# Systematics and early evolution of ants (Hymenoptera: Formicidae): the first male and worker-queen association for †Gerontoformica

Yuhui Zhuang, Vincent Perrichot, Jiahao Li, De Zhuo, Yu Liu, Bo Wang, Qingqing Zhang, Brendon E Boudinot

► To cite this version:

Yuhui Zhuang, Vincent Perrichot, Jiahao Li, De Zhuo, Yu Liu, et al.. Systematics and early evolution of ants (Hymenoptera: Formicidae): the first male and worker-queen association for †Gerontoformica. Myrmecological News, 2025, 35, pp.89-98. 10.25849/myrmecol.news_035:089. insu-05024816

HAL Id: insu-05024816

https://insu.hal.science/insu-05024816v1

Submitted on 8 Apr 2025

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
<figure><img src="image_2.png" /></figure>

# Systematics and early evolution of ants (Hymenoptera: Formicidae): the first male and worker-queen association for †*Gerontoformica*

Yuhui ZHUANG, Vincent PERRICHOT, Jiahao LI, De ZHUO, Yu LIU, Bo WANG, Qingqing ZHANG & Brendon E. BOUDINOT

## Abstract

The ant colony is a life unit for ants consisting of different female castes and males. Workers are mainly responsible for feeding and defence, while the queen and males are mainly responsible for colony continuity. The queen is also rarely active away from the nest, let alone preserved as a fossil with other workers. Male ants develop from unfertilised ant eggs, and the vast morphological differences make identification of males so difficult and often neglected in fossils that they are known as the 'forgotten caste'. In this study, we introduce †*Gerontoformica priapos sp.n.* based on a male specimen and report for the first time the discovery of an ant colony specimen that includes both morphologically differentiated queen and worker castes of stem ants in a single piece of mid-Cretaceous Kachin amber. The type specimen of †*Gerontoformica priapos sp.n.* features well-preserved genitalia and wing venation, filling a critical gap in our comparative studies of sexual morphological differentiation in stem-group ants. Additionally, the discovery of this ant colony provides new insights into the morphological differentiation among different castes of †*Gerontoformica* females. To facilitate future research, we also provide detailed morphological diagrams for the various castes and sexes of †*Gerontoformica*.

**Key words:** Kachin amber, male ant, castes differentiation, sexual dimorphism, Cretaceous.

Received 9 September 2024; revision received 13 January 2025; accepted 14 January 2025

Subject Editor: Herbert Zettel

Yuhui Zhuang, Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, South Waihuan Road, Chenggong District, Kunming 650500, China; State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, 218000, China; Géosciences Rennes (UMR 6118), University Rennes, CNRS, Rennes 35000, France.

Vincent Perrichot, Géosciences Rennes (UMR 6118), University Rennes, CNRS, Rennes 35000, France.

Jiahao Li, State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, 218000, China; University of Chinese Academy of Sciences, Beijing 100049, China.

De Zhuo, Beijing Xiachong Amber Museum, 9 Shuanghe Middle Road, Beijing 100023, China.

Yu Liu & Qingqing Zhang (contact authors), Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, South Waihuan Road, Chenggong District, Kunming 650500, China.

E-mail: yu.liu@ynu.edu.cn; qqzhang@ynu.edu.cn

Bo Wang, State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, 218000, China.

Brendon E. Boudinot, Senckenberg Gesellschaft für Naturforschung, Senckenberganlage, 25, 6035, Frankfurt am Main, Germany.

## Introduction

Today, ants are the dominant surface-dwelling social insects, being found in all terrestrial ecosystems except Antarctica (HÖLLDOBLER & WILSON 1990, LACH & al. 2010). The origin of winged-wingless polyphenism in female Formicidae is a key morphological element of the

colonial lifestyle of ants (e.g., WHEELER 1910, WILSON 1953, HÖLLDOBLER & WILSON 1990) and is evidenced in the fossil record of stem group lineages by pieces containing either winged or wingless individuals (e.g., PERRICHOT & al. 2008, BARDEN & GRIMALDI 2013, CAO & al. 2020,
BOUDINOT & al. 2022a). Females with wings retain well-developed reproductive systems and serve as the “queens”, while those without form the mass of “workers” that undertake all essential tasks for colony growth and protection, including foraging, defense, and caring for brood and nestmates. Dealate queens usually remain within the nest and rarely engage in external activities (e.g., HÖLLDOBLER & WILSON 1990, PEETERS & ITO 2001, KELLER & al. 2014). Consequently, there are very few examples of queens directly fossilized alongside worker ants, and most queens in the fossil record are wing-bearing or alate (e.g., DLUSSKY 1999, LAPOLLA 2005, CAO & al. 2020, PERRICHOT & al. 2020, GUO & al. 2021). While the phenotypic plasticity of female ants has benefited the ants through the course of their evolutionary history, this has also starkly hindered our understanding of ants as colonial organisms in the fossil record. In particular, specimens that are not preserved together pose challenges for comparative morphological studies and species matching due to the pronounced morphological differences between queen and worker ants.

The phenotypic diversity of Formicidae is further expanded when accounting for the understudied phenomenon of sexual dimorphism. With the few exceptions of the feminized males of *Cataulacus*, the “pupoidal” males of inquilines (WILSON 1984) and some genera with occasional ergatoid males (*Hypoponera*, see YAMAUCHI & al. 1996; *Cardiocondyla*, see KINOMURA & YAMAUCHI 1987; *Technomyrmex*, see OGATA & al. 1996; *Platythyrea*, see BOUDINOT & al. 2016), male ants do not closely resemble females (BOUDINOT & al. 2021). This fact has greatly hindered the study of males as making male-female associations – hence the ability to place a species name on males – has been a historical challenge. The study of males has been further hindered because of a lack of interest, given that they do not participate in any social activities or work within the colony, with only extremely limited exception (e.g., HÖLLDOBLER 1966, BOUDINOT & al. 2016). The asocial behavior of males is reflected in their often vestigial or underdeveloped mandibles and metapleural (“antisepsis”) glands (e.g., BOUDINOT 2015, ULMER & al. 2023). The singular role of male ants in the context of the colonial lifestyle is reproduction, which may take place inside the nest among siblings, in great masses in species with nuptial flights or inconspicuously in species reliant on chemical signaling from virgin queens (e.g., PEETERS & MOLET 2010, METZLER & al. 2016, HELMS 2018). In those species that mate outside of the nest, males are not allowed to return to their nest of origin and inevitably face death (BOOMSMA & al. 2005, BOUDINOT & al. 2021), although some males have relatively long lifespans (SHIK & al. 2012). Notably, most males of social Hymenoptera are sperm-limited, as their testes degenerate before or shortly after adult emergence (HÖLLDOBLER & BARTZ 1985).

