Hydrocarbons in Formicidae: influence of chemical footprints on ant behavioral strategies

When an insect walks, it leaves chemical cues that derive from the arolium, a tarsal structure. These cues may contain important information about other species that occur in their community and can then mediate interactions of competition, predation, and information about resources with ants from their own colony. The compounds of these cues are released into the substrate in the form of chemical footprints. There are still few species studied, and little is known about the behavior of ants regarding these signals and how they use them in their interactions. Therefore, the aim of this study was to assess the behavioral strategy of different ant species when confronted with chemical footprints left by other ants, as well as identify their compounds and their relationship with the cuticular hydrocarbon profile. The experiments were performed using a Y-maze, where in one of the arms, there were chemical footprints of their own species or of other species, and the other Y arm was footprint-free. The chemical compounds of footprints and cuticle were analyzed by gas chromatography-mass spectrometry. The results show that foragers of all species detect and respond to the presence of chemical cues in the form of footprints left by other ants. Foragers of all species followed footprints of individuals of the same species both nestmates and non-nestmates; however, Neoponera villosa avoided the footprints of Cephalotes borgmeieri, and C. borgmeieri avoided the footprints of the other two species. The chemical compositions of the cuticle and footprints are related to each other and are specific to each species.

Description of the male of Erromyrma Bolton & Fisher, 2016 (Hymenoptera, Formicidae)

The male of the myrmicine genus Erromyrma is described for the first time on the basis of two specimens of Erromyrmalatinodis (Mayr, 1872) collected in northern Madagascar. We used COI barcoding to confirm the identification of the male specimens as conspecific with Erromyrmalatinodis. We provide an illustrated male-based key to the four Myrmicinae tribes (Attini, Crematogastrini, Solenopsidini, Stenammini) and to the Solenopsidini genera (Adelomyrmex, Erromyrma, Solenopsis, Syllophopsis and Monomorium) for the Malagasy region.

The Evolution of Tyramides in Male Fungus-Growing Ants (Formicidae: Myrmicinae: Attini: Attina)

Ants use a variety of semiochemicals for essential activities and have been a source for many novel natural products. While ant taxa produce a wide variety of chemicals, the chemistry and ecology of male ants have remained understudied. Tyramides are a class of compounds that have been found only in males of the Myrmicinae ant subfamily. Tyramides found in the fire ant Solenopsis invicta are transferred to gynes during mating where they are converted to tyramine, leading to rapid reproductive development. To further understand the evolution of tyramide production in male ants, we determined the tyramide composition in males of 15 fungus-growing ant species (Formicidae: Myrmicinae: Attini: Attina) and a Megalomyrmex species (Formicidae: Myrmicinae: Solenopsidini). Thirteen tyramides were identified, four for the first time in natural sources, and their percent composition was mapped to the fungus-growing ant phylogeny.

The complete mitochondrial genome of Aphaenogaster japonica (Forel, 1911) (Hymenoptera: Formicidae)

Aphaenogaster japonica (Forel, 1911) is an omnivorous ant that is widely distributed in eastern Asia. The mitochondrial genome of A. japonica reported here was 18,607 bp in length, consisting of 13 protein-coding genes, two ribosomal RNA genes, 22 transfer RNA genes, and a control region. The base composition was AT biased (the GC ratio is 18.9%). With A. japonica added, we obtain weak evidence that the sister group of the Stenammini group, including Aphaenogaster, is the Myrmicini group. Therefore, the Stenammini and Myrmicini groups may be not a robust monophyletic group, unlike the previous results based on the complete mitochondrial genome.

The Male of the Ant Genus Rhopalothrix (Hymenoptera: Formicidae: Myrmicinae)

The male caste is firstly described for the ant genus Rhopalothrix. The male was collected as attached to the gyne during copula. Due to the rarity of the genus, the gyne and male are tentatively associated with R. apertor Longino and Boudinot 2013. The apomorphic features of Rhopalothrix male are discussed, and a preliminary identification key based on males to the genera in the Basiceros-genus group (formerly tribe Basicerotini) is provided.

