Monomorium emarginatum DuBois 1986

Seifert, Bernhard, 2025, The Monomorium carbonarium species group in the Nearctic and Europe (Hymenoptera: Formicidae), Soil Organisms (Toronto, Ont.) 97 (1), pp. 55-84 : 77-78

Monomorium emarginatum DuBois 1986

[type investigation]

This species has been described on males, gynes and workers from near Amissville in Virginia. Investigated were the holotype winged gyne labelled “ 2mi w Amissville Rappahannock Co. ”, VIGINIA June 21, 1957 W. L.Brown E.O. Wilson ”, “M.C.Z. Holotype 32922”, “ Monomorium emarginatum Holotype M. DuBois 1983”; One paratype winged gyne and 3 paratype workers on the same pin labelled “ Brewster C.Cod P. rig. and oak on sand”, “Mass. VIII.4. 1955 W. L.Brown ”, “M.C.Z. Paratype 32922”, “ Monomorium emarginatum Paratype M. DuBois 1983”; depository MCZ Cambridge. All material examined. Numeric phenotypical data were taken in 9 samples with 30 workers and three winged gynes. For details see supplementary information SI1, SI2, SI3. All this material originated from the USA .

Geographic range. Apparently widely distributed in the USA. Vouchers are from the states New York, Pennsylvania, Maine, Massachusetts, Maryland, Virginia, North Dakota, Utah and New Mexico from sea level up to 2044 m in New Mexico .

Diagnosis: --Worker ( Tab. 2, Figs. 19-20, key). Very small, CS 460 ± 25 µm. Head rather short, CL/CW 1.180 ± 0.026. Dents on clypeal margin moderately long (ExCly/ CS 4.20 ± 0.75%), not very acute and rather widely distant (ClSpD/CS 9.99 ± 0.93%). Frons moderately wide and frontal carinae only very slightly diverging frontad (FL/ FR 1.039 ± 0.24, FL/CS 0.269 ± 0.008, FR/CS 0.259 ± 0.009). Eye large and preocular distance moderately large (EL/CS 0.217 ± 0.008, PrOc/CS 0.223 ±0.009). Scape and 3 rd funiculus segment very short (SL/CS 0.757 ± 0.014, Fu2/CS 5.67 ± 0.27%, Fu3/CS 4.22 ± 0.29%). Mesosoma relatively short and relatively wide (ML/CS 1.181 ± 0.035, MW/CS 0.583 ± 0.015). Metanotal groove moderately deep, MGr/CS 4.49 ± 0.74%. Dorsal and caudal profile of propodeum not meeting in an angle, as a whole more or less convex. Petiole narrow, short and low (PeW/CS 0.267 ± 0.014, PeL/CS 0.406 ±0.015, PeH/CS 0.344 ± 0.011). Postpetiole moderately wide but very low (PpW/CS 0.296 ± 0.013, PpH/CS 0.260 ± 0.010). Lateral area of mesopleuron smooth. Head, mesosoma and gaster dark brown to brown; mandibles and lateral clypeus yellow brown.

--Gyne ( Tab. 4): Only winged gynes are known. Rath- er large (CS 807 ± 15 µm). Very short head, scape and petiole (CL/CW 0.978 ±0.021, SL/CS 0.704 ± 0.021, PEL/CS 0.613 ± 0.015). The short median furrow on posterior mesonotum, called diagnostic by DuBois (1986), is occasionally also found in other species.

Taxonomic comments. The worker is comparatively easy to recognize as a combination of the characters underlined above. With all measurements given in mm, the three gynes are separable from the 24 winged gynes of other species by the discriminant 48.34*SL+34.27*PpW- 35.905*CW-4.336PeL-12.723 <0.

