Monomorium fieldi

Monomorium fieldi
fig. 1: Monomorium fieldi, worker
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Family:	Formicidae
Subfamily:	Myrmicinae
Tribe:	Solenopsidini
Genus:	Monomorium
Species:	M. fieldi
Binomial name
Monomorium fieldi Forel, 1910

Monomorium fieldi is a small species of ant, originally described from Australia by Forel (1910), where it is widespread in all states (Heterick, 2001). According to Gunawardana (2005), it is also found in New Zealand, based on the following evidence:

• Don has determined that all material from New Zealand previously identified as Monomorium orientale is in fact M. antipodum
• recent material from Onehunga (New Zealand), tentatively determined as M. orientale by Don, was tentatively reidentified as M. fieldi by Heterick
• further recent material from New Zealand, collected by J.W. Early, was determined as M. fieldi by both Heterick and Shattuck
• Shattuck similarly determined all New Zealand material sent to him, including material previously identified as M. antipodum, as M. fieldi

Note that Gunawardana (2005: 15) concludes by stating 'Monomorium antipodum Forel was first described in 1901 from Auckland (Hymenoptera Name server 2001), and with confirmation of the identity of M. fieldi, it is possible that M. fieldi may be the junior synonym of M. antipodum (S. Shattuck, November 2004, personal communication). Clearly, the taxonomy of the New Zealand Monomorium needs to be revisited to clarify the validity of the species name antipodum'. Hence, Gunawardana's argument is that since all (checked) material from New Zealand, previously identified as M. orientale or M. antipodum, has been consistently redetermined now to be M. fieldi, it is possible that M. fieldi is a junior synonym of M. antipodum, but this must await confirmation by examination of more material, including the type material of M. antipodum (if it still exists), in the context of a taxonomic revision of the Monomorium of New Zealand, which has not yet been undertaken. However, Don (2007: 112-113) doubts that the New Zealand material is conspecific with the Australian species (M. fieldi), based on the results of alkaloidal analyses. If Don (2007) is correct, then the species currently being called M. fieldi in New Zealand may in fact be an endemic species, presumably M. antipodum, which is the name used by Don (2007), because he argues that it either is synonymous with M. fieldi or not, and in either case the valid name would be M. antipodum (if synonymous, then M. antipodum would also be the valid name for what is currently being called M. fieldi in Australia). The fallacy in Don's argument is that at present, it can only be speculated that the name M. antipodum applies to the material from New Zealand that has been examined above, but this has not been rigorously established, it being possible that there is more than one species present in New Zealand, with the true M. antipodum not being represented among the recently examined material. Therefore the identity and nomenclature of M. antipodum and M. fieldi is at present still very unclear. It should be noted that brachyptery has not been reported for M. fieldi queens from Australia (Heterick, 2001: 402), but has been reported from New Zealand (Don, 2007: 112), and indeed it is not entirely clear if fully winged queens occur in New Zealand (see fig. 2 for a photo of a brachypterous queen from New Zealand). At present, the safest option is to call the New Zealand material Monomorium cf. fieldi, and consider M. antipodum to be a species inquirenda. Berry in Macfarlane et al. (2010: 455) listed M. fieldi from New Zealand as a species inquirenda, and made no mention of M. antipodum. However, it is the species corresponding to the name M. antipodum which is uncertain, not the species corresponding to M. fieldi. It is at present unclear if material from New Zealand is correctly identified as M. fieldi, but this does not make M. fieldi into a species inquirenda.

fig. 2: Monomorium cf. fieldi, alate (brachypterous) queen, length about 3 mm, from New Zealand

References

• Don, W. 2007: Ants of New Zealand. Otago University Press, New Zealand. ISBN 9781877372476
• Forel, A. 1910: Formicides australiens reçus de MM. Froggatt et Rowland Turner. Revue suisse de zoologie, 18: 1-94. ISSN 0035-418X BHL Internet Archive PDF
• Gunawardana, D. 2005: Monomorium fieldi Forel (Hymenoptera: Formicidae) is the current name to use for ants previously known as Monomorium antipodum Forel and Monomorium orientale Mayr in New Zealand. Weta, 30: 14-15. ISSN 0111-7696 PDF
• Heterick, B.E. 2001: Revision of the Australian ants of the genus Monomorium (Hymenoptera: Formicidae). Invertebrate taxonomy, 15(3): 353-459. ISSN 1445-5226 doi:10.1071/IT00003
• Macfarlane, R.P. et al. 2010: [Chapter] NINE Phylum ARTHROPODA SUBPHYLUM HEXAPODA Protura, springtails, Diplura, and insects. Pp. 233-467 in Gordon, D.P. (ed.): New Zealand inventory of biodiversity. Volume 2. Kingdom Animalia. Chaetognatha, Ecdysozoa, ichnofossils. Canterbury University Press, Christchurch, New Zealand. ISBN 978-1-87725793-3
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