Despite being mere “sperm missiles” in the economic context of the colony, there are evident patterns of selection on males across multiple spectra including, for example, time-of-day for flight (e.g., MOSER & al. 2004) and competition for females who strictly mate singly (e.g.,

KIKUTA & TSUJI 1999, ALLARD & al. 2002) or multiply (e.g., BAER & BOOMSMA 2006). These patterns, in combination with developmental decoupling with the female castes, has resulted in quasi- to completely independent morphological character systems of males. In other words, contrary to general expectation, male ants are indeed identifiable to species level (e.g., RADCHENKO & ELMES 2010, YOSHIMURA & FISHER 2012, MACGOWN & al. 2014), and they provide both phylogenetic and evolutionary signal for the interogation of the evolutionary history of ants (BARDEN & al. 2017, BOUDINOT & al. 2021). However, male-female dimorphism has also resulted in the major limitation for understanding this “forgotten caste”: the accumulation of female-associated material through nest collections or sequencing. This issue is particularly pronounced for fosssils as males are very rarely preserved alongside females.

The fossil record of ants is rich in both described and undescribed species (LAPOLLA & al. 2013, BARDEN 2017) and documents the early radiation, turnover, and recovery of the Formicidae across the Cretaceous–Paleogene boundary (BOUDINOT 2024, JOUAULT & al. 2024, SOSIAK & al. 2024). Of particular importance are the fossils of the Cretaceous, which document both living groups of ants as well as extinct ant-wasp intermediate lineages (i.e., stem groups). Currently, the stem groups are classified in four subfamilies, the “ur-ants” (†Sphecomyrminae; BARDEN & GRIMALDI 2016, BOUDINOT & al. 2022a), the “hell ants” (†Haidomyrmecinae; PERRICHOT & al. 2016, BARDEN & al. 2020), the “iron maiden ants” (†Zigrasimeciinae; CAO & al. 2020, ZHUANG & al. 2022, 2024), and the likely sister group to the living ants, †Brownimeciinae (BARDEN & al. 2016, BOUDINOT & al. 2020, SOSIAK & al. 2024). The vast majority of the fossils attributed to these groups are female based, while males have been mostly attributed to the form taxon †*Baikuris*, the monophyly and association of which is uncertain.

Here, we report both the first syninclusion of winged and wingless conspecific female ants and the first male that is reasonably associated with females of one of the four stem group subfamilies. Both of these Kachin amber fossils represent the genus †*Gerontoformica* – a key group that has yielded substantial insights into the societal structure, behaviour, and anatomy of the stem lineages (BARDEN & GRIMALDI 2016, BOUDINOT & al. 2022a, RICHTER & al. 2022). Based on our morphological study, we provide detailed pattern drawings of †*Gerontoformica* male, queen, and worker, aiming to facilitating future comparative morphological studies of fossil ants. These fossils further our understanding of stem groups by providing the complete picture to date of an early ant colony.

## Material and methods

### Material

The studied fossils were found preserved in clear yellow pieces of Kachin amber (Figs. 1, 3). The materials were originally collected from an amber mine located near Noije Bum Village (26° 21' 33.41" N, 96° 43' 11.88" E),
Danai Town, northern Myanmar. An early Late Cretaceous
age (Early Cenomanian, 98.79 ± 0.62 average ± standard
error million years ago) for this amber was suggested by
radiometric and paleontological data (SHI & al. 2012, YU
& al. 2019).

The specimen YKLP-AMB-012 is housed at Yun-
nan University, Kunming, China, and the specimen
LYU-BM2005 is deposited in the Institute of Geology
and Paleontology at Linyi University, Linyi, China. All
specimens are permanently deposited in well-established,
public museums, in full compliance with the International
Palaeoentomological Society Statement (SZWEDO & al.
2020).

**Optical photomicrography**

Observations were performed using a Zeiss
(Oberkocher, Germany) Stemi 508 microscope. The pho-
tographs were taken with a Zeiss Stereo Discovery V16
microscope system in the Nanjing Institute of Geology
and Palaeontology, Chinese Academy of Sciences, and
measurements were taken using Zen software V2.3 pro.
Photomicrographic composites of 10 - 150 individual focal
planes were digitally stacked using the software Helicon-
Focus 6.7.1 for a better illustration of 3D structures. Pho-
tographs were adjusted using Adobe Lightroom Classic,
and line drawings were prepared using Illustrator 2020
(Adobe Systems Incorporated, San José, CA).

**Measurements and Indices**

The measurements (all in mm) and indices follow the
methodologies outlined by PERRICHOT & al. (2022) and
BOUDINOT & al. (2022b). Male-specific measurements are
indicated by an asterisk (*).

Measurements

**BL** (Body length): The total body length from the anterior margin of the head, excluding mandibles, to the apex of the abdomen, measured in lateral view.

**HL** (Head length): The length of the head capsule exclud-
ing the mandibles, measured in full-face view from a
line spanning the anteriormost points of the clypeal
lobes to a line spanning the posterior corners of the
head capsule.

**HW** (Head width): The maximum width of the head im-
mediately behind the eyes, measured in full-face view.

**HWE*** (Head width, eyes): The maximum width of the head, including the compound eyes.

**SL** (Scape length): The maximum straight-line length of the scape, excluding the basal constriction or neck just distal to the condylar bulb.

**EL** (Eye length): In profile, the maximum measurable length of the compound eye.

**WL** (Weber's length): The diagonal length of the mesosoma in profile, from the point where the pronotum meets the cervix to the posterior basal angle of the metapleuron.

