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

﻿Abstract 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.


Introduction
Within the Malagasy region, Myrmicinae is one of the largest and most diverse subfamilies of Formicidae (Hymenoptera), with 30 genera in four tribes (Fisher and Peeters 2019;Fisher 2022). The genus Erromyrma Bolton & Fisher, 2016 (Solenopsidini), is represented by one species in the Malagasy region, Erromyrma latinodis (Mayr, 1872).
The species has been introduced in many countries, including the Malagasy region, and is thought to have originated in India (Sharaf et al. 2018). The global distribution also includes Indomalaya, the Southeastern Palearctic and Oceania bioregions. Erromyrma latinodis was originally placed in Monomorium but was shown to be a distinct lineage within the Solenopsidini based on molecular phylogenetic evidence (Ward et al. 2015) and placed in the newly described genus Erromyrma. Here we present the first description of the previously unknown male of Erromyrma based on E. latinodis, collected in northern Madagascar. We provide a male-based key to the Myrmicinae tribes and to genera for the tribe Solenopsidini of the Malagasy region.

Material and methods
This study is based on two male ant specimens (unique specimen identifiers: CASENT0788835 and CASENT0801166) collected in northern Madagascar in the town of Antsohihy (-14.89385, 47.98261) in the Region of Sofia, at c. 11 m above sea level on April 23, 2017, by Brian L. Fisher and the Madagascar Biodiversity Center team (Team Vitsika). Two males along with workers and queens were collected by hand under the bark of a mango tree along a dirt road 1 km outside of the town of Antsohihy (collection code identifiers: BLF40204, BLF40205). The mango tree was 1.5 m in diameter and approximately 5 m tall. The ants were found under bark flakes before the first branch at about 1 m in height.
Terminology for general morphology follows Bolton (1994) and Boudinot (2013Boudinot ( , 2015. The terminology of the wing venation follows Yoshimura and Fisher (2007). When referring to the presence or absence of veins in the descriptions, a vein is considered present regardless of whether it is tubular, nebulous, or spectral (Mason 1986).

Imaging
Digital color montage images were created using a JVC KY-F75 digital camera and Syncroscopy Auto-Montage software (ver. 5.0), or a Leica DFC 425 camera in combination with the Leica Application Suite software (ver. 3.8). These images are available online through AntWeb.org (2022) and are accessible using the unique specimen identifier code.

Mapping
The distribution map was generated by importing specimen distribution records into the Diva-GIS program (Hijmans et al. 2011).

Morphological study
Morphological observations and measurements were carried out under Leica stereoscopic microscopes (MZ9.5). All measurements (see Fig. 1) and indices are expressed in millimeters.
The following characters were recorded:

EL:
Maximum eye length measured in full-face view along its maximum vertical diameter.

F1:
Maximum length of the pedicel (1 st funicular segment, 2 nd antennal segment) measured in a straight line. HL: Maximum head length in full-face view, measured in a straight line, from the anterior clypeal margin to the midpoint of a straight line drawn across the occipital margin.

HW1:
Head width at the level of the posterior margin of compound eyes, measured in full-face view. HW2: Maximum head width including the compound eyes, measured in full-face view. IOD: Inner ocellar distance. Minimum distance between the inner edges of the two lateral ocelli, measured in full-face view. LOD: Lateral ocellar distance. Minimum distance between the inner edge of the median and lateral ocelli, measured in full-face view. OOD: Ocular-ocellar distance. Minimum distance from the outer edge of a lateral ocellus to the compound eyes, measured in full-face view.

PL:
Petiole length, measured in profile view from the anterior margin of the peduncle to posterior most point of the petiolar tergite. PW: Petiolar width. Maximum petiole width, measured in dorsal view. PPW: Postpetiolar width. Maximum postpetiole width, measured in dorsal view.

SL:
Scape length. Maximum length of the antennal scape measured in a straight line, excluding the basal constriction and condylar bulb.