The complete mitochondrial genome of Pheidole nodus (Smith, 1874) (Hymenoptera: Formicidae)

Pheidole nodus (Smith, 1874) belongs to a famously hyperdiverse and ecologically dominant ant genus. The mitochondrial genome of P. nodus is 15,579 bp in length, and the overall base composition is 78.6% AT. It includes 13 protein-coding genes, 2 ribosomal RNA genes, 22 transfer RNAs, and a control region. Phylogenetic trees show that P. nodus is more closely related to Wasmannia than to Atta. These sequence data will play an important role in the investigation of the phylogenetic relationships and taxonomy of the group Attini.

The complete mitochondrial genome of Tetramorium tsushimae (Emery, 1925) (Hymenoptera: Formicidae)

Tetramorium tsushimae (Emery, 1925) is an omnivorous ant species native to East Asia and has been introduced to North America. The mitochondrial genome of T. tsushimae is 19,207 bp in length with an A + T content of 81.3% and includes 13 protein-coding genes, 2 ribosomal RNA genes, 22 transfer RNAs, and a control region. This sequence data would play an important role in the investigation of mitochondrial evolution of the subfamily Myrmicinae.

Identification of the Trail Pheromone of the Pavement Ant Tetramorium immigrans (Hymenoptera: Formicidae)

Four species of Tetramorium pavement ants are known to guide foraging activities of nestmates via trail pheromones secreted from the poison gland of worker ants, but the trail pheromone of T. immigrans is unknown. Our objectives were to (1) determine whether poison gland extract of T. immigrans workers induces trail-following behavior of nestmates, (2) identify the trail pheromone, and (3) test whether synthetic trail pheromone induces trail-following behavior of workers. In laboratory no-choice bioassays, ants followed poison-gland-extract trails farther than they followed whole-body-extract trails or solvent-control trails. Gas chromatographic-electroantennographic detection (GC-EAD) analyses of poison gland extract revealed a single candidate pheromone component (CPC) that elicited responses from worker ant antennae. The CPC mass spectrum indicated, and an authentic standard confirmed, that the CPC was methyl 2-methoxy-6-methylbenzoate (MMMB). In further laboratory no-choice bioassays, ants followed poison-gland-extract trails (tested at 1 ant equivalent) and synthetic MMMB trails (tested at 0.35 ant equivalents) equally far, indicating that MMMB is the single-component trail pheromone of T. immigrans. Moreover, in laboratory two-choice bioassays, ants followed MMMB trails ~ 21-times farther than solvent-control trails. In field settings, when T. immigrans colonies were offered a choice between two paper strips treated with a synthetic MMMB trail or a solvent-control trail, each leading to an apple bait, the MMMB trails efficiently recruited nestmates to baits.

Using an integrative taxonomic approach to delimit a sibling species, Mycetomoellerius mikromelanos sp. nov. (Formicidae: Attini: Attina)

The fungus-growing ant Mycetomoellerius (previously Trachymyrmex) zeteki (Weber 1940) has been the focus of a wide range of studies examining symbiotic partners, garden pathogens, mating frequencies, and genomics. This is in part due to the ease of collecting colonies from creek embankments and its high abundance in the Panama Canal region. The original description was based on samples collected on Barro Colorado Island (BCI), Panama. However, most subsequent studies have sampled populations on the mainland 15 km southeast of BCI. Herein we show that two sibling ant species live in sympatry on the mainland: Mycetomoellerius mikromelanos Cardenas, Schultz, & Adams and M. zeteki. This distinction was originally based on behavioral differences of workers in the field and on queen morphology (M. mikromelanos workers and queens are smaller and black while those of M. zeteki are larger and red). Authors frequently refer to either species as "M. cf. zeteki," indicating uncertainty about identity. We used an integrative taxonomic approach to resolve this, examining worker behavior, chemical profiles of worker volatiles, molecular markers, and morphology of all castes. For the latter, we used conventional taxonomic indicators from nine measurements, six extrapolated indices, and morphological characters. We document a new observation of a Diapriinae (Hymenoptera: Diapriidae) parasitoid wasp parasitizing M. zeteki. Finally, we discuss the importance of vouchering in dependable, accessible museum collections and provide a table of previously published papers to clarify the usage of the name T. zeteki. We found that most reports of M. zeteki or M. cf. zeteki-including a genome-actually refer to the new species M. mikromelanos.