**MscL*** (Mesoscutum length): The maximum length of the
mesoscutum, measured in dorsal view.

**MscW*** (Mesoscutum width): The maximum width of the
mesoscutum, measured in dorsal view.

**FWL*** (Forewing length): The maximum length of the forewing from the apices of the axillary sclerites to the wing apex.

**HWL*** (Hindwing length): The maximum length of the hindwing from the apices of the axillary sclerites to the wing apex.

**PH** (Petiole height): The maximum height of the petiole (abdominal segment 2), measured in lateral view.

**PL** (Petiole length): The maximum length of the petiole (abdominal segment 2), measured in lateral view.

**GL** (Gaster length): The maximum length of the gaster (abdominal segments 3 to 7), measured in lateral view.

**GW** (Gaster width): The maximum width of the gaster, measured in dorsal view.

Indices

**CI** (Cephalic index): Calculated as (HW / HL) × 100.

**HWI*** (Head width index): Calculated as (HW / HWE) × 100.

**SI** (Scape index): Calculated as (SL / HW) × 100.

**OI** (Ocular index): Calculated as (EL / HL) × 100.

**EPI** (Eye Position Index): In full-face view, the distance from a horizontal line that spans the anterior clypeal margin to one that spans the anterior margins of the eyes, divided by the distance from a horizontal line that spans the posterior margins of the eyes to one that spans the posterior corners of the head, × 100.

**MI*** (Mesoscutum Index): (MW / ML) × 100.

**PI** (Petiolar Index): (PL / PH) × 100.

**Results**

Systematic palaeontology

Family **Formicidae** LATREILLE, 1802

Subfamily †**Sphecomyrminae** WILSON & BROWN, 1967,
in WILSON & al. (1967)

Genus †**Gerontoformica** NEL & PERRAULT, 2004, in NEL & al. (2004)

Type species †*Gerontoformica creticica* NEL & PERRAULT, 2004, in NEL & al. (2004)

†*Gerontoformica priapos* ZHUANG, BOUDINOT & PER-
RICHOT sp.n.
(Figs. 1 - 2)

**Etymology:** Priapos was an ancient Greek fertility god, here used to indicate the male genitalia and to emphasize the importance of males for the reproduction of colonies.

**Material:** Holotype YKLP-AMB-012, male.

**Type locality and stratigraphy:** Hukawng Valley, Kachin Province, northern Myanmar. Upper Cretaceous, lower Cenomanian (ca. 98.79 ± 0.62 Ma; SHI & al. 2012). Housed at Yunnan University, Kunming, China.

**Diagnosis:** Mandible long, with two teeth; clypeus with short, tapered chaetae along the anterior margin (note: chaetae are a distinct class of sensilla trichodea, that are thicker than setae); frontal carina indistinct;
<figure><img src="image_3.png" /><figcaption>**Fig. 1:** †*Gerontoformica priapos* sp.n., holotype male, YKLP-AMB-012. General habitus in laterodorsal (A) and lateroventral (B) views. (C) Detail of head in frontal view; red arrows indicate clypeal setae. (D) Detail of wings. (E) Metasoma in ventral view. (F) Detail of genitalia in dorsal view. (G, H) Line drawings of fore (G) and hindwings (H) with indication of veins. Abbreviations: AtIII - AtVIII, third through eighth abdominal segments; e = compound eye; fw = forewing; hw = hindwing; md = mandible; Pa = paramere / gonopod; Vo = volsellae. Scale bars, A and B = 2 mm; C and F = 0.2 mm, D, G and H = 1 mm; E = 0.5 mm.</figcaption></figure>

antenna 13-merous; compound eyes very well developed,
bulging; each compound eye with a median notch (hence
kidney-shaped); head broad and flat-rectangular in frontal
view; mesosoma almost as wide as the head (including
compound eyes); metasoma very long, comprising nearly 2
/ 3 of the total length of the body; petiole long and narrow,

with a short and broadly triangular node; gonopods (= par-
ameres) dorsoventrally flattened, hence appearing broadly
lobate in ventral or dorsal view; jugal lobes present.

**Description: Measurements.** Holotype – BL 6.66, HL 0.72, HW 0.57, HWE 1.04, SL 0.28, EL 0.63, WL 1.46, MscL 0.74, MscW 0.58, FWL 5.04, HWL 3.85, PH 0.29,
PL 0.74, GL 3.73, GW 0.93, CI 79.2, HWI 54.8, SI 49.1, OI 87.5, EPI 278, MI 78.3, PI 255.

**Head** (Fig. 1C): Head capsule in lateral view narrow and ovoid-elliptical; in frontal view, head subrectangular; oral region (including clypeus and mouthparts) anteroposteriorly short and weakly projecting from head; malar area obsolete, that is, compound eye contacting pleurostomal margin; postgenal bridge developed and apparently with a posterior projection medially, but encased in bubbles hence length cannot confidently be determined; frontal carinae absent; clypeus almost straight, with short, tapered chaetae in anterior margin. Compound eyes medially notched, hence kidney-shaped; eyes greatly developed and bulging prominently, nearly as long as the head and entirely occupying the head laterally. Ocelli large, median ocellus appearing to be as long or longer than the pedicel; ocellar triangle distant from the compound eyes by apparently at least one median ocellus length. Antennal toruli located just anterad center of head and separated from each other by approximately one or slightly more than one torulus diameter; toruli apparently lacking a distinct medial torular arch, hence appearing convex and subcircular. Antennae 13-merous, very long, equal to total length of body. Antennal scape short, about 3 × as long as broad, but thicker than other flagellomeres. Pedicel somewhat less than 1/2 length of the scape and flattened apparently due to preservation. Mandible long, flat, curved along its length, and bearing two large teeth; basal margin smooth; mandible about 2/3 length of compound eye. Labrum concealed, not visible in frontal view.

**Mesosoma** (Fig. 1A and B; Fig. 2): Mesosoma short, Weber's length about 1/5 of the total body length. Pronotum short and compact. Mesoscutum is broad and somewhat elongated. Notauli absent. Mesoscutellum narrow, raised dorsally, and apparently acutely triangular posteriorly. Mesopleural region broad and bulgingly developed. Propodeum short, difficult to observe due to preservation and angle of amber cut.

