLAR AND BENEFICIAL INSECTS

The demand for new insecticides is increasing due to the appearance of insect populations that are resistant to currently used products. New insecticides should be efficient in controlling pests and present low toxicity to non-target organisms. Ascia monuste (Lepidoptera: Pieridae) is a destructive pest of cole vegetables, and the fire ant Solenopsis saevissima (Hymenoptera: Formicidae) is an important predator of these caterpillars in brassica crops. Tetragonisca angustula (Hymenoptera: Apidae) is very important in pollinating many plants and providing honey. Therefore, this study evaluated the toxicity of synthetic amides to A. monuste and its selectivity in favor of S. saevissima and T. angustula. The amides (2E,4E)-N-propylhexa-2,4-dienamide (3) and (2E, 4E)-N-butylhexa-2,4-dienamide (4) caused high (96 and 93%, respectively) and fast (48 h) mortality of A. monuste. The amides 3 and 4 were not harmful to the predator (mortality of 5.7% for amide 3 and 7.14% for amide 4) and were slightly harmful to the pollinator (mortality of 38.57% for amide 3 and 28.12% for amide 4). The amides 3 and 4 are promising, as insecticides, due to the high and rapid mortality of A. monuste with low and moderate toxicity to S. saevissima and T. angustula, respectively.

Phthalides as promising insecticides against Tuta absoluta (Lepidoptera: Gelechiidae)

ABSTRACTIn this study, the insecticide potential of eight phthalides derived from furan-2(5H)-one was evaluated against Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) larvae. The potency of the most active phthalides and the susceptibility of six different T. absoluta populations to these compounds were determined. The toxicity of these molecules to two non-target species (Solenopsis saevissima Smith and Tetragonisca angustula Latreille) was also evaluated. Two phthalides (3 and 4) presented insecticide potential against T. absoluta. Phthalide 4 was as toxic as piperine (positive control) and both phthalides exhibited rapid action (LT50 < 2 hours). The variation in the susceptibility of T. absoluta populations to the phthalides 3 and 4 was low. Neither phthalide presented physiological selectivity for non-target species.Therefore, the phthalides 3 and 4 are promising molecules, or at least, a starting point for a chemical optimization program leading to formulations for the management of the tomato leafminer. The application of such products should be conducted according to the principles of ecological selectivity.

Pseudacteon Phorid Flies: Host Specificity and Impacts on Solenopsis Fire Ants.

Human commerce has resulted in the spread of the imported fire ants, Solenopsis species, worldwide. Six species of parasitic Pseudacteon phorid flies that are highly host specific to the Solenopsis saevissima complex of Solenopsis fire ants have been successfully released in the southern United States. The presence of Pseudacteon phorid flies, in addition to having direct mortality effects on their host ants, modifies foraging behavior and disrupts interspecific competition between host species and other ant species in the community. Fire ant workers have evolved effective methods to cope with parasitism pressure, which may relieve population-level impacts of introduced phorid flies. This review focuses on the mechanisms underlying host location, host preference, and host-size selection of Pseudacteon phorid flies and highlights their direct and indirect effects on fire ant populations. Knowledge gained from parasitoid-ant interactions will enhance use of natural enemies as biological control agents for invasive social insects.

Corymbia spp. and Eucalyptus spp. essential oils have insecticidal activity against Plutella xylostella

Plutella xylostella (L.) is the main brassica pest worldwide and is difficult to control even with commercial insecticides. In this study, assessments were made of the contact toxicity of essential oils (EOs) from ten Myrtaceae species. For this, the leaves of four Corymbia species (C. citriodora, C. intermedia, C. maculata, and C. ptychocarpa) and six Eucalyptus species (E. andrewsii, E. crebra, E. punctata, E. pyrocarpa, E. siderophloia, and E. sphaerocarpa) were collected during the Brazilian dry season and subjected to hydrodistillation for extraction of EOs. For C. citriodora, another sample was also collected during the rainy season. The essential oil (EO) content of all samples ranged from 0.07% w/w to 3.3% w/w and GC–MS analyses allowed the identification of 52 compounds. For E. andrewsii, E. pyrocarpa, and C. ptychocarpa there was no previous report on EO chemical composition. For C. citriodora, a higher EO content for the samples collected during the dry season was found (2.72% versus 1.53% for the rainy season). The insecticidal activity of all eleven EOs was evaluated via topical application on the second-instar larvae of P. xylostella. The most active EOs were produced by C. citriodora collected during the dry season, with citronellal (86.8%) and isopulegol (4.7%) being the main constituents. At 30μg/mg of insect, these EOs caused 80% P. xylostella mortality, being more active than neem oil used as positive control. These EOs presented low toxicity for Solenopsis saevissima, a natural predator of P. xylostella. Bioassays also demonstrated a synergistic effect between citronellal and (-)-isopulegol at all tested proportions. The results described here suggest that C. citriodora EOs can be an environmentally friendly alternative method to control P. xylostella.

Selection of an essential oil from Corymbia and Eucalyptus plants against Ascia monuste and its selectivity to two non-target organisms

Due to an increase in environmental and health issues and with the excessive use of synthetic pesticides, many studies are investigating plant essential oils (EOs) for pest control. These compounds are considered safe control agents since they have low toxicity to non-target organisms. Thus, this study aimed to select potential EOs from the Myrtaceae family and their constituents for the control of Ascia monuste (Godart) and to evaluate those EOs selectivity to two non-target organisms (Solenopsis saevissima Smith and Tetragonisca angustula Latreille). Twelve EOs, extracted by hydrodistillation from Corymbia and Eucalyptus plants, were tested in this study. All toxicity bioassays were performed by topical application. C. citriodora EO had the highest insecticidal activity against A. monuste (LD50 = 20.61 μg/mg) and also presented a fast action (LT50 < 10 min). Citronellal was the main compound of C. citriodora EO (86.8% of the oil constitution) and exhibited toxicity similar to this EO. The other compounds caused no significant mortality. Hence, the toxicity of the C. citriodora EO is mostly explained by the citronellal activity. This EO was selective in favor of the predatory ant S. saevissima but caused high mortality of the pollinator bee T. angustula. Therefore, C. citriodora EO is a promising model in the development of insecticides against A. monuste. However, to mitigate its impact over pollinators, its application must rely on the principles of ecological selectivity.

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.

Larvicidal activity of synthetic tropane alkaloids against Ascia monuste orseis (Lepidoptera: Pieridae).

Tropane alkaloids are known to play a role in plant defence. By blocking acetylcholine receptors, they exert insecticidal and deterrent effects against herbivore insects. Carbamates are an important class of chemical insecticides that also inhibit acetyl cholinesterase. The objective of this work was to synthesise a series of tropane alkaloids bearing a carbamate group, and to evaluate their effects against the pest Ascia monuste. The effects of the most active compounds were evaluated on the A. monuste predator Solenopsis saevissima and on the pollinator Tetragonisca angustula. The synthesis of carbamate-tropane alkaloids was accomplished in 4-5 steps from commercially available ketones. Results from bioassays showed that compounds 6a, 10a and 14a presented higher activities against second-instar larvae of A. monuste, with LD50 values of 1.01, 3.76 and 1.92 µg substance mg-1 insect, and TL50 values of 7.0, 15.0 and 5.0 h respectively. These compounds were also tested for their selectivity in favour of S. saevissima and T. angustula. Compound 6a, which showed the highest activity against A. monuste, also showed lower toxicity against S. saevissima. Tropane alkaloid derivatives bearing a carbamate group show potential for the development of novel insecticides against A. monuste. © 2017 Society of Chemical Industry.