A new species group of Strumigenys (Hymenoptera, Formicidae) from Ecuador, with a description of its mandible morphology

Strumigenys is one of the most diverse ant genera in the world and arguably the most morphologically diverse, exhibiting an exceptional range of mandible shape and function. A new species, Strumigenysayerstheysp. nov., discovered in the Chocó region of Ecuador is described. With two morphological characters, this species is shown to be a morphologically unique outlier among Strumigenys globally, having predominately smooth and shining cuticle surface sculpturing and long trap-jaw mandibles. Using µCT scans, we produced 3D images of the worker ant and static images to examine and compare mandible articular morphologies with most morphologically similar members of the mandibularis species group. Cuticular, pilosity, and articular mandible morphological differences supports placing the new species in its own new species group.

Influence of host phylogeny, geographical location and seed harvesting diet on the bacterial community of globally distributed Pheidole ants

The presence of symbiotic relationships between organisms is a common phenomenon found across the tree of life. In particular, the association of bacterial symbionts with ants is an active area of study. This close relationship between ants and microbes can significantly impact host biology and is also considered one of the driving forces in ant evolution and diversification. Diet flexibility of ants may explain the evolutionary success of the group, which may be achieved by the presence of endosymbionts that aid in nutrition acquisition from a variety of food sources. With more than 1,140 species, ants from the genus Pheidole have a worldwide distribution and an important role in harvesting seeds; this behavior is believed to be a possible key innovation leading to the diversification of this group. This is the first study to investigate the bacterial community associated with Pheidole using next generation sequencing (NGS) to explore the influences of host phylogeny, geographic location and food preference in shaping the microbial community. In addition, we explore if there are any microbiota signatures related to granivory. We identified Proteobacteria and Firmicutes as the major phyla associated with these ants. The core microbiome in Pheidole (those found in >50% of all samples) was composed of 14 ASVs and the most prevalent are family Burkholderiaceae and the genera Acinetobacter, Streptococcus, Staphylococcus, Cloacibacterium and Ralstonia. We found that geographical location and food resource may influence the bacterial community of Pheidole ants. These results demonstrate that Pheidole has a relatively stable microbiota across species, which suggests the bacterial community may serve a generalized function in this group.

The complete mitochondrial genome of Aphaenogaster famelica (Smith, 1874) (Hymenoptera: Formicidae)

Aphaenogaster famelica (Smith, 1874) is a slender ant found in Korea. We have completed the mitochondrial genome of A. famelica of which length is 19,464 bp, the third longest ant mitogenome so far. It was AT-biased (GC ratio is 18.0%) and includes 13 protein-coding genes, two ribosomal RNA genes, 22 transfer RNA genes, and a control region. The extra bases of A. famelica are placed in intergenic regions each between trnV-trnM and trnI-trnQ. Gene order of A. famelica is identical to other Myrmicinae ants. Phylogenetic trees show that tribe Stenammini and tribe Myrmicini are closely related.

Identification and Functional Characterization of a Novel Insecticidal Decapeptide from the Myrmicine Ant Manica rubida

Ant venoms contain many small, linear peptides, an untapped source of bioactive peptide toxins. The control of agricultural insect pests currently depends primarily on chemical insecticides, but their intensive use damages the environment and human health, and encourages the emergence of resistant pest populations. This has promoted interest in animal venoms as a source of alternative, environmentally-friendly bio-insecticides. We tested the crude venom of the predatory ant, Manica rubida, and observed severe fitness costs in the parthenogenetic pea aphid (Acyrthosiphon pisum), a common agricultural pest. Therefore, we explored the M. rubida venom peptidome and identified a novel decapeptide U-MYRTX-MANr1 (NH₂-IDPKVLESLV-CONH₂) using a combination of Edman degradation and de novo peptide sequencing. Although this myrmicitoxin was inactive against bacteria and fungi, it reduced aphid survival and reproduction. Furthermore, both crude venom and U-MYRTX-MANr1 reversibly paralyzed injected aphids and induced a loss of body fluids. Components of M. rubida venom may act on various biological targets including ion channels and hemolymph coagulation proteins, as previously shown for other ant venom toxins. The remarkable insecticidal activity of M. rubida venom suggests it may be a promising source of additional bio-insecticide leads.