**Legs:** Meso- and metatibiae with paired spurs; metatibia clearly with the anterior spur slender and posterior spur thicker and curved. Only claws of left meso- and meta leg well preserved. Arolia not particularly large.

**Forewings** (Fig. 1D and G): Right forewing complete, with preservational curling proximally. **Longitudinal veins.** Costal vein (C) present, extending completely to pterostigma break. Pterostigma well-developed, long, and narrow; rounded proximally and tapering distally; minor break in upper middle edge. Sc + R between 1R and pterostigma about 1/2 pterostigma length. R continuing distad pterostigma slightly past the first marginal cell but ending distant from the forewing apex. 1Rs diverging from Sc + R somewhat close to pterostigma, with this distance being about 2 × its length. 1Rs about 1/3 pterostigma length. M + Cu tubular for its entire length. 1M tubular, weakly curved, and slightly less than twice length of 1Rs. Rs + M tubular and straight, slightly longer than 1R. 2Rs strongly bent. 3Rs about half the length of 2r - Rs. 4Rs tubular and long, meeting R distally. Abscissa of M

between Rs + M and 1m - cu longer than 3Rs but shorter than Rs + M. 2M long and straight, length comparable with 2Rs + 3Rs. 3M significantly longer than 2M, narrowing distally and ending near the forewing apex. 1Cu tubular and well-developed. 2Cu present, meeting A distally; oriented obliquely posterad and comparable in length with 1Cu. 3Cu present, nebulous. Anal vein (A) tubular, length comparable with Sc + R. **Crossveins.** 1r - Rs absent. 2r - Rs present at 1/4 of posterior margin of pterostigma. 2rs - m present. 3rs - m absent. 1m - cu present. 2m - cu absent. Cu - A slightly prefurcal, that is, its anterior terminus is slightly proximad the split of M + Cu. **Cells.** Eight cells are closed: Costal, marginal, first and second submarginal, basal, discal, subbasal, and subdiscal.

**Hindwings** (Fig. 1D and H): Hindwing with six distal hamuli. Jugal lobe present; rounded distally and drop-shaped. **Longitudinal veins.** R tubular. Rs diverging from R-terminus, which starts curved but straight later, narrowing distally. M + Cu splitting well distad crossvein CU - A. Proximal abscissa of M curved anterad, becoming linear and distally oriented gradually, where it meets Rs - M. Cu oriented obliquely downward, essentially straight, narrowing distally. A shallow and straight. **Crossveins.** Cu - A present and prefurcal by about half its length, that is, anterior terminus of Cu - A proximad split of M + Cu. Cu - A slightly longer than the length of Rs - M. **Cells.** Two closed cells: Basal and subbasal. Basal cell with a distinct yet short distal elongation.

**Metasoma** (Fig. 1E and F): Petiole subcylindrical, slender, and elongate (ca. 2.5 times as long as tall), with a short, subtriangular node. Abdominal segment III long, and abdominal segment IV relatively broad. Cinctus (= transverse sulcus) of abdominal tergum and sternum IV

<figure><img src="image_4.png" /><figcaption>**Fig. 2:** Interpretative body drawing of †*Gerontoformica pri-*
*apos* sp.n. in lateral view. Abbreviations: e = compound eye;
ge = genitalia; ppl = propleuron; pnt = pronotum; lb = labrum;
md = mandible.</figcaption></figure>
<figure><img src="image_5.png" /><figcaption>**Fig. 3:** Fossil colony of †*Gerontoformica gracilis* (BARDEN & GRIMALDI, 2014). (A) General view of the fossilized colony fragment of †*Gerontoformica gracilis*, specimen LYU-BM2005; red arrows indicate workers and blue arrow indicates the queen. (B, C) Workers in detailed dorsal and frontal views, respectively. (D, E) The queen in detailed dorsolateral views. Scale bars, A = 2 mm; B - E = 0.5 mm.</figcaption></figure>

apparently absent. Width of other abdominal segments af-
ter abdominal segment IV decreases sequentially, and their
length remains essentially unchanged. Cerci (= pygostyles)
present. Abdominal sternum IX broadly rounded distally.
Gonopods (= parameres) dorsoventrally flattened, lobate
in appearance. Short, straight ciliate setae develop outside
of genitalia and long straight setae present on the volsellae.

†*Gerontoformica gracilis* (BARDEN & GRIMALDI, 2014) (Fig. 3)

**Material:** LYU-BM2005, dealate female (queen), with 3 conspecific workers in syninclusion (Fig. 3A).

Type locality and stratigraphy: Hukawng Valley, Kachin Province, northern Myanmar. Upper Cretaceous, lower Cenomanian (ca. 98.79 ± 0.62 Ma; SHI & al. 2012).
<figure><img src="image_6.png" /><figcaption>**Fig. 4:** Morphological pattern reconstructions of worker (A), queen (B), and male (C) †*Gerontoformica*. The respective proportions of head and gastral measurements are indicated by coloured bars. Abbreviations: EL = compound eyes length; GW = gaster width; HL = head length; HW = head width; MW = mesosoma width.</figcaption></figure>

Housed at the Institute of Geology and Paleontology at Linyi University, Linyi, China.

**Diagnosis** (queen): Identifiable as for the worker (see BOUDINOT & al. 2022a). Compound eye oval-shaped and slightly convex. Scape stout and short, trapezoidal in lateral view. Pedicel elongate and slender, antennomeres III - XII slowly widening in order. Pronotum somewhat elongate. Mesoscutum short and flattened. Petiole long; subpetiolar process small and rounded. Abdominal segment III subtriangular in lateral view; abdominal segment IV most developed and about 3/4 as long as wide.

**Description:** Medium body size specimen. **Measurements:** BL 6.44, HL 0.99, HW 0.67, HWE 0.88, SL 0.41, EL 0.35, WL 2.48, ML 0.75, MW 0.55, PH 0.28, PL 0.78, GL (visible) 2.39, GW 1.27, CI 67.7, SI 61.2, OI 35.3, MI 73.3, PI 279.

