Acromyrmex lobicornis

An inhabitant of desert areas, this fungus growing ant harvests vegetation from a large range of plants. Acromyrmex lobicorni form large colonies, ~10,000 workers in a mature colony, and forage in well defined columns.

Distribution based on Regional Taxon Lists
Neotropical Region: Argentina, Bolivia, Brazil, Paraguay, Uruguay.

Biology
Jofre et al. (2018) - Acromyrmex lobicornis is one of the most common leaf-cutting ant species in Argentina (Farji-Brener & Ruggiero, 1994). This species constructs nests with an external nest-mound (Farji-Brener, 2000; Bollazzi et al., 2008) that house about 10.000 workers (Jofré & Medina, 2012) and build well defined trails to forage. Acromyrmex lobicornis consumes a high percentage of species available in the environment (Armani & Quirán, 2007; Nobua-Behrmann, 2014), and their degree of selectivity or opportunism depends on the availability of resources within the proximity of their colonies (Farji-Brener & Protomastro, 1992; Pilati et al., 1997; Franzel & Farji-Brener, 2000; Armani & Quirán, 2007; Nobua-Behrmann, 2014).

Foraging
Nobua-Behrmann et al. (2017) studied temporal and thermal aspects of Acromyrmex lobicornis foraging behavior in the Monte Desert in Argentina where this species co-occurs with Acromyrmex striatus. Acromyrmex lobicornis colonies actively foraged from spring to autumn, with occasional external activity during winter. Foraging intensity was highest during spring and summer, with up to 150 ants (foragers returning to the nest) / 5 minutes. During spring and summer, A. lobicornis foraged mostly during the night, starting at dusk and continuing for up to 16 hours until the next morning. Colonies switched to diurnal foraging in autumn, when temperatures are lower. During the hottest months, the overall daily foraging pattern appears to be complementary to its similar co-occurring congener: A. striatus daily foraging activity begins in the mornings when A. lobicornis colonies are ceasing their foraging activity cycle. Furthermore, the ending of A. striatus colonies foraging activity in the evenings also coincides with the beginning of A. lobicornis foraging. During autumn, colonies still showed considerably high foraging activity (up to 80 ants / 5 minutes). Daily and seasonal variations in nest maintenance activity were broadly similar to foraging activity patterns, though spanning larger time ranges than their foraging activity (starting earlier and finishing later).

The ants foraged within a particular temperature range that was relatively constant throughout the year and differed from its congener: A. striatus colonies foraged at higher temperatures than A. lobicornis in all seasons (26 - 45 °C vs. 16 - 35 °C, respectively).

Jofre et al. (2018) - Foraging behavior was studied in a natural reserve of San Luis, Argentina. The chaco vegetation found within the reserve had in the past been affected by overgrazing, fire, and logging. In addition to quantifying the plants selected by foragers, it was found that small and large nests showed similar feeding behavior.

Nomenclature

 *  lobicornis. Atta (Acromyrmex) lobicornis Emery, 1888c: 358 (w.) BRAZIL. Emery, 1905c: 52 (q.m.). Combination in Acromyrmex: Bruch, 1914: 216. [Incorrectly recorded from Ivory Coast: Santschi, 1928f: 209.] Senior synonym of bucki, rufidens: Gonçalves, 1961: 148. Current subspecies: nominal plus cochlearis, ferrugineus, pencosensis, pruinosior.
 * bucki. Acromyrmex bucki Wasmann, 1931: 106 (w.) BRAZIL. Junior synonym of lobicornis: Gonçalves, 1961: 148.
 * rufidens. Acromyrmex lobicornis var. rufidens Santschi, 1933e: 120 (w.) BRAZIL. Junior synonym of lobicornis: Gonçalves, 1961: 148.