Proteomic Analysis of the Venom from the Ruby Ant Myrmica rubra and the Isolation of a Novel Insecticidal Decapeptide

Ants are a biodiverse group of insects that have evolved toxic venom containing many undiscovered bioactive molecules. In this study, we found that the venom of the ruby ant Myrmica rubra is a rich source of peptides. LC-MS analysis revealed the presence of 142 different peptides varying in molecular weight, sequence length, and hydrophobicity. One of the most abundant peaks was selected for further biochemical and functional characterization. Combined Edman degradation and de novo peptide sequencing revealed the presence of a novel decapeptide (myrmicitoxin) with the amino acid sequence NH₂-IDPKLLESLA-CONH₂. The decapeptide was named U-MYRTX-MRArub1 and verified against a synthetic standard. The amidated peptide was tested in a synthetic form to determine the antimicrobial activity towards the bacterial pathogens and insecticidal potential against pea aphids (Acyrthosiphon pisum). This peptide did not show antimicrobial activity but it significantly reduced the survival of aphids. It also increased the sensitivity of the aphids to two commonly used chemical insecticides (imidacloprid and methomyl). Since ant venom research is still in its infancy, the findings of this first study on venom peptides derived from M. rubra highlight these insects as an important and rich source for discovery of novel lead structures with potential application in pest control.

Ants of the Monomorium monomorium species-group (Hymenoptera: Formicidae) in the Arabian Peninsula with description of a new species from southwestern Saudi Arabia

We revise the taxonomy of the myrmicine ants of the Monomorium monomorium species-group for the Arabian Peninsula. Six species are recognized: Monomorium aeyade Collingwood & Agosti, 1996, M. clavicorne André, 1881, M. exiguum Forel, 1894, M. holothir Bolton, 1987, M. mohammedi sp. n., and M. sarawatense Sharaf & Aldawood, 2013. On the basis of the worker caste, we describe Monomorium mohammedi sp. n. from the southwestern region of the Kingdom of Saudi Arabia (KSA). We designate a neotype for Monomorium aeyade Collingwood & Agosti and redescribe and illustrate the worker caste. Furthermore, we provide a worker-based species identification key, distribution maps for the treated species, and ecological and biological notes, if available. Monomorium holothir is recorded for the first time from the KSA. Also, we propose M. clavicorne var. punicaSantschi, 1915a as a junior synonym of M. clavicorne, as well as M. dryhimi Aldawood & Sharaf, 2011 and M. montanum Collingwood & Agosti, 1996 to be treated as junior synonyms of Monomorium exiguum.

A new species of Trachymyrmex (Hymenoptera, Formicidae) fungus-growing ant from the Sierra Madre Oriental of northeastern Mexico

Here we describe a new species of Trachymyrmex, T. pakawasp. n., from the Gran Sierra Plegada range of the Sierra Madre Oriental, in the states of Coahuila and Nuevo Leon, northeastern Mexico. Trachymyrmex pakawa is a large-sized species compared to other North American Trachymyrmex. Its geographic distribution includes the piedmont of the Gran Sierra Plegada at La Estanzuela, Monterrey, as well as peripheral mountains segregated from the Sierra Madre Oriental (Cerro de las Mitras, Sierra de Zapalinamé, Cañon de San Lorenzo, Cerro de las Letras). The preferred habitats of T. pakawa include oak-pine forest at La Estanzuela, xeric oak forest at Zapalinamé and mesic Chihuahuan desert scrub with sotol (Dasylirion) at other sites. All localities are on slopes, on very rocky, shallow lithosols overlaying large boulders. This species nests under and between large boulders and rocks. It has not been observed on alluvial or better developed, deeper soils, and it is absent from sites with human activity (urban, disturbed, and landscaped areas). It is closely related to and morphologically similar to Trachymyrmex smithi. The known distribution ranges of T. pakawa and T. smithi almost overlap in Saltillo, Coahuila state. The main character that distinguishes the new species from T. smithi is longer antennal scapes in T. pakawa; also, different nesting habits (rocky slopes vs. alluvial sites or deep sand in T. smithi), and geographic distribution. Phylogenetic analysis of DNA sequences from the mitochondrial marker cytochrome c oxidase subunit I (COI) and the first intron of the F1 copy of the nuclear protein-coding gene Elongation Factor 1- α (EF1-α-F1) confirm a sister-species relationship between T. pakawa and T. smithi. Bayesian coalescent analyses indicate a divergence time of about 8.00 million years before present (95% confidence interval: 4.8-11.5 mya) between T. pakawa and T. smithi. The divergence of the lineages of T. pakawa and T. smithi could have been driven by the Pliocene-Holocene desertification of southwestern North America. This process resulted in isolated mesic refugia and forests in the Madrean ranges and piedmonts of northeastern Mexico (the current habitat of T. pakawa) while T. smithi adapted to the deeper, often sandy soils on the drier desert plains of Coahuila and Chihuahua states in Mexico, and New Mexico and Texas in the USA. Within the Nearctic species of the Trachymyrmex septentrionalis species group, T. pakawa is the species that is closest (by geographical distribution) to Neotropical species of Trachymyrmex like T. saussurei.