**Head** (Fig. 3E): Head capsule smooth and flattened, slightly elongate in lateral view. Frontal carina present. Compound eyes small, oval-shaped and slightly convex. Ocelli present, develop on head crown. Antennae 12-segmented, long and slender. Scape stout and short, trapezoidal in lateral view; maximum width (root) approximately twice minimum width (apex). Pedicel elongate and slender. Antennal flagellomeres III - XII slowly widening in order. Width of the finest segment (flagellomere III) approximately 1/3 of widest segment (flagellomere XII). Details of oral part, and head in frontal view could not be observed due to masking and preventing destroying other worker specimens.

**Mesosoma** (Fig. 3E): Mesosoma long and developed, Weber's length is about 2/5 of total body length; smooth in surface. Pronotum long and strong, elongated into narrow neck. Mesoscutum short and flattened; width approximately 3/4 of length. Mesoscutellum developed, raised dorsally.

**Legs:** Long. Protibiae without spur, but meso- and metatibiae with single long spur. Claws obscured and unobservable. Pro- and mesotibia are slightly shorter than Pro- and mesofemur, but the metatibia as long as metafemur. Tarsomere I very long in each leg, equal to tibia.

**Metasoma** (Fig. 3D): Smooth in surface. Petiole nodular, slender (2.8 times as long as high); with small, rounded ventral projection toward the anterior margin. Abdomen enlarged; abdominal segment III subtriangular in lateral view; abdominal segment IV most developed and about 3/4 as long as wide; abdominal segment III equal to width of widest part in abdominal segment V. Cerci and sting obscured.

## Discussion

### Confident association of winged and wingless females

In the present work, we document for the first time the syninclusion (co-occurrence) of conspecific winged and wingless females in a single piece of amber (Fig. 3). Although previous studies have provided indirect evidence of wingless (“worker”) and winged (“queen”) females among several lineages of stem ants (e.g., PERRICHOT & al. 2008, BARDEN & GRIMALDI 2013, summarized in BOUDINOT & al. 2022a), these were from individuals distributed across several pieces of amber, hence without direct association. Coupled with the discovery of the male †*Gerontoformica priapos sp.n.*, the syninclusion documented here provides the most confident worker-queen association to date and provides a more complete picture of the phenotypic diversity of stem ants (Fig. 4). The females in this amber piece are identifiable as †*Gerontoformica gracilis* (BARDEN & GRIMALDI, 2014) as the cinctus is absent, the petiole is longer than tall, the mesosoma
is narrow and long, and the transverse dorsal sulci are
broad.

Placement of the newly described male

Males may not be the rarest of ant fossils (PERRICHOT
2015, BARDEN & GRIMALDI 2016, BARDEN 2017, BOUDINOT
& al. 2020, 2022a), but most males are not amenable to
taxonomic work because of the pronounced morphological
differences between male and female Formicidae. This
concern casts a shadow over all work on male ants from
the fossil record. Without being able to make confident
male-female associations, it is possible that a parallel
taxonomy develops between the sexes, artificially inflat-
ing the count of species, hence creating both the illusion
of paleodiversity and a nomenclatural problem for future
systematists. Therefore, for the male described herein, we
provide explicit reasoning for our hypothesis of relation-
ship to other Formicidae based on the key to the global
subfamilies of crown Formicidae by BOUDINOT (2015) as
revised by BOUDINOT & al. (2022a) and the recent revision
of †*Gerontoformica* by BOUDINOT & al. (2022b, see pp.
1364, 1380, 1381).

(1) The described male is distinct from the crown
Formicidae at the subfamily level as follows: (a) the ninth
sternum is distally rounded and lacks processes, hence
Dorylinae and Paraponerinae are rejected; (b) the wing ve-
nation is complete, more-or-less matching the groundplan
inferred by BROWN & NUTTING (1950), hence Leptanillinae
is rejected (see also the key and figures to males of this
subfamily by GRIEBENOW 2024); (c) the third abdominal
segment is partially constricted (vs. unconstricted), the
jugal lobe is present (vs. absent), and the mesopectus has
a transverse sulcus (vs. absent), hence excluding Dolicho-
derinae and Formicinae; (d) the third abdominal segment
is not reduced in size and petiolated, hence rejecting Agro-
eomyrmecinae, Myrmicinae, Myrmeciinae, and Pseu-
domyrmecinae; (e) the antennal toruli are distant from
the anterior clypeal margin, the mandibles are bidentate
and falcate (vs. triangular), hence rejecting Proceratiinae;
(f) the prora is not in the form of a transverse lip, exclud-
ing Ectatomminae; (g) the petiole does not have a thin,
elongate peduncle, hence excluding Aneuretinae; (h) the
anterior clypeal margin bears chaetae (thickened setae),
excluding Martialinae; and (i) the helcium is neither broad
lateromedially nor supraaxial, excluding Amblyoponinae.

With all of these character conditions considered to-
gether, the present male may be inferred to be a member
of one of the stem group subfamilies (†Brownimeciinae,
†Haidomyrmecinae, †Sphecomyrminae, †Zigrasimeciinae,
†Armaniinae or the †Camelomecia genus group). Lacking
knowledge of other male stem ants, however, it is not
possible to provide a male-based diagnosis of the crown
Formicidae. We therefore proceed with considering the
described male with respect to other stem group species.
(2) The described male has bidentate, falciform mandibles
and unmodified antennoclypeal complexes, hence is less
likely to be a member of the †Haidomyrmecinae, †Zigra-
simeciinae, or †Camelomecia genus group. (3) Due to its

