Messor species

Orou, Noel, Csősz, Sándor, Arnan, Xavier, Pol, Rodrigo G., Arthofer, Wolfgang, Schlick-Steiner, Birgit C. & Steiner, Florian M., 2023, Messor erwini sp. n., a hitherto cryptic harvester ant in the Iberian Peninsula, Zoologischer Anzeiger 307, pp. 36-53 : 50-51

5.2. Formal descriptions of Iberian Messor species (alphabetic order)

5.2.1. Messor barbarus

( Fig. 8A–J , Table S1, Table 7)

Relatively large species; Head size (CS) 1738 μm [926, 3106]. Color: minor workers concolorous; major workers bicolored: head color dark reddish, tone lighter than that of mesosoma and gaster.

Head: Ground surface smooth, or shagreened, shiny. Head of minor workers often without rugae and rugulae. In major workers postocular surface smooth, or shagreened, shiny, rugae and rugulaeabsent, the preocular head dorsum, genae, and frontal carinae inconspicuously rugulose. Surface around the antennal sockets with concentric rugulae. Anterior clypeal border conspicuously dentate. Clypeus longitudinally costulate, posterior third of clypeus often without costulae. Ground surface smooth or shagreened. Median clypeal costa conspicuous. Frontal triangle inconspicuously sculptured, ground surface smooth, or feebly shagreened, shiny; in major workers lateral parts inconspicuously striate, medially smooth, shiny. In both subcastes median clypeal costa does not surpass the clypeal-frontal triangular border. Psammophore absent, only straight or C-shaped hairs present posterior to buccal cavity. Basal scape lobe well-developed (ScBaC/CS 0.045 [0.037, 0.054]), having an acute projection externally.

Mesosoma: feebly sculptured. In minor workers dorsum of pronotum shagreened and shiny, sides shagreened; in major workers dorsum and upper sides of pronotum shagreened, shiny, ventral-most part of the propleuron inconspicuously sculptured, irregularly rugulose, ground surface shagreened, shiny. Mesonotum in minor workers smooth or shagreened, shiny, the ventral-most part of the mesopleuron inconspicuously rugulose transversally; in major workers mesonotum shiny, mesopleuron transversally rugulose, ground surface shagreened, shiny. Propodeum in minor workers smooth or shagreened, shiny, sometimes inconspicuously rugulose; in major workers dorsum and sides transversally, and symmetrically rugose. In both subcastes propodeum rounded in profile.

Petiole and Postpetiole: Petiolar node with numerous pairs of long (200–400 μm) hairs. Sides of peduncle with a pair of standing setae longer than 100 μm (100–150 μm).

5.2.1.1. Messor bouvieri . ( Fig. 9A–J , Table S1, Table 7)

Relatively small species; Head size (CS) 1400 μm [899, 1832]. Color: minor and major workers concolorous brown to black.

Head: Ground surface smooth, or shagreened. Head of minor workers often without rugae and rugulae; in major workers rugae and rugulaeon head dorsum and postocular sides absent or inconspicuous, ground surface shagreened, dull, sides, genae, and frontal carinae feebly rugulose. Surface around the antennal sockets with concentric rugulae. Anterior clypeal border edentate. Clypeus irregularly sculptured, rugulose, or roguloso-reticulate, ground surface shagreened, dull. Median clypeal costa absent. Frontal triangle longitudinally feebly costulate, ground surface between costulae smooth, or shagreened. Psammophore, i.e. several pairs of long, J-shaped hairs, posterior to buccal cavity present. Basal scape lobe weekly developed (ScBaC/CS mean 0.031 [0.025, 0.036]), without acute projection externally.

Mesosoma: Feebly sculptured. Pronotum ground surface shagreened, dull. Sides irregularly rugulose. Mesonotum inconspicuously transversally rugulose, ground surface shagreened, dull. Propodeum transversally, rugulose, ground surface shagreened, dull. Propodeum angulate in profile but does not bear a pair of propodeal tubercles.

Petiole and Postpetiole: Petiolar node without standing setae. Sides of peduncle with a few pairs of standing setae which are no longer than 100 μm (40–80 μm).

5.2.1.2. Messor capitatus . ( Fig. 10A–J , Table S1, Table 7)

Relatively large species; Head size (CS) 1787 μm [936, 3520]. Color: minor and major workers concolorous brown to black.

Head: Ground surface smooth, or shagreened. Head of minor workers often without rugae and rugulae; in major workers rugae and rugulae on head dorsum and postocular sides inconspicuous, ground surface smooth, or shagreened, shiny, sides, genae, and frontal carinae conspicuously rugulose, or rugose. Surface around the antennal sockets with concentric rugulae. Anterior clypeal border conspicuously dentate. Clypeus longitudinally costulate, posterior third of clypeus often without costulae. Ground surface smooth or shagreened. Median clypeal costa conspicuous.

Frontal triangle inconspicuously sculptured. Ground surface smooth, shagreened; in major workers lateral parts irregularly striate, medially smooth. In both subcastes median clypeal costa does not surpass the clypeal-frontal triangular border. Psammophore absent, only straight or C-shaped hairs present posterior to buccal cavity. Basal scape lobe well-developed (ScBaC/ CS 0.041 [0.032, 0.053]), having an acute projection externally .

