Search Results (51)

Background: Solenopsis invicta, commonly known as the red imported fire ant (RIFA), is an important global invasive pest, and its management is challenging because of insecticide resistance and environmental problems. Methods: In this research, we applied transcriptomics to analyze the molecular responses of S. invicta worker ants exposed to different types of pesticides, beta-cypermethrin (BC) and the entomopathogenic fungus Cordyceps cicadae (CC), as well as to different concentrations of these pesticides. Results: A total of 2727 differentially expressed genes (DEGs) were identified across all samples. The number of DEGs in the BC treatment group was significantly higher than that in the CC treatment group (2520 vs. 433), and higher concentrations resulted in more DEGs (an increase of 47 in the BC group and 229 in the CC group). KEGG pathway analysis revealed that the DEGs were significantly enriched in lipid metabolism, carbohydrate metabolism, amino acid metabolism, signal transduction, and membrane transport. Immune-related gene analysis showed more general down-regulation (average FPKM value in BC 741.37 to 756.06 vs. CK 1914.42) of pathogen recognition genes (PGRP-SC2) under BC stress conditions, while CC treatment resulted in increases in expression of important immune effectors such as various serine proteases. Conclusions: Overall, this study provides useful insights into the molecular basis of responses to different pesticides in S. invicta and offers a basis to develop new approaches to control this pest. Full article

Background and Clinical Significance: Hell’s Itch is a rare, intensely uncomfortable post-sunburn condition with burning pruritus emerging 24–72 h after UV exposure. This condition often goes unrecognized and is frequently misdiagnosed by healthcare providers due to a lack of knowledge and familiarity. Standard antipruritic measures are often ineffective, and patients frequently rely on anecdotal self-management. Case Presentation: Three healthy adult males between 23 and 28 years old experienced multiple episodes of delayed-onset intense pruritus following moderate-to-severe sun exposure. The patients experienced a burning or stinging pain which they described as “fire ants” or “thumbtacks,“ and their symptoms started between 24 and 72 h after sun exposure without any rash or fever symptoms. The patients did not achieve symptom relief from standard treatments which included oral antihistamines and topical lidocaine, NSAIDs, aloe vera, and cold compresses. The patients received β-alanine treatment through pre-workout supplements or pure powder after consulting non-clinical sources. Each patient ingested β-alanine and reported rapid relief (itch 8–10/10 → 1–2/10) lasting 2–3 h. The only adverse effect reported by one patient was mild paresthesia. Conclusions: This case introduces β-alanine as a potential off-label therapy for Hell’s Itch and emphasizes the psychological burden and clinical complexity of the condition. While anecdotal, further study is needed to elucidate the mechanism of action of β-alanine in relieving symptoms of Hell’s Itch, as well as assess safety and efficacy in controlled settings. Increased clinical awareness of Hell’s Itch may reduce patient distress and improve management strategies. Full article

While foraging tunnels of the red imported fire ant, Solenopsis invicta, have been well studied, much less is known about the tunnels constructed between neighboring nests, despite their perceived importance in intra-colony exchange and collaboration. In this study, we investigated such tunnels by excavating 80 pairs of nests (with distances of <1 m between nests) located in different types of habitats. For each pair of nests, we recorded the number of inter-nest tunnels and observed their shape, diameter, subsurface depth, and ant presence within them. Moreover, we analyzed the relationships between the probability of constructing inter-nest tunnels and several nest/habitat characteristics, including distance between nests, colony social form, nest size, soil type, and vegetation cover, as well as the relationships between tunnel numbers and these factors. The results show that the number of inter-nest tunnels ranges from one to 11. These tunnels open to the two nests at terminals, are elliptical in cross-section, <1.5 cm in diameter, and mostly at 1–3 cm (range 1–12 cm) subsurface depth. Among the 36 pairs of nests possessing tunnels, 31 pairs (86.1%) had worker or alate ants within their tunnels. Polygynous colonies are more likely (52.4%) to construct inter-nest tunnels than monogynous colonies (17.6%). Nest pairs that have a small nest, located in habitats with higher vegetation cover and loamy or sandy loam soil, tend to have inter-nest tunnels. We also showed that the capacity of constructing inter-nest tunnels falls in the regime similar to foraging tunnels. As nests were treated with chemicals, 33 nests were relocated and 47 new nests resulted within 2 weeks, but no definite tunnels were constructed between original nests and corresponding new nests. Our results highlight the significance of including such tunnels when analyzing intra-colony exchange, collaboration, and adaptive strategies in S. invicta. Uses of tunnels by fire ants during nest relocation, and the requirement of destroying them during control program implementation, were discussed. Full article

