max_devis's Journal

This post will serve as a clarification on the taxonomic status of Leptogenys sp. 1 (Maschwitz et al., 1989) and Leptogenys distinguenda (Emery, 1887) and the use of these names on iNaturalist. The conclusions presented here were made by me and @clurarit after a brief literature review and comparison of online available specimens and iNaturalist observations.

Maschwitz et al. (1989) was the first study to report on Leptogenys sp. 1, which they described as an undescribed species of the L. processionalis group that morphologically resembles L. mutabilis. The species displays a remarkable degree of convergent evolution with doryline army ants, having a nomadic lifestyle and foraging only through mass raids. In a subsequent work, Maschwitz & Steghaus-Kovac (1991) noted the following:

This species, which was initially described in [Maschwitz et al. (1989)] as Leptogenys sp. 1 near mutabilis, could be identified as L. distinguenda through comparisons with the collection of W. L. Brown, Jr., Cornell University, and the collection of the Museum of Comparative Zoology, Harvard, which was made available to him for this purpose. Specimens of this and the other Leptogenys species listed in the text are deposited in the Brown collection and in the Natural History Museum, London, under the reference numbers given in this text. As W. L. Brown's planned revision of the Ponerini is currently still in preparation, most of the identifications are still provisional.

Hence, later studies on the same species at the Field Studies Centre of the University Malaya in Ulu Gombak, Malaysia, all referred to it as L. distinguenda (Witte & Maschwitz, 2000; Witte & Maschwitz, 2002; Witte et al., 2008; Witte et al., 2009; Maruyama et al., 2010; von Beeren et al., 2010). However, Brückner et al. (2017) wrote the following:

Note that the host ant is an undescribed species (K Arimoto, pers. comm., 2017). It was designated previously as Leptogenys sp. 1 (Maschwitz et al., 1989) and as L. distinguenda (see Maschwitz & Steghaus-Kovac, 1991; Witte & Maschwitz, 2000; Witte & Maschwitz, 2002; Witte et al., 2008; von Beeren et al., 2011a). To be consistent with the most recent publications we use the name Leptogenys distinguenda for the species, which is in fact a nomen nudum. Specimen images of L. distinguenda have been published previously (denoted there as L. distinguenda (Maruyama et al., 2010)).

However, it is unclear why L. distinguenda should be a nomen nudum. While short, the description by Emery (1887) is not unusual for its time, and actually mentions several important diagnostic characters accompanied by a drawing. In particular, the absence of a basal tooth on the mandible and the rounded clypeal lobe indicate an affinity with L. processionalis and L. birmana, while setting it apart from L. mutabilis and L. iridescens. Emery was clearly aware of the importance of these characters, contrasting it to the situation in L. mutabilis. The syntype of Lobopelta distinguenda on antweb matches this description. On iNaturalist, there are a number of observations from Borneo that seem like a good match for this taxon (e.g., https://www.inaturalist.org/observations/263692167).

However, there are several indications that Leptogenys sp. 1 is not conspecific with L. distinguenda sensu Emery (1887). Mainly, the specimen images shown by Maruyama et al. (2010) clearly show a different species. The specimen has a well-developed basal tooth on the mandible, truncate clypeal lobe, and completely smooth dorsal head surface, indicating a close affinity to L. mutabilis and L. iridescens. Notably, the initial description of Leptogenys sp. 1 by Maschwitz et al. (1989) also mentioned the resemblance to mutabilis. Assuming that Maruyama et al. did indeed study the same species as Maschwitz and Witte (which is the case according to the study), this would mean that Leptogenys sp. 1 is distinct from distinguenda and thus remains undescribed. iNaturalist observations seem to support this conclusion, since there are several observations in the vicinity of Kuala Lumpur (where the Field Studies Centre is located) that strongly resemble the specimen of Maruyama et al. (2010) (e.g., https://www.inaturalist.org/observations/108244258), but none of the “true” distinguenda.