DNA sampling
After searching for the males in colonies across Madagascar for six years, we wanted to confirm that these males did represent the first males of E. latinodis even though they were collected along with queens and workers. We sequenced 658 base pairs (bp) of mitochondrial cytochrome oxidase I (COI) gene from one of the males to evaluate similarity with CO1 sequenced from 33 workers of E. latinodis across the region. The distribution of the specimens sequenced is shown in Fig. 10. DNA extraction and COI sequencing were performed at University of Guelph (Ontario, Canada), following the protocol described in Fisher and Smith (2008

Description. Erromyrma latinodis males:
Structure. In full-face view, the head including compound eyes slightly wider than long. Posterior head margin relatively rounded; head with three large, rounded ocelli of the same size, situated on the frontal face of the head, lateral ocelli directed 45° toward lateral sides. Compound eye large, strongly bulging. Anterior margin of clypeus convex. Mandible well developed and elongate triangular; masticatory margin with four teeth, the basal and masticatory margins are distinct.
Antennae 13-segmented short and filiform, pedicel subglobular. The mesoscutum is strongly convex and bulging, in the dorsal view much broader than the head at the level of the forewing insertion. In dorsal view, pronotum short in the median portion; notauli absent on the mesoscutum; mesoscutellum broader than long and smaller than mesoscutum. Metapleural gland bulla present with metapleural lobe closed. In profile, propodeal angle rounded, without spines or teeth. Hind femora longer than tibia.
In lateral view, petiole distinctly pedunculated; subpetiolar process absent ( Fig. 2A). In dorsal view, abdominal segment III (postpetiole) elongated anteriorly; abdominal segment IV not shoulder and broader than the remaining tergites. Sculpture. Clypeus, dorsum, lateral face, and venter of head weakly smooth and shiny. Pro-and mesothorax extensively smooth or very superficially sculptured and shiny, with posterolateral area of mesoscutum and posterior zone of mesopleuron unsculptured with shiny area. Metanotum and metapleuron unsculptured and matte. Apical area of anterior slope of petiole, coxae, femora, and tibiae of all legs smooth to superficially sculptured and shiny; tarsi entirely microsculptured. Gaster (abdominal segments IV to the apex) entirely smooth to superficially sculptured and shiny.
Color. Body and mandible largely brownish yellow except the ocellar region and the abdominal segments IV to the apex, brown.

1
In profile, occipital carina strongly developed (Fig. 4A); mesoscutellum strongly elevated above metanotum; in dorsal view, scutellum smooth and convex (Fig. 4C)  In profile, posterodorsal margin of head almost straight from the base of the lateral ocelli to the midpoint of the occipital carina. (Fig. 5A)  In profile, posterodorsal margin of head gradually rounded from the base of the lateral ocelli to the midpoint of the occipital margin. (Fig. 5B)

4
Mandible strongly developed; masticatory margin with 7 large teeth which increase in size from apex to base; between each tooth is a minute denticle (Fig. 7A)    Male-based key to genera of the tribe Solenopsidini in the Malagasy region Forewing with five closed cells, 1m-cu cross-vein present (Fig. 10A). In profile, petiolar peduncle longer than postpetiolar length (Fig. 10C) (Fig. 10B). In profile, petiolar peduncle absent or shorter than postpetiolar length (Fig. 10D) .........4   With the head in full-face view, antennal scape short, barely reaching the posterior ocular margin; mandible long, curved, masticatory margin with 3 to 4 teeth (Fig. 11A)

Discussion
In the Malagasy region, Erromyrma latinodis was collected from Comoros, Madagascar and Mayotte (see Fig. 12). The species inhabits montane rainforest, mangrove, Uapaca woodland, dry forest, and anthropogenic habitats from elevations of 2 to 1726 m. Workers were collected from a range of microhabitats and methods including foraging on low vegetation, on the ground, in ground nests, sifted litter, under stones, rotten wood or from dead twigs above ground. The males were collected along with workers and queens under the bark on the main trunk of a mango tree along a village road. The males for this species were only collected after six expeditions. They are not collected by traditional means for example: malaise traps sampling or UV light samples from the region. Initial expeditions to known localities in northern Madagascar did not find the males. Colonies were kept alive for over a year without the production of males. Two males were finally found at one of the known collection sites.
The C01 data confirms the identification of the males and also shows a pattern of 0% sequence divergence between the samples from Madagascar, Comoros, and Mayotte. The lack of sequence divergence across island systems supports the hypothesis that this species is introduced in the region. Low sequence diversity could also be explained by other factors such as reproductive systems. The difficulty of finding males could be linked to a reproductive system that would reduce sequence divergence.