Biology. Largely unknown. Alate winged gynes were observed in the nests 21 June 1957 (Amissville), 3 August 2000 (Androscoggin), 4 August 1955 (Cape Cod). The colony from Androscoggin / Maine was found as a “crater nest in fine sand on an open spot with sparse vegetation within a Bracken Wintergreen stand” (S. Cov- er). The workers from Green Canyon / Utah were found “on blossoming Cirsium lanceolatum ” (G.F.Knowlton) .

Monomorium lorenzoi n.sp.

Etymology: dedicated to the collector Lorenzo Fraysse. Type material. Holotype plus two paratype workers on the same pin labelled “ USA: 32.83908, -117.04528, 85 m Mission Trail Park, sandy river bank, riparian vegetation, L. Fraysse 2024.03.22 -3569”

All material examined. Only the type sample was available. For details see supplementary information SI1, SI2. Geographic range. Only the type locality is known.

Description: --Worker ( Tab. 2, Figs. 27 , 28, key). Very small, CS 454 ± 5 µm. Head elongated, CL/CW 1.248 ± 0.014. Dents on clypeal margin moderately long (ExCly/CS 4.08 ± 0.17%), not very acute and widely distant (ClSpD/CS 11.03 ± 0.66%). Frons very narrow and frontal carinae only very slightly diverging frontad (FL/FR 1.028 ± 0.25, FL/ CS 0.247 ± 0.009, FR/CS 0.240 ± 0.008). Eye larger than in other species and preocular distance moderately large (EL/CS 0.225 ± 0.005, PrOc/CS 0.214 ±0.003). Scape and 3 rd funiculus segment long (SL/CS 0.843 ± 0.012, Fu2/CS 6.35 ± 0.37%, Fu3/CS 5.27 ± 0.21%). Mesosoma moderately long but very narrow (ML/CS 1.186 ± 0.009, MW/CS 0.537 ± 0.002). Metanotal groove moderately deep, MGr/CS 4.80 ± 0.35%. Dorsal and caudal profile of propodeum forming an angle of 140°. Petiole narrow, extremely short and very low (PeW/CS 0.265 ± 0.012, PeL/CS 0.386 ±0.003, PeH/CS 0.334 ± 0.008). Postpetiole moderately wide and low (PpW/CS 0.306 ± 0.011, PpH/CS 0.272 ± 0.015). All surfaces of head, mesosoma and gaster glabrous with exception few longitudinal carinulae on lateral parts of frontal lobes, lateral parts of clypeus, ventrolateral metapleuron and caudolateral mesopleuron (continuing dorsad into the metanotal groove). Head, mesosoma and gaster black; mandibles and lateral clypeus yellow brown.

--Gyne: unknown.

Taxonomic comments. The combination of the characters underlined above is diagnostic. The description of a new species based on a single nest sample appears justified because of all three specimens represent a combination of extreme character expressions. A simple index of three shape variables FL/CS * PeL/CS / (EL/CS) is 0.425 ± 0.004 [0.422, 0.430] in the types of M. lorenzoi n.sp. but 0.604 ± 0.052 [0.449,0.765] in 400 specimens of all other species. The hypothesis that the type sample of M. lorenzoi n.sp. could represent nothing but a simple monogenous mutant of the abundant species M. ergatogyna appears unlikely because the three shape variables, representing different body parts, are not cor- related in 83 workers of the latter species. The mean Pearson’s correlation coefficient between the three variables is in M. ergatogyna 0.089 ± 0.033 – for comparison this coefficient is in the same sample 0.752 between PeW/CS and PpW/CS, 0.696 between FL/CS and FR/CS or 0.601 between Fu2/CS and Fu3/CS.

Biology. The few specimens were collected foraging on very low vegetation immediately around the nest entrance. The latter was a very small hole in the ground (<1mm of diameter) without any soil ejections around, in thin but very compacted ferruginous sand (on a welltrodden path). The micro-habitat was the path delimiting a low riparian vegetation from a drier grassland.

Monomorium monomorium Bolton 1987

Figures

Figure 27. Head of Monomorium compressum, paratype wingless gyne; Mexico: Hidalgo: San Miguel