The red imported fire ant (RIFA; Solenopsis invicta) is an invasive species that severely threatens ecology, agriculture, and public health in Taiwan. In this study, the feasibility of applying multispectral imagery captured by unmanned aerial vehicles (UAVs) to detect red fire ant mounds was evaluated in Fenlin Township, Hualien, Taiwan. A DJI Phantom 4 multispectral drone collected reflectance in five bands (blue, green, red, red-edge, and near-infrared), derived indices (normalized difference vegetation index, NDVI, soil-adjusted vegetation index, SAVI, and photochemical pigment reflectance index, PPR), and textural features. According to analysis of variance F-scores and random forest recursive feature elimination, vegetation indices and spectral features (e.g., NDVI, NIR, SAVI, and PPR) were the most significant predictors of ecological characteristics such as vegetation density and soil visibility. Texture features exhibited moderate importance and the potential to capture intricate spatial patterns in nonlinear models. Despite limitations in the analytics, including trade-offs related to flight height and environmental variability, the study findings suggest that UAVs are an inexpensive, high-precision means of obtaining multispectral data for RIFA monitoring. These findings can be used to develop efficient mass-detection protocols for integrated pest control, with broader implications for invasive species monitoring. Full article

The red imported fire ant (Solenopsis invicta) is a dangerous invasive insect. These ants rely on releasing an alarm pheromone, mainly composed of 2-ethyl-3,6-dimethylptrazine (EDMP), to warn nestmates of danger and trigger group defense or escape behaviors. This study found two NPC2 proteins in the ant antennae: SinvNPC2a and SinvNPC2b. SinvNPC2a was highly expressed in the antennae; phylogenetic analysis also suggests that SinvNPC2 likely possesses conserved olfactory recognition functions. By knocking down the SinvNPC2a gene, we found that the electrophysiological response of ant antennae to EDMP became weaker. More importantly, ants lacking SinvNPC2a showed significantly reduced movement range and speed when exposed to EDMP, compared to normal ants not treated with RNAi. These ants did not spread out quickly. Furthermore, tests showed that the purified SinvNPC2a protein could directly bind to EDMP molecules. Computer modeling also showed that they fit together tightly. These findings provide direct evidence that the SinvNPC2a protein plays a key role in helping fire ants detect the EDMP alarm pheromone. It enables the ants to sense this chemical signal, allowing ant colonies to respond quickly. Understanding this mechanism improves our knowledge of how insects smell things. It also suggests a potential molecular target for developing new methods to control fire ants, such as using RNAi to block its function. Full article

We evaluated the effects of different fire regimes on the ground-ant community from a savanna (Cerrado) reserve in southern Brazil, where a process of woody encroachment has been taking place. Ants are a dominant faunal group in tropical savannas. Over ~8 years, experimental plots were protected from fire or burned every one or two years. An additional treatment (adaptive) included annual fires and a reduction in woody biomass to increase fuel loads. Ants were collected prior to the first prescribed fire and again four times. We expected that fire would increase the diversity and overall abundance of open-savanna ant specialists, depending on the extent of changes in vegetation structure. Changes in litter depth, grass cover and bare ground in burned plots were most evident 88 months after the first fire and did not differ between fire regimes. Similarly, overall ant species richness and occurrence neither differed between fire treatments nor from the control. However, burned plots showed a significant increase in the richness and occurrence of open savanna specialists, and a decrease in species most typical of dense savanna or dry forests. As ant responses did not differ between the annual, biennial, and adaptive treatments, we suggest that a fire return interval of two years is enough for reverting the loss of open savanna ant specialists in areas that have been protected from fire for decades. Full article