Hence, I propose the following approach for iNaturalist: Leptogenys sp. 1 will be added to the undescribed ant observation field, and used for observations that match the specimen in Maruyama et al. (2010). On the other hand, Leptogenys distinguenda (which is currently a subspecies of processionalis but should be a valid species) will be used for the observations that match Emery’s description and the antweb syntype.

References

Brückner, A., Klompen, H., Bruce, A. I., Hashim, R., & Von Beeren, C. (2017). Infection of army ant pupae by two new parasitoid mites (Mesostigmata: Uropodina). PeerJ, 5, e3870.

Emery, C. (1887). Catalogo delle formiche esistenti nelle collezioni del Museo Civico di Genova. Parte terza. Formiche della regione Indo-Malese e dell'Australia (continuazione e fine). Annali del Museo Civico di Storia Naturale 25: 427-432.

Maruyama, M., Von Beeren, C., & Hashim, R. (2010). Aleocharine rove beetles (Coleoptera, Staphylinidae) associated with Leptogenys Roger, 1861 (Hymenoptera, Formicidae) I. Review of three genera associated with L. distinguenda (Emery, 1887) and L. mutabilis (Smith, 1861). ZooKeys, 59(59), 47–60.

Maschwitz, U., Steghaus-Kovac, S., Gaube, R., & Hänel, H. (1989). A South East Asian ponerine ant of the genus Leptogenys (Hym., Form.) with army ant life habits. Behavioral Ecology and Sociobiology, 24(5), 305–316.

Maschwitz, U., & Steghaus-Kovac, S. (1991). Individualismus versus Kooperation. Die Naturwissenschaften, 78(3), 103–113.

von Beeren, C., Maruyama, M., Hashim, R., & Witte, V. (2010). Differential host defense against multiple parasites in ants. Evolutionary Ecology, 25(2), 259–276.

Witte, V., & Maschwitz, U. (2000). Raiding and emigration dynamics in the ponerine army ant Leptogenys distinguenda (Hymenoptera, Formicidae). Insectes Sociaux, 47(1), 76–83.

Witte, V., & Maschwitz, U. (2002). Coordination of Raiding and Emigration in the Ponerine Army Ant Leptogenys distinguenda (Hymenoptera: Formicidae: Ponerinae): A Signal Analysis. Journal of Insect Behavior, 15(2), 195–217.

Witte, V., Leingärtner, A., Sabaß, L., Hashim, R., & Foitzik, S. (2008). Symbiont microcosm in an ant society and the diversity of interspecific interactions. Animal Behaviour, 76(5), 1477–1486.

Witte, V., Foitzik, S., Hashim, R., Maschwitz, U., & Schulz, S. (2009). Fine Tuning of Social Integration by Two Myrmecophiles of the Ponerine Army Ant, Leptogenys distinguenda. Journal of Chemical Ecology, 35(3), 355–367.

Update 11 December 2025: added some new data and clearer figures.

Update 7 May 2026: after measuring about the same number of additional specimens, it has become clear that my measurements have become more accurate over time, probably due to a combination of having more experience with the character definitions and an upgrade in lighting. I will leave this post up for anyone interested, but please note that my current LDA placements correspond better to the background data than the ones shown here.

This post will serve as a more extended summary on the methodology of my morphometrics in the genus Tapinoma. I will focus here on the supercolonial species of the T. nigerrimum group, since they make up most of my material and I was also the most interested in their identification, which is only possible by morphometry or genetic analyses. Identification of most other European Tapinoma, such as those in the erraticum group, is significantly easier and I have so far always had very clear and plausible results with it.

Since this was my first time using such extended character combinations for morphometry, I thought it appropriate to measure a number of control samples to determine how well they match the data of Seifert et al. (2024). Luckily, I was able to collect control samples of previously identified supercolonies of T. magnum (Oostende) and T. ibericum (Rotterdam, Terbregselaan), as well as several ‘semi-control’ samples from Catalonia (l’Estartit) and Campania (Naples) where T. darioi and T. magnum respectively are the only native supercolonial species of the T. nigerrimum group (of course introductions are possible but it's very likely these samples belong to the dominant species of their respective regions). Additionally, I received a single specimen from Algeria, where T. magnum is again the only native species of the group, and 3 nest samples from Croatia, which I also expected to be magnum since it is the only species recorded so far in Eastern Europe (though records are generally sparse in this region; one of these colonies was later also confirmed to be magnum by Seifert).