large, well-developed compound eyes and a long, scarcely
convex petiole, the described male is unlikely to belong
to the †Armaniinae. (4) Among †Brownimeciinae and
†Sphecomyrminae, the posterior clypeal margin does not
extend posteriorly between the antennal toruli, disfavoring
the former subfamily. (5) Among potential †Sphecomyrmi-
nae, the male does not match the male-based genus †Bai-
kuris as: (a) the compound eyes are massive and medially
notched (disfavoring †Baikuris casei GRIMALDI & al. 1997
and †B. ocellantis SOSIAK & al., 2024); (b) the prora does
not appear to be lip-shaped (disfavoring †B. mandibularis
DLUSSKY, 1987 and †B. mirabilis DLUSSKY, 1987); and (c)
the clypeus and malar space do not project from the face
as a narrow process (disfavoring †B. maximus PERRICHOT,
2015). (6) Among female-based taxa of †Sphecomyrminae,
the male matches †Gerontoformica most closely as: (a)
the clypeus is simple, without a median lobe (disfavoring
†Sphecomyrma), and (b) the mandibles are short and tight
fitting against the clypeus (disfavoring †Myanmyrma).
(7) Among known species of †Gerontoformica, the male
most closely matches the †G. pilosa species group as the
cinctus is present and the petiole is longer than tall. (8)
Finally, among species of the †G. pilosa species group,
the described male is most similar to †G. pilosa (BARDEN
& GRIMALDI, 2014) or †G. contega (BARDEN & GRIMALDI,
2014), as the petiole lacks a pronounced anteroventral
process (disfavoring †G. sternorhabda BOUDINOT & al.,
2022) and the body size is not massive (disfavoring †G.
magna (BARDEN & GRIMALDI, 2014)).

Considering the process of exclusion outlined in points
1 - 8 above, we hypothesize that the male described herein
may be a representative of the †*Gerontoformica pilosa* spe-
cies group. Alternatively, the male may belong to another
lineage of stem Formicidae that has yet to be detected. We
recognize the limits of this inference, as the strength relies
on the distinctiveness of the male from the known crown
Formicidae (e.g., BOUDINOT 2015), and the weakness lies
in the lack of knowledge and documentation of males from
stem group lineages of Formicidae. We therefore provide
the described male with the new species name †*Geronto-
formica priapos sp.n.*, with the awareness that this name
could become a junior synonym of another †*Gerontofor-
mica* species. Given that the vast majority of fossil ant taxa
are described from the Cenozoic (ca. 750 species) versus
the Cretaceous (ca. 60 species), we cautiously consider the
description of this male stem ant justifiable, especially as
crown ants are expected to occur before the middle of the
Late Cretaceous at the least (e.g., GRIMALDI & al. 1997,
ROMIGUIER & al. 2022).

Conclusion

The discovery of †*Gerontoformica priapos sp.n.* and a
presumptive colony fragment of †*Gerontoformica* pro-
vides further evidence for the early evolution of ants and
insights into their paleodiversity. The preserved male of
†G. *priapos sp.n.* exhibits distinctive combination of
plesiomorphies and apomorphies, including the bidentate,
falcate mandibles, the clypeal chaetae, and the massive,
medially notched compound eyes. This specimen also provides further evidence for the groundplan wing venation pattern for the Formicidae. Moreover, †G. priapos sp.n. highlights the need to document male ants from the Cretaceous as it is currently not possible to define the crown Formicidae based on males. Most importantly, the presence of both queen and worker ants in a single amber piece provides the first direct evidence of winged-wingless polyphenism among conspecific females.

## Acknowledgements

We thank Mr. De Zhuo for providing the specimens. This study was supported by the National Natural Science Foundation of China (42125201; 42293280), Science Foundation of Yunnan Province (202401CF070193; 202301AS070049; 2015HA021).

## Declaration on use of generative artificial intelligence tools

During the preparation of our manuscript, we utilized generative AI, specifically ChatGPT v.3.5, to enhance the clarity and readability of our text. This involved suggestions for grammatical corrections and improvements to word choice and sentence structure to better convey our findings. While ChatGPT provided initial recommendations, all content was thoroughly reviewed and modified by the authors to ensure accuracy and alignment with the manuscript's intent. The authors take full responsibility of the content of the manuscript in every detail.

## Conflict of interest

The authors declare that they have no conflict of interest.

## References

ALLARD, D., GOBIN, B., ITO, F., TSUJI, K. & BILLEN, J. 2002: Sperm transfer in the Japanese queenless ant *Diacamma* sp. (Hymenoptera: Formicidae). – Netherlands Journal of Zoology 52: 77-86.

BAER, B. & BOOMSMA, J.J. 2006: Mating biology of the leaf-cutting ants *Atta colombica* and *A. cephalotes*. – Journal of Morphology 267: 1165-1171.

BARDEN, P. 2017: Fossil ants (Hymenoptera: Formicidae): ancient diversity and the rise of modern lineages. – Myrmecological News 24: 1-30.

BARDEN, P., BOUDINOT, B.E. & LUCKY, A. 2017: Where fossils dare and males matter: Combined morphological and molecular analysis untangles the evolutionary history of the spider ant genus *Leptomyrmex* MAYR (Hymenoptera: Dolichoderinae). – Invertebrate Systematics 31: 765-780.

BARDEN, P. & GRIMALDI, D. 2013: A new genus of highly specialized ants in Cretaceous Burmese amber (Hymenoptera: Formicidae). – Zootaxa 3681: 405-412.

BARDEN, P. & GRIMALDI, D. 2016: Adaptive radiation in socially advanced stem-group ants from the Cretaceous. – Current Biology 26: 515-521.

BARDEN, P., PERRICHOT, V. & WANG, B. 2020: Specialized predation drives aberrant morphological integration and diversity in the earliest ants. – Current Biology 30: 3818-3824.

BOOMSMA, J.J., BAER, B. & HEINZE, J. 2005: The evolution of male traits in social insects. – Annual Review of Entomology 50: 395-420.

BOUDINOT, B.E. 2015: Contributions to the knowledge of Formicidae (Hymenoptera, Aculeata): a new diagnosis of the family, the first global male-based key to subfamilies, and a treatment of early branching lineages. – European Journal of Taxonomy 120: 1-62.

BOUDINOT, B.E. 2024: Ant evolution: amber revelations of extinction, survival and recovery. – Current Biology 34: 318-320.

BOUDINOT, B.E., MOOSDORF, O.T.D., BEUTEL, R.G. & RICHTER, A. 2021: Anatomy and evolution of the head of *Dorylus helvolus* (Formicidae: Dorylinae): patterns of sex- and caste-limited traits in the sausagefly and the driver ant. – Journal of Morphology 282: 1616-1658.