Bioinsecticides based on the bacterium Bacillus thuringiensis (Bt) are widely used as safe alternatives to chemical insecticides. The insecticidal activity of Bt is occasioned by a protein toxin contained in parasporal crystals (Cry proteins) that are synthesized and laid down alongside the endospore during sporulation. The specificity of toxin action is associated with the subspecies of Bt and the individual Cry toxins they produce. Although a number of commercial Bt formulations are available to control moths, mosquitoes and beetles, there are none that control the red imported fire ant (RIFA) Solenopsis invicta. The present report is the first to describe the insecticidal activity of the Cry3A protein toxin, produced by Bacillus thuringiensis subsp. tenebrionis (Btt), against the RIFA as well as some of its key biochemical properties. Currently available commercial formulations of Btt are designed to control beetles such as the Colorado potato beetle, not ants. The Cry3A toxin (MW ~66 kDa) is embedded in a larger polypeptide (protoxin, MW ~73 kDa) and is released from the toxin enzymatically. Once activated, it can be administered to the RIFA as a soluble protein that most likely binds to an attendant receptor in the epithelial cells that line the wall of the larval ventriculus, killing the insect. Properly customized, the Cry3A toxin is a potential candidate for fire ant control. Full article

Piper crassinervium Kunth (Piperaceae) essential oil (EO) was evaluated for its toxicity and repellency against red imported fire ants (RIFA), Solenopsis invicta Buren, and a hybrid (HIFA) of red (S. invicta) and black (S. richteri Forel) imported fire ants. Through bioactivity-guided fractionation, two major components, elemicin and myristicin, were isolated from the EO. Removal of treated sand in a digging bioassay was used as the criterion for repellency. The EO showed significantly higher repellency at concentrations of 7.8 µg/g against RIFA and HIFA workers, as compared to the DEET (N,N-diethyl-meta-toluamide) or ethanol control. Elemicin exhibited repellency at 3.9 and 7.8 µg/g against RIFA and HIFA workers, respectively, whereas myristicin was active at 7.8 µg/g against both species. DEET failed at 31.25 µg/g against RIFA and 15.6 µg/g against HIFA. The EO showed LC₅₀ values of 97.9 and 73.7 µg/g against RIFA and HIFA workers, respectively. Myristicin was more toxic against RIFA and HIFA with LC₅₀ values of 54.3 and 35.3 µg/g, respectively. Elemicin showed 20–40% mortality at the highest screening dose of 125 µg/g. Fipronil exhibited the highest toxicity against RIFA and HIFA, with LC₅₀ of 0.43 and 0.51 µg/g, respectively. Different formulations of these natural products should be evaluated to explore their use potential under natural field conditions. Full article

Peptidoglycan recognition proteins (PGRPs) are a class of pattern recognition receptors (PRRs) that activate the innate immune system in response to microbial infection by detection of peptidoglycan, a distinct component of bacterial cell walls. Bioinformatic studies have revealed four PGRPs in the red imported fire ant Solenopsis invicta; nonetheless, the mechanism of the immune response of S. invicta induced by pathogens is still poorly understood. The peptidoglycan recognition protein full-length cDNA (designated as SiPGRP-S1/S2/S3/L) from S. invicta was used in this investigation. According to the sequencing analysis, there was a significant degree of homology between the anticipated amino acid sequence of SiPGRPs and other members of the PGRPs superfamily. Molecular docking studies demonstrated that SiPGRPs show strong binding affinity for a variety of PGN substrates. Additionally, tissue distribution analysis indicated that SiPGRPs are primarily expressed in several tissues of naïve larvae, including fat body, hemocytes, head, and thorax, as detected by quantitative real-time PCR (RT-qPCR). Microbial challenges resulted in variable changes in mRNA levels across different tissues. Furthermore, the antibacterial effects of antimicrobial peptides (AMPs) produced by major ants infected with Metarhizium anisopliae were assessed. These AMPs demonstrated inhibitory effects against M. anisopliae, Staphylococcus aureus, and Escherichia coli, with the most pronounced effect observed against E. coli. In conclusion, SiPGRPs act as pattern recognition receptors (PRRs) that identify pathogens and initiate the expression of AMPs in S. invicta, this mechanism contributes to the development of biopesticides designed for the targeted control of invasive agricultural pests. Full article

