Melophorus bagoti

This species has been the focus of a number of studies that look at orientation in desert ants, but its thermophilic aspects and nest structure have also gained attention. Along with Melophorus perthensis, this is the best known and most thoroughly researched Melophorus.

Identification
Heterick et al. (2017) - Melophorus bagoti is a member of the Melophoprus aeneovirens species-group (in full-face view, the anterior clypeal margin convex, apron-like and covering whole or part of the retracted mandible, except in Melophorus nemophilus, the medial clypeal sector often produced so that it is protrusive when seen in profile; the psammophore frequently with coarse and well-separated ammochaetae, these always placed on or just above anterior margin; in profile, the propodeum elongate and oblique or broadly rounded). The ant is also placed as a member of the Melophoprus bagoti complex because of the acuminate appearance of the midpoint of the anterior clypeal margin. In full-face view, the psammophore occurs as a row of long, thick setae set slightly above the anterior clypeal margin. Melophorus bagoti has five rows of preapical tibial spines on the metatibia, and this distinguishes it from its sister, Melophorus gracilipes, and all other Melophorus.

Melophorus bagoti is the Melophorus with which the average layperson from the drier rural areas is probably best acquainted because of its bright colour and its size. The size alone makes this species unmistakable except for M. gracilipes, from which it can be distinguished by the presence of five rows of tibial spurs (compared with the normal two rows in the latter species).

Distribution
Melophorus bagoti has been recorded from all mainland Australian states except Victoria, but appears to be most common in the NT and WA.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Biology
Heterick et al. (2017) - In drier regions M. bagoti workers are frequently seen scurrying rapidly over the ground surface foraging for seeds and carrion. In the Kimberley, the principal author also saw many workers climbing over a small shrub when it was in flower, seeking nectar.

Navigation
Lionetti and Cheng (2019) - The red honey ant Melophorus bagoti is a thermophilic desert ant that forages in the heat of day during the southern summer months (Cheng, Narendra, Sommer, & Wehner, 2009; Christian & Morton, 1992; Muser, Sommer, Wolf, & Wehner, 2005; Schultheiss & Nooten, 2013). The species forages individually for arthropod remains and plant materials. Melophorus bagoti use path integration for returning to the nest from foraging. Workers keep track of the distance and direction travelled from the nest and use the updated vector for homing. They are also known to adjust their vectors derived from path integration to compensate for mismatches between their outbound direction of travel and (the reverse of) the inbound direction of travel that takes them home, a process known as vector calibration. These desert ants have occasionally been observed to be blown a small number of metres by wind, generating a situation of directional conflict (K.C., personal observations). The disagreement between the inbound vector and outbound vector information causes foragers to alter their subsequent inbound and outbound route directions towards the vector memory of previous trips’ inbound route information. In the current study, we test how a temporal variable, time since an experience, affects vector calibration in M. bagoti. Imposing a delay between the outbound and inbound journeys did not speed up or improve calibration, either in an experimental test ring or at the displacement site. Calibration proceeded similarly no matter what the delay between the outbound and inbound vectors.

Morphology
Penmetcha et al. (2019) - Desert ants of the genus Cataglyphis and Melophorus possess all three ocelli and are the only ants in which the function of the ocelli has been studied. Size of the ocellar lens and width of the ocellar rhabdoms in cross-section are typically larger in nocturnal insects (Warrant et al. 2006; Somanathan et al. 2009; Narendra et al. 2011; Narendra and Ribi 2017). This increases their optical sensitivity and allows individuals with larger ocelli to forage in slightly dim light conditions (Wellington 1974). The desert ants that we studied being strictly day-active had small lenses and narrow rhabdoms (in Cataglyphis spp) compared to the night-active Myrmecia. Here we characterised the anatomical organisation of the ocelli in three species of desert ants (Cataglyphis bicolor, Cataglyphis fortis, and Melophorus bagoti). The central Australian desert ant, M. bagoti, possesses unusual rhabdoms that form a pentagonal or a hexagonal network. This forms an open rhabdom. This is unlike in any other ant or hymenopteran ocelli that has been studied to date. The ocellar retinae of M. bagoti resembles the ocellar retinae of the bibionid flies, Dilophus febrilis, (Wunderer et al. 1988), flesh flies, Boettcherisca peregrine, (Toh et al. 1971) and the hoverfly, Eristalis tenax (Ribi and Zeil 2018). In these four species, each retinula cell contributes microvilli in more than one orientation making their ocelli unsuitable for measuring changes in the pattern of polarised light. Behavioural investigation of function of ocelli in M. bagoti has shown that they can derive celestial compass information, though the specific nature of these cues is unknown (Schwarz et al. 2011a). One possibility is that M. bagoti use the ocelli to obtain compass information by relying on the sun or spectral cues (Rossel and Wehner 1984). At present the ocellar spectral sensitivity in M. bagoti is unknown. However, insects that operate in cluttered landscapes appear to have UV and green receptors.

