Odontomachus haematodus ( Linnaeus, 1758 )

Macgown, Joe A., Boudinot, Brendon, Deyrup, Mark & Sorger, D. Magdalena, 2014, A review of the Nearctic Odontomachus (Hymenoptera: Formicidae: Ponerinae) with a treatment of the males, Zootaxa 3802 (4), pp. 515-552 : 536-540

Odontomachus haematodus ( Linnaeus, 1758)

( Figs. 3 , 11 , 18 , 19 , 24 , 25 , 26 )

Formica haematoda Linnaeus, 1758: 582 (queen) “ America Meridionali; Emery, 1899: 5 (larva); Wheeler & Wheeler, 1952: 646 (larva). Combination in Odontomachus: Latreille, 1804: 179 .

Formica maxillosa DeGeer, 1773: 601 . Junior synonym of O. haematodus: Retzius, 1783: 75 ; Olivier, 1792: 502; Latreille, 1802: 192.

Odontomachus hirsutiusculus Smith, F., 1858: 78 . Junior synonym of O. haematodus: Roger, 1861: 24 ; Brown, 1976: 104. Odontomachus haematoda var. pallipes Crawley, 1916: 368 . Junior synonym of O. haematodus: Brown, 1976: 104 . Odontomachus haematodus r. pubescens var. beuneipes Emery, 1893: 91 . Unavailable name; material referred to O.

haematodus: Brown, 1976: 104 .

Diagnosis. Workers in the Nearctic region are identified by their unique large size, dark color, lightly shagreened gastral dorsum, and presence of elongate metasternal processes between the hind coxae ( Fig. 3 ), a character unique for the Nearctic fauna. The yellow colored males are most similar to O. brunneus , but can be separated by the following: 1) ocelli small, weakly bulging past posterior head margin; 2) posterior propodeal face offset dorsally and laterally by distinct carina; 3) metasternal processes long and narrow; and by numerous genitalic characters. Genitalia of O. haematodus are unique among Nearctic species, with the telomere distinctly taller than long. The ninth abdominal sternum is most similar to that of O. ruginodis , having similarly proportioned discs and strongly constricted posterior lobes, but O. haematodus has a broader posterior lobe apex.

Description. Worker: HL 2.32–2.75, HW 1.88–2.16, SL 2.16–2.48, EL 0.44–0.54, ML 1.38–1.56, WL 3.04–3.48, PTH 1.22–1.38, PTL 0.54–0.60 (n=10). Entire body generally shiny except where dulled by dense pubescence; concolorous dark reddish-brown to blackish. Head with fine, longitudinal striae covering much of the head in full-face view, striae beginning from frontal lobes and diverging toward posterior corners of head, fading at corners and sides; sides and underside of head lacking sculpture; with numerous, fine, appressed pubescence and scattered elongate, erect setae present (dorsally). Pronotum with somewhat circular concentric striae that become longitudinal near rear margin; appressed pubescence abundant; 5-8 elongate, erect setae present. Mesonotum and propodeum with deep transverse striae; propleuron, mesopleuron, and basalar lobe lacking sculpture; abundant pubescence present dorsally. Metasternum with paired narrowed, elongate, spiniform processes between hind coxae ( Fig. 3 A). Petiole widest at base, gradually tapering apically to a long spine directed rearward; transverse striae completely surrounding petiole except upper dorso-posteriorly where striae are faint or lacking; subpetiolar process somewhat anvil shaped; appressed pubescence present anteriorly and laterally, but mostly absent posteriorly. Gaster mostly shiny beneath pubescence, lacking striae or other strong sculpture, but weakly shagreened (seen at high magnification); fine, appressed pubescence moderately dense, spaces between hairs usually less than 1/2 the length of a hair; scattered erect, elongate setae present.