The red imported fire ant (RIFA, Solenopsis invicta Buren) represents a significant invasive pest in China, exerting extensive negative impacts on ecosystems. The invasion of RIFA not only poses a severe threat to biodiversity within the environment; inappropriate controlling measures can also adversely affect community dynamics. Therefore, while implementing effective management strategies to control the proliferation of RIFA populations, it is imperative to evaluate the potential effects of these measures on the structure of local biological communities to safeguard native biodiversity. This study employs a “two-step method” using dust and bait formulations, respectively, to control RIFA while conducting ecological monitoring to further assess the impact of RIFA population decline on ant communities. The results of RIFA management showed that after post-treatment periods of 28 days, 35 days, and 60 days, the worker ant reduction rates for the three insecticides—0.5% beta-cypermethrin dust, 1.0% hydramethylnon bait, and 0.1% indoxacarb bait—reached approximately 72%, with their efficacy ranked as follows: 1.0% hydramethylnon bait > 0.1% indoxacarb bait > 0.5% beta-cypermethrin dust. By the 60th day of the experiment, the ant nest reduction rates reached their highest values—66.84% for 0.5% beta-cypermethrin dust, 77.89% for 1.0% hydramethylnon bait, and 87.52% for 0.1% indoxacarb bait—with the latter performing the best. Meanwhile, the occurrence level of RIFAs in all three pesticide treatment areas decreased from level III to level I 60 days post-treatment. Following the application of these three insecticides, the RIFA population significantly decreased, leading to an increase in species richness within the ant community. The reduction in RIFA numbers had a positive impact on the restoration of ant community diversity, as evidenced by significant improvements in both diversity and evenness indices. Notably, 0.1% indoxacarb bait was particularly effective in enhancing the ant community diversity and species richness, while 1.0% hydramethylnon bait was more effective in improving community evenness. These findings indicate that the controlling strategy used in this study not only effectively manages RIFA populations but also promotes recovery and contributes to the ecological balance of local ant communities, providing an important reference for future biodiversity conservation efforts. Full article

Imported fire ants are pests of significant importance, especially in the southern United States. We tested (E/Z)-3-butylidenephthalide, a natural compound that was isolated from the ethanolic extract of Ligusticum porteri roots, as a repellent and toxicant against workers of imported fire ants. A series of serial concentrations, starting from 156 µg/g until failure, were tested using digging bioassays. Workers removed significantly less sand from the vials treated with (E/Z)-3-butylidenephthalide as compared to the ethanol control. Based on sand removal data, (E/Z)-3-butylidenephthalide treatment resulted in a more significant digging suppression against red imported fire ant workers at concentrations ranging between 19.5 and 0.6 µg/g than the solvent control whereas sand removal at 0.3 µg/g was similar with the solvent control. Black imported fire ants showed repellency at serial concentrations ranging between 19.5 and 0.15 µg/g whereas the hybrid imported fire ants showed repellency between 19.5 and 4.9 µg/g. In DEET treatments, red and black imported fire ants showed repellency at dosages of 125 to 62.5 µg/g, whereas the treatment failed at the dose of 15.6 µg/g in hybrid fire ants. (E/Z)-3-butylidenephthalide with LC₅₀ values of 11 and 16.4 µg/g was toxic against red and black imported fire ants, respectively, followed by hybrid imported fire ants (LC₅₀ = 104.7 µg/g). Fipronil with LC₅₀ values of 0.49, 0.33, and 0.53 µg/g against red, black, and hybrid fire ants, respectively, was more toxic than (E/Z)-3-butylidenephthalide. In residual bioassay, toxic activity lasted for 3 weeks at dosages of 250 and 500 μg/g against HIFA. The high repellency and toxicity of (E/Z)-3-butylidenephthalide against imported fire ants makes it a natural compound of interest for further evaluation under natural field conditions. Full article

The red imported fire ant Solenopsis invicta Buren (Hymenoptera: Formicidae) is native to South America; however, its introduction to other countries has caused serious biodiversity, agricultural, and public health problems. As toxic bait is an effective method to control fire ant populations, the aim of this study was to determine the most effective concentration of sulfoxaflor, flupyradifurone, and triflumezopyrim as ingredients for baits against S. invicta under laboratory and field conditions. Sulfoxaflor, flupyradifurone, and triflumezopyrim had no effect on the feeding behavior of the fire ants. However, they significantly reduced the climbing, walking, and arrest abilities of the fire ant workers after 10 days of treatment, and insecticides were horizontally transferred from workers to alates or larvae. Specifically, sulfoxaflor and triflumezopyrim at 0.05% concentration were the most effective in exterminating fire ants. Sulfoxaflor and triflumezopyrim are nonrepellent and effective insecticides against S. invicta. Full article