Nomenclature

 *  bagoti. Melophorus bagoti Lubbock, 1883: 52, pl. 2, figs. 1-10 (w.) AUSTRALIA.
 * Forel, 1886f: 213 (s.); Forel, 1910b: 60 (q.); Wheeler, G.C. & Wheeler, J. 1953c: 129 (l.).
 * Status as species: Forel, 1886f: 213; Dalla Torre, 1893: 175; Forel, 1910b: 60; Forel, 1915b: 87; Emery, 1925b: 12; Taylor & Brown, 1985: 122; Bolton, 1995b: 250; Heterick, et al. 2017: 134 (redescription).
 * Senior synonym of cowlei: Clark, 1930c: 22; Heterick, et al. 2017: 134.
 * cowlei. Camponotus cowlei Froggatt, 1896: 387, pl. 27, figs. 1-5 (w.q.m.) AUSTRALIA.
 * Combination in C. (Myrmophyma): Emery, 1925b: 110.
 * Combination in Camponotus: Taylor & Brown, 1985: 112.
 * Combination in Melophorus: Wheeler, W.M. 1908d: 388; Clark, 1930c: 22; Heterick, et al. 2017: 134.
 * Status as species: Emery, 1898a: 226; Emery, 1925b: 110; Taylor & Brown, 1985: 112; Bolton, 1995b: 94; McArthur, 2007a: 335; Heterick, 2009: 69; McArthur, 2010: 78; McArthur, 2014: 54.
 * Junior synonym of bagoti: Clark, 1930c: 22; Heterick, et al. 2017: 134.

Worker
Heterick et al. (2017) - (n = 8): CI 99–118; EI 16–22; EL 0.30–0.52; HL 1.41–2.81; HW 1.39–3.33; ML 2.66–4.59; MTL 1.91–3.01; PpH 0.32–0.47; PpL 1.23–1.73; SI 81–147; SL 2.04–2.71.

Minor. Head. Head square or rectangular, tending to trapezoid; posterior margin of head extended posteriad as a convex, sloping surface with a slight medioccipital protuberance; frons shining with superficial shagreenation or microreticulation only; frons consisting exclusively or almost exclusively of well-spaced, appressed setae only (small, erect setae, if present, usually confined to ocular triangle or posterior margin of head). Eye moderate (eye length 0.20–0.49 length of side of head capsule); in full-face view, eyes set above midpoint of head capsule; in profile, eye set anteriad of midline of head capsule; eyes elliptical or slightly reniform. In full-face view, frontal carinae straight or weakly convex; frontal lobes straight in front of antennal insertion. Anteromedial clypeal margin convex, weakly acuminate anteromedially; clypeal psammophore set at or just above anterior clypeal margin; palp formula 6,4. Five to six mandibular teeth in minor worker; mandibles triangular, weakly incurved; third mandibular tooth distinctly shorter than apical tooth and teeth numbers two and four; masticatory margin of mandibles approximately vertical or weakly oblique. Mesosoma. Integument of pronotum, mesonotum and mesopleuron uniformly shagreenate to moderately shining and shagreenate throughout; anterior mesosoma in profile broadly convex; erect pronotal setae absent; in profile, metanotal groove shallow, broadly V or U-shaped; propodeum shining and shagreenate; propodeum smoothly rounded or with indistinct angle or bluntly angulate; length ratio of propodeal dorsum to its declivity about 2:1; propodeal dorsum and declivity confluent; erect propodeal setae always absent; appressed propodeal setulae short, separated by more than own length and inconspicuous; propodeal spiracle situated at least twice its width from the declivitous face of propodeum, and shorter (length < 0.50 × height of propodeum). Petiole. In profile, petiolar node a broadly right-angled triangle, node with steeply declivitous posterior face; in full-face view, shape of petiolar node uniformly rounded; node shining and smooth throughout. Gaster. Gaster smooth and glossy or shining, shagreenate (‘LP record’ appearance); pilosity of first gastral tergite consisting of well-spaced short, inconspicuous, appressed setae, erect setae (present in at least some workers) confined to margin of sclerite. General characters. Colour mostly uniformly deep orange, but some workers with foreparts and appendages orange, and gaster black with blue-green iridescence.

Major. Head. Head horizontally rectangular, broader than wide; posterior margin of head planar or weakly convex; cuticle of frons ranging from matt or with weak sheen, indistinctly shagreenate through to shining with superficial shagreenation or microreticulation; pilosity of frons a mixture of a few well-spaced, erect setae interspersed with appressed setae only. Eye moderate (eye length 0.20–0.49 length of head capsule); in full-face view, eyes set above midpoint of head capsule; in profile, eye set anteriad of midline of head capsule; eyes elliptical. In full-face view, frontal carinae straight or weakly convex; frontal lobes straight in front of antennal insertion. Anterior clypeal margin convex, acuminate anteromedially, margin entire; clypeal psammophore set at or just above anterior clypeal margin; palp formula 6,4. Five to six mandibular teeth in major worker; mandibles triangular, weakly incurved; third mandibular tooth distinctly shorter than apical tooth and teeth numbers two and four; masticatory margin of mandibles approximately aligned vertically or weakly oblique. Mesosoma. Integument of pronotum, mesonotum and mesopleuron moderately shining and shagreenate throughout; anterior mesosoma in profile broadly convex; erect pronotal setae long (i.e., longer than length of eye) and unmodified; in profile, metanotal groove shallow, broadly V- or U-shaped; propodeum shining and shagreenate, or matt or with a weak sheen and microreticulate; propodeum angulate, propodeal angle blunt; length ratio of propodeal dorsum to its declivity between 3:2 and 4:3; erect propodeal setae absent; appressed propodeal setae short, separated by more than own length and inconspicuous; propodeal spiracle situated at least twice its width from the declivitous face of propodeum, and shorter (length less than 0.50 × height of propodeum). Petiole. In profile, petiolar node a broadly right angled triangle, node with steeply declivitous posterior face; in full-face view, shape of petiolar node generally rounded with median indentation; node shining and faintly shagreenatemicroreticulate. Gaster. Gaster shining, shagreenate (‘LP record’ appearance); pilosity of first gastral tergite consisting of well-spaced short, inconspicuous, appressed setae, erect setae (present in at least some workers) confined to margin of the sclerite. General characters. Colour as for minor worker.