BOUDINOT, B.E., PERRICHOT, V. & CHAUL, J.C.M. 2020: †*Camelosphecia* gen. nov., lost ant-wasp intermediates from the mid-Cretaceous (Hymenoptera, Formicoidea). – ZooKeys 1005: 21-55.

BOUDINOT, B.E., RICHTER, A., HAMMEL, J., SZWEDO, J., BOJARSKI, B. & PERRICHOT, V. 2022b: Genomic-phenomic reciprocal illumination: *Desyopone hereon* gen. et sp. nov., an exceptional aneuretine-like fossil ant from Ethiopian amber (Hymenoptera: Formicidae). – Insects 13: art. 796.

BOUDINOT, B.E., RICHTER, A., KATZKE, J., CHAUL, J., KELLER, R., ECONOMO, E., BEUTEL, R. & YAMAMOTO, S. 2022a: Evidence for the evolution of eusociality in stem ants and a systematic revision of †*Gerontoformica* (Hymenoptera: Formicidae). – Zoological Journal of the Linnean Society 195: 1355-1389.

BOUDINOT, B.E., WACHKOO, A.A. & BHARTI, H. 2016: The first ergatoid male of *Platythyrea* (Hymenoptera: Formicidae: Ponerinae), with contribution to colony labor suggested by observation and comparative morphology. – Myrmecological News 22: 59-64.

BROWN, W.L. & NUTTING, W.L. 1950: Wing venation and the phylogeny of the Formicidae. – Transactions of the American Entomological Society 75: 113-132.

CAO, H., BOUDINOT, B.E., SHIH, C., REN, D. & GAO, T. 2020: Cretaceous ants shed new light on the origins of worker polymorphism. – Science China Life Sciences 63: 1085-1088.

DLUSSKY, G.M. 1999: The first find of the Formicoidea (Hymenoptera) in the Lower Cretaceous of the Northern Hemisphere. – Paleontologicheskii Zhurnal 3: 62-66.

GRIEBENOW, Z. 2024: Systematic revision of the ant subfamily Leptanillinae (Hymenoptera, Formicidae). – ZooKeys 1189: 83-184.

GRIMALDI, D., AGOSTI, D. & CARPENTER, J.M. 1997: New and rediscovered primitive ants (Hymenoptera: Formicidae) in Cretaceous amber from New Jersey, and their phylogenetic relationships. – American Museum Novitates 3208: 1-43.

GUO, Y., SHIH, C., ZHUO, D., REN, D., ZHAO, Y. & GAO, T. 2021: The first queen-worker association for Cretaceous Formicidae: the winged caste of *Haidomyrmex cerberus*. – ZooKeys 1048: 69-78.

HELMS, J.A. 2018: The flight ecology of ants (Hymenoptera: Formicidae). – Myrmecological News 26: 19-30.

HÖLDOBLER, B. 1966: Futterverteilung durch Männchen im Ameisenstaat. – Zeitschrift für vergleichende Physiologie 52: 430-455.

HÖLDOBLER, B. & BARTZ, S.H. 1985: Sociobiology of reproduction in ants. In: HÖLDOBLER, B. & LINDAUER, M. (Eds.): Experimental behavioral ecology and sociobiology. – Gustav Fischer, Stuttgart, pp. 237-257.

HÖLDOBLER, B. & WILSON, E.O. 1990: The ants. – Harvard University Press, Cambridge, MA, 732 pp.

JOUAULT, C., CONDAMINE, F.L., LEGENDRE, F. & PERRICHOT, V. 2024: The angiosperm terrestrial revolution buffered ants against extinction. – Proceedings of the National Academy of Sciences of the United States of America 121: art. e2317795121.
KELLER, R.A., PEETERS, C. & BELDADE, P. 2014: Evolution of thorax architecture in ant castes highlights trade-off between flight and ground behaviors. - *Elife* 3: art. e01539.

KIKUTA, N. & TSUJI, K. 1999: Queen and worker policing in the monogynous and monandrous ant, *Diacamma* sp. - Behavioral Ecology and Sociobiology 46: 180-189.

KINOMURA, K. & YAMAUCHI, K. 1987: Fighting and mating behaviors of dimorphic males in the ant: *Cardiocondyla wroughtoni*. - *Journal of Ethology* 5: 75-81.

LACH, L., PARR, C. & ABBOTT, K. 2010: Ant ecology. - Oxford University Press, Oxford, UK, 402 pp.

LAPOLLA, J.S. 2005: Ancient trophophores: a fossil *Acropyga* (Hymenoptera: Formicidae) from Dominican amber. - *Transactions of the American Entomological Society* 131: 21-28.

LAPOLLA, J.S., DLUSSKY, G.M. & PERRICHOT, V. 2013: Ants and the fossil record. - *Annual Review of Entomology* 58: 609-630.

MACGOWN, J.A., BOUDINOT, B.E., DEYRUP, M. & SORGER, D.M. 2014: A review of the Nearctic *Odontomachus* (Hymenoptera: Formicidae: Ponerinae) with a treatment of the males. - *Zootaxa* 3802: 515-552.

METZLER, S., HEINZE, J. & SCHREMPF, A. 2016: Mating and longevity in ant males. - *Ecology and Evolution* 6: 8903-8906.

MOSER, J.C., REEVE, J.D., BENTO, J.M.S., DELLA LUCIA, T.M., CAMERON, R.S. & HECK, N.M. 2004: Eye size and behaviour of day-and night-flying leafcutting ant alates. - *Journal of Zoology* 264: 69-75.

NEL, A., PERRAULT, G., PERRICHOT, V. & NÉRAUDEAU, D. 2004: The oldest ant in the Lower Cretaceous amber of Char-ente-Maritime (SW France) (Insecta: Hymenoptera: Formi-cidae). - *Geologica Acta* 2: 23-29.

OGATA, K., MURAI, K., YAMAUCHI, K., & TSUJI, K. 1996: Size differentiation of copulatory organs between winged and wingless reproductives in the ant *Technomyrmex albipes*. - *Naturwissenschaften* 83: 331-333.

PEETERS, C. & ITO, F. 2001: Colony dispersal and the evolution of queen morphology in Hymenoptera. - *Annual Review of Entomology* 46: 601-630.