The ant genus Carebara Westwood in the Arabian Peninsula (Hymenoptera, Formicidae)

The ant genus Carebara of the Arabian Peninsula is revised. Carebara abuhurayri Sharaf & Aldawood, 2011 is synonymized under Carebara arabica Collingwood & van Harten, 2001. Carebara arabica is redescribed and a Neotype is fixed based on a specimen collected from southwestern Kingdom of Saudi Arabia. A new species, C. fayrouzae sp. n. is described from Saudi Arabia based on queens, major and minor workers. Keys to major and minor workers of the two Arabian Carebara species are given.

Pristomyrmex tsujii sp. n. and P. mandibularis Mann (Hymenoptera, Formicidae) from Fiji

Pristomyrmex tsujiisp. n., an endemic species of the Fiji islands, is described from the worker, ergatoid queen, alate queen and male castes. The alate queen and male castes of Pristomyrmex mandibularis Mann are also described for the first time. The ergatoid queens for both species appear to be morphologically intermediate between the worker and alate queen castes. Pristomyrmex tsujii is readily distinguished from Pristomyrmex mandibularis by the lack of well-developed propodeal spines. Although both species occur across the Fijian archipelago, they are rarely encountered and workers are most often collected from sifted litter. The descriptions are illustrated with specimen photographs, line drawings and a distribution map.

Taxonomic studies on genus Tetramorium Mayr (Hymenoptera, Formicidae) with report of two new species and three new records including a tramp species from India with a revised key

Two new species of Tetramorium Mayr, namely Tetramorium shivalikensesp. n. and Tetramorium triangulatumsp. n. are described. Tetramorium triangulatumsp. n. belongs to the inglebyi-species group and is described based on worker, queen and male caste, while Tetramorium shivalikensesp. n. belongs to the ciliatum-species group and is described based on worker caste only. Three species viz., Tetramorium caldarium (Roger), Tetramorium tonganum Mayr and Tetramorium urbanii Bolton represent first records from India. The male caste is described for the first time in the case of Tetramorium tonganum. Among these, Tetramorium caldarium is a tramp species which extends its limit to India as well. A revised key to the Indian ants of this genus is also provided herewith.

Monomorium dryhimi sp. n., a new ant species (Hymenoptera, Formicidae) of the M. monomorium group from Saudi Arabia, with a key to the Arabian Monomorium monomorium-group

A new ant species, Monomorium dryhimi, is described based on workers from a single colony collected in Al Bahah, Asir Province, Saudi Arabia. This is the fourth species of the Monomorium monomorium-group collected from Arabian Peninsula, and appears to be closely related to Monomorium holothir Bolton, 1987, from Kenya. It can be distinguished by the following characters: head in profile with a weakly convex dorsal surface and a clearly convex ventral surface; eyes of moderate size with maximum diameter EL 0.19–0.25 × HW and with 6 ommatidia in the longest row; body colour yellow to light brownish yellow. In some individuals, head and gaster slightly but conspicuously darker than rest of body. Second halves of first and second gastral tergites with two characteristic brownish transverse bands. An identification key to the workers of the Arabian species of the Monomorium monomorium-group is presented. Scanning electron micrographs are given to illustrate the new species.

First record of the myrmicine ant genus Carebara Westwood, 1840 (Hymenoptera, Formicidae) from Saudi Arabia with description of a new species, C. abuhurayri sp. n

The myrmicine ant genus Carebara is recorded for the first time in Saudi Arabia from the Arabian Peninsula as a whole. A new species Carebara abuhurayrisp. n. is described based on workers collected from Al Bahah region. One of the smallest ant species known to occur in Arabia, Carebara abuhurayri is found in an area inhabited by many ant species including Tetramorium sericeiventre Emery, 1877, Pheidole minuscula Bernard, 1952, Pheidole sp., Monomorium destructor (Jerdon, 1851), Monomorium exiguum (Forel, 1894) and Monomorium sp. and Crematogaster sp.