Male: HL 1.00–1.12, HW 1.20–1.30, SL 0.18–0.20, EL 0.62–0.68, EW 0.36–0.40, OL 0.18–0.20, OES 0.20–0.22, WL 2.68–2.83, PTH 0.90–0.94, PTL 0.50–0.56, FWL 4.70–5.45 (n=5). Body generally shiny except where obscured by dense pubescence; head, meso- and metasoma yellowish-orange, antenna and legs pale yellowish-orange. Head and body with abundant fine, white pubescence except on anepisternum, where it is mostly absent. Eyes extremely large, maximum diameter of each eye at least 70% of the length of the head in full-face view. Ocelli small to average in size, the length of each ocellus slightly less to approximately the same as the distance between lateral ocellus and eye margin; in full-face view, lateral ocelli do not protrude beyond posterior border of head. Mesosoma: pronotum with faint transverse striae, especially laterally, but mostly appearing to lack sculpture; mesoscutum with faint transversely arcuate striae anteriorly, striae becoming transverse posteriorly; mesoscutellum raised and convex, lacking sculpture; propodeum evenly rounded without obvious declivious face, with strong rugoreticulation; mesopleuron mostly lacking striae or with very faint longitudinal striae. Petiole bluntly rounded apically, with rounded triangular subpetiolar process anteriorly; densely pubescent anteriorly and laterally, but reduced pubescence posteriorly. Abdominal sternum IX disc subrectangular, breadth about twice length; posterior lobe length about twice maximum lobe width, basal half strongly narrowed. Telomeral apex very narrowly rounded, nearly angular; telomere length distinctly shorter than height; valviceps apex weakly produced, broad; apical margin of valviceps linear; vertical portion of dorsolateral carina and lateral margin of subapical lamina meeting at an angle; apicodorsal lobe of valviceps narrow, somewhat short; subapical lamina broad.

Queen: HL 2.48–2.55, HW 2.14–2.00, SL 2.35–2.36, EL 0.52–0.55, ML 1.56–1.58, OL 0.12–0.13, WL 3.56- 3.60, PTH 1.28–1.62, PTL 0.58–0.66, FWL 6.5 (n=2 except for FWL for which only one individual had wings). Similar to workers in color and general appearance except with mesosoma developed for wings and with wings present in alate specimens.

Distribution ( Fig. 26 , Appendix 1): Due to misidentifications, the worldwide distribution of this species is not clearly understood at this time. However, based on recent examination of numerous specimens from the US, the distributional records for this species from this country given here (Appendix 1) can be considered reliable. Additionally, specimens from Brazil, British Guiana, and Peru were identified as O. haematodus by MacGown [LSAM, UGCA, and UMMZ]. Brown (1976) reported this species' distribution as continental South America from Orinoco Delta to Tucuma, Argentina. McGlynn (1999) reported O. haematodus as being introduced to Hawaii; however, these records have not been verified, nor is this species thought to have been established in that state. Krushelnycky et al. (2005) did not include O. haematodus in their recent list of ant species from Hawaii. In the US we have verified records of established populations of this species only from the Gulf Coast region, specifically from: Alabama: Baldwin, Escambia, and Mobile Counties. Florida: Escambia County. Louisiana: Orleans Parish. Mississippi: Greene and Jackson Counties. Distributional information for US specimens from AntWeb (2013) (Florida record), and examination of specimens in AUEM, MEM and USNM.

Discussion. Odontomachus haematodus is native to South America. The earliest record in the US we found was of three specimens collected on 1 June 1956 from Mobile, Alabama. These specimens were borrowed from the USNM and examined by MacGown. Earliest MEM records are from 2000 from Baldwin County, Alabama, by which time this species had become locally abundant. Until recently, specimens of this species from the Gulf Coast were identified as O. insularis , O. brunneus , and/or O. ruginodis . However, after examination of workers and males of all three species, it became clear that this now-common Gulf Coast species is O. haematodus .

