Little fire ants

In the fire ant Solenopsis invicta, a supergene composed of ~ 600 genes and having two variants, SB and Sb, regulates colony social form. In single queen colonies all individuals carry only the SB allele, while in multiple queen colonies, some individuals carry the Sb allele. In this study we characterized genes with copy number variation between SB and Sb-carrying individuals. We showed extensive acquisition of gene duplicates in the Sb genome, with some likely involved in polygyne-related phenotypes. We found 260 genes with copy number differences between SB and Sb, of which 239 have greater copy number in Sb...

Body size is an important life-history trait in eusocial insects which plays a key role in colony fitness. The division of labour, represented by caste polyethism, correlates with divergent morphological traits. Size polymorphism has been noted in the tropical fire ant, Solenopsis geminata; however, little is known regarding the differences in the size distributions of workers performing foraging tasks. In the present study, task partitioning was observed in the foraging activities of S. geminata. Two subgroups among foraging workers of S...

PURPOSE: To describe the ocular findings and the long-term outcomes of patients diagnosed with corneal injury due to little fire ants (LFAs). METHODS: This is a retrospective case series of patients evaluated with corneal injury due to LFAs from October 2015 to January 2018 at the Cornea Clinic in Meir Medical Center. Patients underwent anterior segment optical coherence tomography (AS-OCT) imaging during the follow-up. RESULTS: Four patients reported ocular contact with LFAs and presented to our department with unilateral, scattered, small, dense, round, bright white opacities in the anterior corneal stroma, which remained unchanged in appearance over time, despite topical antibiotic and steroid treatment...

Recent increases in the frequency and size of desert wildfires bring into question the impacts of fire on desert invertebrate communities. Furthermore, consumer communities can strongly impact invertebrates through predation and top-down effects on plant community assembly. We experimentally applied burn and rodent exclusion treatments in a full factorial design at sites in both the Mojave and Great Basin deserts to examine the impact that fire and rodent consumers have on invertebrate communities. Pitfall traps were used to survey invertebrates from April through September 2016 to determine changes in abundance, richness, and diversity of invertebrate communities in response to fire and rodent treatments...

Encouraging motivated landowners to not only engage in conservation action on their own property but also to recruit others may enhance effectiveness of conservation on private lands. Landowners may only engage in such recruitment if they believe their neighbors care about the conservation issue, will positively respond to their conservation efforts, and are likely to take action for the conservation cause. We designed a series of microinterventions that can be added to community meetings to change these beliefs to encourage landowner engagement in recruitment of others...

Fire ant venom contains insecticidal alkaloids named 'solenopsins'. Whilst species-specific differences are reported, little attention has been given to caste-specific venom adaptations. The venom of fire ant queens has remained particularly poorly studied, though studies have shown it to be strikingly similar across different species, in being primarily composed of the alkaloid isosolenopsin A, regardless of the chemical configuration in workers. We predict that this is the evolutionary outcome of stabilising selection, implying that a shared mechanism is responsible for the conserved venom composition among fire ant queens...

The little fire ant Wasmannia auropunctata, native to the Neotropics, has become a serious pest worldwide over the past 100 years. It was originally distributed from Mexico to northern Argentina and new evidence suggests a recent southern range expansion during the last 60 years reaching central Argentina. This supercolonial ant species has a polymorphic reproductive system. Some populations, mostly found in undisturbed natural environments, are characterised by a classical sexual haplodiploid reproductive system...

Fire is a major driver in many ecosystems. Yet, little is known about how different ground-living arthropods survive fire. Using three sampling methods, and time-since-fire (last fire event: 3 months, 1 year, and 7 years), we investigate how ground-living arthropod diversity responds to fire, and how species richness, diversity, abundance, and composition of the four dominant taxa: ants, beetles, cockroaches and mites, respond. We did this in the naturally fire-prone Mediterranean-type scrubland vegetation (fynbos) of the Cape Floristic Region...

Molecular cross-reactivity caused by allergen homology or cross-reactive carbohydrate determinants (CCDs) is a major challenge for diagnosis and immunotherapy of insect venom allergy. Venom phospholipases A1 (PLA1s) are classical, mostly non-glycosylated wasp and ant allergens that provide diagnostic benefit for differentiation of genuine sensitizations from cross-reactivity. As CCD-free molecules, venom PLA1s are not causative for CCD-based cross-reactivity. Little is known however about the protein-based cross-reactivity of PLA1 within vespid species...

Headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) is commonly used in analyzing insect volatiles. To improve the detection of volatiles in insects, a freeze-thaw method was applied to insect samples before the HS-SPME-GC-MS analysis. Insect samples were first frozen at -80 °C for 10 min and then thawed at 25 °C for 5 min before SPME extraction was performed. The freeze-thaw method clearly improved the detection of volatile compounds for all six tested insect species, including red imported fire ants, Solenopsis invicta Buren, black imported fire ants, Solenopsis richteri Forel, little black ants, Monomorium minimum (Buckley), pharaoh ants, Monomorium pharaonis (Linnaeus), eastern subterranean termites, Reticulitermes flavipes (Kollar), and spotted lady beetles, Coleomegilla maculate De Geer...