In order to express the energy flow, motion flow, and control flow in wireless rechargeable sensor networks accurately and intuitively, and to maximize the charging benefit of MVs (mobile vehicles), a type of MTS-HACO (Mobile Transition Sequence Hybrid Ant Colony Optimization) is proposed. Firstly, node places are grouped according to the firing time of node’s energy consumption transition to ensure that in each time slot, MV places only enable charging transitions for the node places with lower remaining lifetimes. Then, the FSOMCT (Firing Sequence Optimization of Mobile Charging Transition) problem is formulated under the constraints of MV places capacity, travelling arc weight, charging arc weight, and so on. The elite strategy and the Max–Min Ant Colony system are further introduced to improve the ant colony algorithm, while the improved FWA (fireworks algorithm) optimizes the path constructed by each ant. Finally, the optimal mobile charging transition firing sequence and charging times are obtained, ensuring that MVs have sufficient energy to return to the base station. Simulation results indicate that, compared with the periodic algorithm and the PE-FWA algorithm, the proposed method can improve charging benefit by approximately 48.7% and 26.3%, respectively. Full article

Native ants have long been considered for their potential to suppress the red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae), a highly invasive and destructive species. However, the knowledge in this field is limited to behavioral observations of a few related native ants. In this study, by setting up a series of ant combinations of three native ants, i.e., Monomorium chinense Santschi, the robust crazy ant Nylanderia bourbonica Forel, and Iridomyrmex anceps Roger, with S. invicta, we observed the aggression levels and mortality rates. Using baited vials, we also investigated the abundance of native ants in four types of habitats in Eastern China that are preferred by S. invicta (woodland, green belts on roadsides, grassland, and farmland), as well as their seasonal abundance when co-existing with S. invicta and their spatial distribution before and after control of S. invicta. We found that M. chinense and N. bourbonica show a degree of aggression towards S. invicta and can kill substantial proportions of S. invicta under laboratory conditions, but I. anceps does not. Both M. chinense and N. bourbonica can occur in each type of habitat investigated and are more abundant in green belts (particularly lawns with turf) and grasslands relative to other habitats. In grasslands with S. invicta, M. chinense maintained a low density before early July; however, its abundance increased thereafter and reached a peak in September. N. bourbonica also had a low density early in the season and increased steadily from April. Its abundance began to decrease substantially from November. In grasslands invaded by S. invicta, both M. chinense and N. bourbonica were restricted to sites close to the margins before S. invicta was controlled; however, they spread to a larger range within a few weeks after control of S. invicta. In conclusion, M. chinense and N. bourbonica have the potential to suppress S. invicta invasion in habitats that are abundant with these two native ants. Full article

The red imported fire ant (Solenopsis invicta Buren) is one of the 100 worst invasive alien species in the world. At present, the control of red imported fire ants is still mainly based on chemical control, and the most commonly used is indoxacarb bait. In this study, the contact and feeding toxicity of 16 kinds of nanomaterials to workers, larvae, and reproductive ants were evaluated after 24 h, 48 h, and 72 h. The results showed that the mortality of diatomite, Silica (raspberry-shaped), and multi-walled carbon nanotubes among workers reached 98.67%, 97.33%, and 68%, respectively, after contact treatment of 72 h. The mortality of both larval and reproductive ants was less than 20% after 72 h of treatment. All mortality rates in the fed treatment group were below 20% after 72 h. Subsequently, we evaluated the digging, corpse-removal, and foraging behaviors of workers after feeding with diatomite, Silica (raspberry-shaped), and multi-walled carbon nanotubes for 24 h, which yielded inhibitory effects on the behavior of red imported fire ants. The most effective was diatomite, which dramatically decreased the number of workers that dug, extended the time needed for worker ant corpse removal and foraging activities, decreased the number of workers that foraged, and decreased the weight of the food carried by the workers. In addition, we also evaluated the contact and feeding toxicity of these three nanomaterials in combination with indoxacarb on red imported fire ants. According to contact toxicity, after 12 h of contact treatment, the death rate among the red imported fire ants exposed to the three materials combined with indoxacarb reached more than 97%. After 72 h of exposure treatment, the mortality rate of larvae was more than 73% when the nanomaterial content was above 1% and 83% when the diatomite content was 0.5%, which was significantly higher than the 50% recorded in the indoxacarb control group. After 72 h of feeding treatment, the mortality of diatomite, Silica (raspberry-shaped), and multi-walled carbon nanotubes combined with indoxacarb reached 92%, 87%, and 98%, respectively. The death rates of the three kinds of composite ants reached 97%, 67%, and 87%, respectively. The three kinds of composite food had significant inhibitory effects on the behavior of workers, and the trend was largely consistent with the effect of nanomaterials alone. This study provides technical support for the application of nanomaterials in red imported fire ant control. Full article