All the samples mentioned here are uploaded to iNat, with links given below.

Measurements were made using a compound microscope with a reticle in the eyepiece at total magnifications of 100-200x, calibrated with a micrometer slide. Specimens were positioned using a DIY pin-holding stage and illuminated with a light source on a flexible arm. I recorded the full set of 15 characters on all specimens. For data analysis I used the RAV-correction formulas given in Seifert et al. (2024) and ran my samples as wildcards in LDAs using the supplementary data from the study as reference. I also plotted each RAV-corrected character separately to check whether my data matched the variation of the expected species, which it always did.

First I always make sure that my samples fall into the right species groups in an LDA with all 15 RAV-corrected characters. Even at the individual level, the separation of the T. nigerrimum group from the other groups is quite clear:

After that I run an LDA with all species of the nigerrimum group:

The separation of nigerrimum/hispanicum from the supercolonial species is also quite clear at the individual level, but here I’ve used nest sample means for a less busy graph. My samples from l’Estartit all came from well-developed trails, indicating supercoloniality, so I was indeed expecting there to be no nigerrimum/hispanicum in there.

Thus, we arrive at the three supercolonial species, the separation of which is significantly more difficult (especially darioi vs. ibericum) and often requires nest samples, as there is significant overlap at the individual level:

My specimens clearly cluster in a way that corresponds to the clusters of their expected species. However, the points seem to be slightly more spread out compared to the background data, probably reflecting a slightly lower accuracy of my measurements. Nevertheless, all nest sample means of the control and semi-control samples are assigned to the correct clusters with p>0.999:

Furthermore, any combination of 3 specimens of the same sample that I’ve measured are assigned to the correct cluster. Hence, I believe I can conclude that I'm able to properly identify these species, as long as I take into consideration the slightly larger spread compared to Seifert's data. To be safe, I will measure extra specimens whenever possible in unclear or unexpected cases (such as this darioi supercolony in Rotterdam).

Observations

Tapinoma magnum
Oostende: https://www.inaturalist.org/observations/233387492 (included in Seifert et al. 2024)
Naples (Vesuvius): https://www.inaturalist.org/observations/314608988
Naples (Herculaneum): https://www.inaturalist.org/observations/314608989
Croatia (Lukovo Šugarje): https://www.inaturalist.org/observations/306011959
Croatia (Pula): https://www.inaturalist.org/observations/296793714
Croatia (Zagreb): https://www.inaturalist.org/observations/267914953 (later independently confirmed by Seifert)
Tapinoma ibericum
Rotterdam (Terbregselaan): https://www.inaturalist.org/observations/314412293 (included in Seifert et al. 2024)
Tapinoma darioi
l’Estartit 2025-06-15 A: https://www.inaturalist.org/observations/314608979
l’Estartit 2025-06-15 B: https://www.inaturalist.org/observations/314608984
l’Estartit 2025-06-16: https://www.inaturalist.org/observations/314608985
l’Estartit 2025-06-19: https://www.inaturalist.org/observations/314608986
Rotterdam (Raaigras): https://www.inaturalist.org/observations/314608990

References

Seifert, B.; Kaufmann, B.; Fraysse, L. 2024. A taxonomic revision of the Palaearctic species of the ant genus Tapinoma Mayr 1861 (Hymenoptera: Formicidae). Zootaxa 5435 (1):1-74.

Seifert, B.; D'Eustacchio, D.; Kaufmann, B. E.; Centorame, M.; Lorite, P.; Modica, V. M. 2017. Four species within the supercolonial ants of the Tapinoma nigerrimum complex revealed by integrative taxonomy (Hymenoptera: Formicidae). Myrmecological News 24:123-144.