Monomorium exiguum Forel 1894

Monomorium exiguum Forel, 1894 Materials Type status: Other material. Occurrence: individualCount: 1 worker; occurrenceID: 536F5F1A-9029-58A4-A5F4-FF17AF2C0BE5; Taxon: genus: Monomorium; specificEpithet: exiguum; scientificNameAuthorship: Forel 1894; Location: island: La Réunion; country: France; municipality: Petite Île; verbatimElevation: 378 m; decimalLatitude: - 21.34378; decimalLongitude: 55.54950; Identification: identifiedBy: D. Carval; Event: samplingProtocol: interception trap; verbatimEventDate: 19. XII. 2023; habitat: sugarcane field; Record Level: collectionID: CDC Diagnosis Amongst the 20 Monomorium species reported in the Malagasy Region (Fisher and Bolton 2016), M. exiguum is easily distinguished by its 11 - segmented antennae (M. monomorium species group), a metanotal groove weakly impressed, an elongated propodeum and a petiolar node that is conical and dorsally tapered (Heterick 2006) (Fig. 8). All other Monomorium species reported from La Réunion Island have 12 - segmented antennae (Monomorium floricola (Jerdon, 1851), Monomorium pharaonis (Linnaeus, 1758), Monomorium subopacum (Smith, 1858) and Monomorium termitobium (Forel, 1892)). This species displays great variability in colour, from yellow pale to brown (Heterick 2006), but our specimen was a pale orange similar to that found in M. exiguum flavescens (Forel, 1916), now considered as a junior synonym of M. exiguum (Bolton 2014). Distribution This species is native to the Afrotropical Region, where it is widely distributed in sub-Saharan Africa, including Madagascar (AntWeb 2024) and the Arabian Peninsula (Aldawood and Sharaf 2009). It has been reported as introduced on the Socotra Archipelago (Sharaf et al. 2018), in the Balearic Islands (Gómez and Espadaler 2006) and in Crete (Borowiec et al. 2023). This is the first report of this species in the Mascarene Islands. Ecology Monomorium exiguum appears adapted to numerous types of habitats. In the Arabian Peninsula, it has been found in humid soil, in leaf litter, under rocks and under the bark of trees (Sharaf et al. 2018). Interestingly, it has been found inside the galleries of a Camponotus species (Sharaf et al. 2018) and inside the galleries of a termite nest (Sharaf et al. 2017). In the Province of Tolaria in Madagascar, M. exiguum has been found to be the most abundant Monomorium species in leaf litter samples (Heterick 2006). In Benin, one specimen was found in a mango orchard with no specification of the microhabitat (Taylor et al. 2018). In La Réunion Island, the specimen was found in a sugarcane field.