Linepithema humile (Mayr, 1868)

Ivanov, Kaloyan, 2016, Exotic ants (Hymenoptera, Formicidae) of Ohio, Journal of Hymenoptera Research 51, pp. 203-226 : 206

Linepithema humile (Mayr, 1868)

Distribution in Ohio.

Northern Ohio. Counties: Cuyahoga (Cleveland, 27.x.2005 [KI 1176], 15.xi.2005 [KI 1177], and 01.iii.2015 [observed, not coll.], same locality, leg. K. Ivanov, in a greenhouse) and an unspecified Ohio record in Arnett (1993), (Fig. 1 ).

Where found/Habitat.

Indoors, in greenhouses and conservatories.

Origin.

The Paraná River drainage basin of South America.

Natural history.

The Argentine ant is amongst the world’s most successful invasive species and is a nuisance everywhere it occurs. It is established primarily in regions with Mediterranean climate where it has been shown to have profound negative impacts on native biota ( Suarez et al. 1998; Touyama et al. 2003). Workers of this genus can be identified by their broadly concave clypeus and the peculiar mandibular dentition arranged in a series of small denticles interspersed with larger single teeth. In the Northeast Linepithema humile can be separated from the superficially similar Tapinoma by the presence of a well-developed petiolar scale and the vertical orientation of the first gastral segment which does not project over the petiole.

This cosmopolitan species often thrives in disturbed habitats with abundant moisture. Nests are most often in soil, but also under cover objects, refuse piles and more rarely under tree bark. The main dietary component is honeydew from hemipterans, although these ants will also take other sweet substances including household food items, and occasionally will feed on insects ( Smith 1965).

Throughout its introduced range Argentine ant colonies are polygynous with pronounced unicoloniality (i.e., the formation of large colonies with multiple nests). A key attribute to the ecological success of this species thus is the absence of intraspecific aggression within the large colony ( Tsutsui and Case 2001). These characteristics give argentine ant colonies remarkable capacity to expand, and populations can reach extremely large sizes and cover extensive geographic areas to the detriment of other, less populous, species ( Giraud et al. 2002).

Ohio’s only confirmed record of this species comes from a greenhouse in Cleveland where I have observed large numbers of ground foragers on paved surfaces, exposed soil, and on tropical plant debris on the ground. In many cases foragers were accumulating around sugar syrup stations, banana, apple and other fruit pieces used for feeding tropical butterflies. Due to logistical limitations, I was not able to conduct nest searches at this location. The very high worker densities observed, however, suggest that this species now has well-established indoor colonies at this site. At present, this species can survive in the north only in heated buildings, where occasionally it can be a persistent and troublesome pest.

Figures

Figure 1. Distribution of Linepithema humile (1), Tapinoma melanocephalum (2), Nylanderia flavipes (3), and Paratrechina longicornis (4) in Ohio.