Fire is one of the most relevant ecological disturbances in nature. Little is known about the effects of fire on biodiversity in ecosystems like rupestrian grasslands, which share characteristics with savanna and forest biomes. Brazilian rupestrian grasslands are part of an endangered ecosystem that has been modified by anthropogenic fire events that have become more intense in recent decades. In this study, we evaluated the effects of fire on ground and arboreal ant assemblages through a two-year monitoring program (24 monthly samplings)...

Necrophoric behavior is essential to colony health in social insects. Little is known about the genes that are responsible for necrophoric behavior. Here, we show that a chemosensory protein gene Si-CSP1 was expressed significantly higher in the antennae than in other tissues such as the legs and heads of Solenopsis invicta Buren workers. Furthermore, Si-CSP1-silenced workers moved significantly fewer corpses of their nestmates than normal workers. Finally, Si-CSP1-silenced workers exhibited weaker antennal responses to oleic acid and linoleic acid than controls...

The red imported fire ant, Solenopsis invicta (Buren), left most of its natural enemies behind in South America when it arrived in Mobile, AL, in the 1930s and spread rapidly throughout the southeastern United States, reaching population levels up to 10 times those found in South America. The large population densities and propensity for disturbed habitats led to direct conflict with human activities. Bait control methods were first developed for fire ants in the early 1960s and little has changed in the subsequent decades, despite the drawback that the bait carrier rapidly breaks down when wet...

Variation in social behaviour is common, yet little is known about the genetic architectures underpinning its evolution. A rare exception is in the fire ant Solenopsis invicta: Alternative variants of a supergene region determine whether a colony will have exactly one or up to dozens of queens. The two variants of this region are carried by a pair of 'social chromosomes', SB and Sb, which resemble a pair of sex chromosomes. Recombination is suppressed between the two chromosomes in the supergene region. While the X-like SB can recombine with itself in SB/SB queens, recombination is effectively absent in the Y-like Sb because Sb/Sb queens die before reproducing...

Many previous studies have focused on the foraging behaviors and strategies of the red imported fire ants, Solenopsis invicta Buren on solid food or granular bait; little attention has been paid to how liquid sugar is fed upon. In the present study, behavioral responses of S. invicta to 25% sucrose water droplets were observed. Five foraging patterns were identified in S. invicta colonies under laboratory conditions: (i) no feeding, no sucrose water feeding was observed; (ii) surround feeding, ants surrounded and fed along the edge of the sucrose droplet; (iii) stacked feeding, ants stacked and fed along the edge of the sucrose droplet; (iv) droplet-break feeding, ants broke the liquid droplet and sucked sucrose water that spread on surface of the substance or soil particles previously transported by ants; and (v) cover feeding, whole surface of the sucrose droplet was covered by layers of feeding ants...

The evolutionary history of invasive species within their native range may involve key processes that allow them to colonize new habitats. Therefore, phylogeographic studies of invasive species within their native ranges are useful to understand invasion biology in an evolutionary context. Here we integrated classical and Bayesian phylogeographic methods using mitochondrial and nuclear DNA markers with a palaeodistribution modelling approach, to infer the phylogeographic history of the invasive ant Wasmannia auropunctata across its native distribution in South America...

Red imported fire ants, Solenopsis invicta, are significant invasive pests. Certain native ant species can compete with S. invicta, such as the little black ant, Monomorium minimum. Defensive secretions may contribute to the competition capacity of native ants. The chemistry of ant defensive secretions in the genus Monomorium has been subjected to extensive research. The insecticidal alkaloids, 2,5-dialkyl-pyrrolidines and 2,5-dialkyl-pyrrolines have been reported to dominate the venom of M. minimum. In this study, analysis of defensive secretions of workers and queens of M...

Evolution of reproduction strategies is affected by both phylogenetic and physiological constraints. Although clonality may benefit females, it may not be selected if a male contribution is necessary to start egg laying and embryo development. In little fire ant, Wasmannia auropunctata, sexual populations employ a typical Hymenopteran system of reproduction. In clonal populations, however, queens and males are produced with only maternal and paternal genomes, respectively, whereas sterile workers are produced sexually...

BACKGROUND: Cogongrass (Imperata cylindrica Beav.) is an aggressive, invasive weed with a global distribution. In North America, it threatens the integrity of southeastern pine agroecosystems, including longleaf pine (Pinus palustris Mill.). While studies have examined the impacts of cogongrass and various vegetation management strategies on longleaf pine understory plant communities, little is known about how they impact associated insect communities. To understand the effect of cogongrass management strategies on arthropod natural enemies and bark beetles, a split-plot design was used to test fire (whole-plot) and four subplot treatments (control, herbicide, seeding and herbicide plus seeding)...

The little fire ant, Wasmannia auropunctata (Roger) (Hymenoptera: Formicidae), is an invasive ant with negative impacts on both biodiversity and agriculture throughout the tropics and subtropics. Field experiments were conducted in order to elucidate the relative attractiveness of the enantiomers of the alarm pheromones, 2,5-dimethyl-3-(2-methylbutyl)pyrazine and 3-methyl-2-(2-methylbutyl)pyrazine. The enantiomers tested were synthesized from commercially available (S)-2-methylbutan-1-ol or kinetically resolved (R)-2-methylbutan-1-ol, prepared using Pseudomonas cepacia lipase (PCL)...