PEETERS, C. & MOLET, M. 2010: Colonial reproduction and life histories. In: LACH, L., PARR, C. & ABBOT, K.L. (Eds.): Ant Ecology. - Oxford University Press, Oxford, UK, pp. 159-176.

PERRICHOT, V. 2015: A new species of *Baikuris* (Hymenoptera: Formicidae: Sphecomyrminae) in mid-Cretaceous amber from France. - *Cretaceous Research* 52: 585-590.

PERRICHOT, V., BANG, B. & ENGEL, M.S. 2016: Extreme mor-phogenesis and ecological specialization among Cretaceous basal ants. - *Current Biology* 26: 1468-1472.

PERRICHOT, V., BOUDINOT, B.E., ENGEL, M.S., XU, C., BOJARSKI, B. & SZWEDO, J. 2022: Ants (Hymenoptera: Formicidae) from Miocene Ethiopian amber: filling gaps in the geological record of African terrestrial biota. - *Zoological Journal of the Linnean Society* 196: 775-791.

PERRICHOT, V., NEL, A., NÉRAUDEAU, D., LACAU, S. & GUYOT, T. 2008: New fossil ants in French Cretaceous amber (Hymeno-ptera: Formicidae). - *Naturwissenschaften* 95: 91-97.

PERRICHOT, V., WANG, B. & BARDEN, P. 2020: New remarkable hell ants (Formicidae: Haidomyrmecinae stat. nov.) from mid-Cretaceous amber of northern Myanmar. - *Cretaceous Research* 109: art. 104381.

RADCHENKO, A.G. & ELMES, G.W. 2010: *Myrmica* ants (Hymeno-ptera: Formicidae) of the Old World. Fauna Mundi 3. - *Natura Optima Dux Foundation, Warsaw, 790 pp.*

RICHTER, A., BOUDINOT, B.E., YAMAMOTO, S., KATZKE, J. & BEUTEL, R. 2022: The first reconstruction of the head anatomy of a Cretaceous insect, †*Gerontoformica gracilis* (Hymeno-

ptera: Formicidae), and the early evolution of ants. - Insect Systematics and Diversity 6: art. 4.

ROMIGUIER, J., BOROWIEC, M.L., WEYNA, A., HELLEU, Q., LOIRE, E., LA MENDOLA, C., RABELING, C., FISHER, B., WARD, P. & KELLER, L. 2022: Ant phylogenomics reveals a natural selection hotspot preceding the origin of complex eusociality. - *Current Biology* 32: 2942-2947.

SHI, G., GRIMALDI, D., HARLOW, G., WANG, J., WANG, J., YANG, M., LEI, W., LI, Q. & LI, X. 2012: Age constraint on Burmese amber based on U-Pb dating of zircons. - *Cretaceous Research* 37: 155-163.

SHIK, J.Z., FLATT, D., KAY, A. & KASPARI, M. 2012: A life history continuum in the males of a Neotropical ant assemblage: refuting the sperm vessel hypothesis. - *Naturwissenschaften* 99: 191-197.

SOSIAK, C., COCKX, P., SUAREZ, P.A., MCKELLAR, R. & BARDEN, P. 2024: Prolonged faunal turnover in earliest ants revealed by North American Cretaceous amber. - *Current Biology* 34: 1755-1761.

SZWEDO, J., WANG, B., SOSZYNSKA, A., AZAR, D. & ROSS, A. 2020: International Palaeoentomological Society Statement. - *Palaeoentomology* 3: 221-222.

ULMER, J.M., MIKÓ, I., RICHTER, A., HELMS, A., VAN DE KAMP, T. & KROGMANN, L. 2023: 'Social glands' in parasitoids? - convergent evolution of metapleural glands in Hymeno-ptera. - Insect Systematics and Diversity 7: art. 2.

WHEELER, W.M. 1910: Ants: their structure, development and behavior (Vol. 9). - Columbia University Press, New York, NY, 663 pp.

WILSON, E.O. 1953: The origin and evolution of polymorphism in ants. - *The Quarterly Review of Biology* 28: 136-156.

WILSON, E.O. 1984: Tropical social parasites in the ant genus *Pheidole*, with an analysis of the anatomical parasitic syndrome (Hymenoptera: Formicidae). - *Insectes Sociaux* 31: 316-334.

WILSON, E.O., CARPENTER, F.M. & BROWN, W.L. 1967: The first Mesozoic ants, with the description of a new subfamily. - *Psyche* 74: 6-10.

YAMAUCHI, K., KIMURA, Y., CORBARA, B., KINOMURA, K. & TSUJI, K. 1996: Dimorphic ergatoid males and their reproductive behavior in the ponerine ant *Hypoponera bondroiti*. - *Insectes Sociaux* 43: 119-130.

YOSHIMURA, M. & FISHER, B.L. 2007: A revision of male ants of the Malagasy region (Hymenoptera: Formicidae): key to subfamilies and treatment of the genera of Ponerinae. - *Zootaxa* 1654: 21-40.

YOSHIMURA, M. & FISHER, B.L. 2012: A revision of the Malagasy endemic genus *Adetomyrma* (Hymenoptera: Formicidae: Amblyoponinae). - *Zootaxa* 3341: 1-31.

YU, T., KELLY, R., LIN, M., ROSS, A., KENNEDY, J., BROLY, P., XIA, F., ZHANG, H. & DILCHER, D. 2019: An ammonite trapped in Burmese amber. - *Proceedings of the National Academy of Sciences of the United States of America* 116: 11345-11350.

ZHUANG, Y., LIU, Y., RAN, H., JARZEMBOWSKI, A.E. & ZHANG, Q. 2024: A new species and one new wing type of the iron maiden ants from Kachin amber (Hymenoptera: Formicidae: *Zigrasimecia*). - *Cretaceous Research* 154: art. 105742.

ZHUANG, Y., RAN, H., LI, X., FENG, C. & LIU, Y. 2022: A new species of the iron maiden ant based on an alate female from mid-Cretaceous Burmese amber (Hymenoptera: Formicidae: †*Zigrasimecia*). - *Cretaceous Research* 130: art. 105056.