Mesosoma: feebly sculptured. In minor workers dorsum of pronotum shagreened and moderately shiny, sides shagreened; in major workers dorsum and upper sides of pronotum shagreened, feebly rugulose, ventral-most part of the propleuron inconspicuously sculptured, irregularly rugulose, ground surface shagreened, dull. Mesonotum dorsum and mesopleuron in both subcastes transversally rugose, ground surface punctate or shagreened, dull. Propodeum dorsum and sides in minor workers with very feeble transversal rugulae, ground surface shagreened, moderately shiny sometimes asymmetrically rugose, in major workers dorsum and sides transversally, and symmetrically rugose. Propodeum in minor workers rounded in profile; in major workers propodeum angulate with a pair of propodeal tubercles, which are dentiform in the largest workers i.e. sharp longitudinal ridges on the dorsum of propodeal tubercles absent.

Petiole and postpetiole: Petiolar node with numerous pairs of long (200–400 μm) hairs. Sides of peduncle with a pair of standing setae longer than 100 μm (100–150 μm).

5.2.1.3. Messor erwini sp. n.. ( Fig. 11A–J , Table S1, Table 7)

Holotype: SPAIN: Castellbell i el Vilar, 41.652909, 1.849238, open and heterogeneous shrubland, June 2018, leg. X. Arnan & R. G. Pol, Collection code #19603. Major worker (Natural History Museum Vienna).

Paratypes: SPAIN: Castellbell i el Vilar, 41.652909, 1.849238, open and heterogeneous shrubland, June 2018, leg. X. Arnan & R. G. Pol, Collection codes #19595, #19597, #19598, #19600, #19601, #19602, #19603, #19604, #19639, #19640, #19641, #19642, #19643, #19645; July 2018, leg. X. Arnan & R. G. Pol, Collection codes #19596, #19599, #19644, #19646. In total, 58 major and minor workers ( Hungarian Natural History Museum Budapest , National Museum of Natural History Paris , National Museum of Natural Sciences Madrid, Natural History Museum Basel , Natural History Museum Vienna , private collection of S´andor Csosz ˝) .

Etymology: The species is dedicated to Erwin Meyer, wholehearted researcher and teacher of arthropods at the University of Innsbruck for many years, who is greatly missed for his humor, his enthusiasm, and his ability to motivate and to touch hearts.

The largest of the four species analyzed in this study; Head size ( CS) 2072 μm [1150, 3490]. Color: minor and smaller major workers concolorous; the largest major workers bicolored: color of head dorsum lighter than head sides, mesosoma and gaster.

Head: Ground surface smooth, or shagreened. In minor workers head often without rugae and rugulae, genae and frons with feeble rugulae, postocular area smooth or shagreened, shiny; in major workers sides, genae, and frontal carinae conspicuously rugulose, or rugose, postocular surface smooth or shagreened, shiny; in the largest major workers postocular part can be inconspicuously rugulose. Surface around the antennal sockets with concentric rugulae. Anterior clypeal border conspicuously dentate. Clypeus longitudinally costulate across the whole area of the clypeus, ground surface smooth or shagreened. Median clypeal costa well-developed and conspicuous. Frontal triangle conspicuously sculptured. Ground surface smooth, or shagreened. In both subcastes the median clypeal costa always runs across the frontal triangle uninterrupted from the base to the apex; in minor workers only the median costa is conspicuous; in major workers often a number of well-developed clypeal costae present on the frontal triangle. Psammophore absent, only straight or C-shaped hairs present posterior to buccal cavity. Basal scape lobe well-developed (ScBaC/ CS 0.051 [0.033, 0.063]), having an acute projection externally.

Mesosoma: coarsely sculptured. In minor workers dorsum of pronotum smooth and shiny, sides smooth, or shagreened, ventral-most part inconspicuously rugulose; in major workers dorsum and propleuron inconspicuously sculptured, longitudinally rugose; in largest major workers rugae and rugulaeconspicuous, ground surface shagreened. Mesonotum dorsum and mesopleuron in both subcastes transversally rugose, ground surface punctate or shagreened, dull. Propodeum dorsum and sides transversally, sometimes asymmetrically rugose. Propodeum in minor workers rounded in profile; in major workers propodeum angulate with a pair of propodeal tubercles, which are dentiform or lamelliform in the largest workers, i.e. sharp longitudinal ridges on the dorsum of propodeal tubercles may present.

Petiole and Postpetiole: Petiolar node with numerous pairs of long (200–400 μm) hairs. Sides of peduncle with a pair of standing setae longer than 100 μm (100–150 μm).

Funding

Fieldwork was funded by the Minist´erio de Ciencia, Innovacion´y

Universidades (grant number RYC-2015-18448).

Figures

Fig. 8. Messor barbarus major (A, C, E, G, H; collection code #19610) and minor (B, D, F, I, J; collection code #19612) workers. Lateral view of body (A, B); dorsal view of body (C, D); head in full-face view (E, F); frontal triangle in larger magnification (G, I); lateral view of petiole in larger magnification (H, J).

Fig. 9. Messor bouvieri major (A, C, E, G, H; collection code #19624) and minor (B, D, F, I, J; collection code #19620) workers. Lateral view of body (A, B); dorsal view of body (C, D); head in full-face view (E, F); frontal triangle in larger magnification (G, I); lateral view of petiole in larger magnification (H, J).

Fig. 10. Messor capitatus major (A, C, E, G, H; collection code #19646) and minor (B, D, F, I, J; collection code #19643) workers. Lateral view of body (A, B); dorsal view of body (C, D); head in full-face view (E, F); frontal triangle in larger magnification (G, I); lateral view of petiole in larger magnification (H, J).

Fig. 11. Messor erwini sp. n. major (A, C, E, G, H; holotype; collection code #19603e) and minor (B, D, F, I, J; paratype; collection code #19603d) workers. Lateral view of body (A, B); dorsal view of body (C, D); head in full-face view (E, F); frontal triangle in larger magnification (G, I); lateral view of petiole in larger magnification (H, J).