This species has been collected in a variety of habitats along the Gulf Coast including bottomland forests, pine forests, in a mixed forest at the edge of estuary, at the edge of a pitcher plant bog, fore dunes, shell midden, pine savanna, sandhill, and in residential areas. In non-urban areas, nests have been discovered in the soil, in leaf litter, in rotting logs and stumps, at tree bases, in dead parts of standing live trees (colonies observed in tree cavities at least 2.0 m from ground level); in urban areas nests have been discovered under mulch, debris, under roots of ornamental grass bushes, in building foundations, and under PVC pipes. Colonies range in size from less than a hundred workers to several thousand with some colonies polygynous. Similar to other members of the genus, workers are typically nocturnal, but may also forage during the day. In areas in the Gulf Coast where this species occurs, populations may be extremely abundant, especially in parts of Baldwin and Mobile Counties, Alabama; and Jackson County, Mississippi. Large populations have also been observed at the Audubon Zoo in New Orleans, Louisiana ( Pers. Comm. Fred Larabee and Andy Saurez). Compared to other US species, O. haematodus is an aggressive stinger. Upon placing one's hand in leaf litter where a nest is located, workers may immediately sting. The sting is painful, but not long lasting (MacGown, personal observation). Homeowner's in southern Mississippi have complained of bites and stings received from this species (MacGown, unpublished data). One homeowner stated, "[the] ants would latch on with their mandibles and sting repeatedly, lashing out with their abdomens. One ant can sting 4–5 times before you realize it. They are very aggressive." Alate males and queens have been collected from late June through early August.

It is clear from collecting records that the abundance of O. haematodus along the Gulf Coast is a recent phenomenon, and it is also clear that this species is continuing to spread. This suggests that O. haematodus spent around 50 years in North America before some threshold condition allowed it to form such large populations that they became conspicuous. This kind of history would not be unique to O. haematodus . Camponotus planatus , for example was restricted to a small area of tropical Florida for many decades, arriving some time before 1910 ( Deyrup et al. 2000). This species is now common in some sites (including some natural habitats) in central peninsular Florida (Deyrup 2014, unpublished data) and has even been recorded in Mississippi ( MacGown 2010). It is always possible, however, that the 1956 collection of O. haematodus represents an independent failed introduction.

Figures

FIGURE 3. Worker metasterna, anteroventral oblique view: (A) O. haematodus with both hindcoxae removed, arrow indicating elongate metasternal processes and (B) O. ruginodis with one hindcoxa removed, arrow indicating cleft ridge.

FIGURE 11. Male metasterna, anteroventral oblique view, with arrow indicating sternal processes: (A) O. ruginodis and (B) O. haematodus.

FIGURE 18. Odontomachus haematodus, worker: (A) head in full-face view, (B) lateral habitus, (C) dorsal habitus, (D) mesosoma in dorsal view, (E) mesosoma in lateral view, (F) petiole in lateral view, and (G) first gastral tergite in dorsal view showing pubescence.

FIGURE 19. Odontomachus haematodus, male: (A) head in full-face view, (B) lateral habitus, (C) dorsal habitus, (D) body in lateral view, (E) mesosoma in lateral view, (F) body in dorsal view, and (G) mesosoma in dorsal view.

FIGURE 24. Male Odontomachus abdominal sternum IX, mesal view; all scale bars 0.2 mm. (A) Odontomachus brunneus; (B) O. clarus; (C) O. desertorum; (D) O. haematodus; (E) O. relictus; (F) O. ruginodis.

FIGURE 25. Male Odontomachus genitalic sclerites, left-hand side; arrows indicate anterior; all scale bars 0.2 mm. (A – F) Paramere and volsella, medial view; (G – L) penisvalva, lateral view. (A, G) Odontomachus brunneus; (B, H) O. clarus; (C, I) O. desertorum; (D, J) O. haematodus; (E, K) O. relictus; (F, L) O. ruginodis. Abbreviations: ADL = apicodorsal lobe; AP = apicoventral process; AVP = anteroventral process; BM = basimere; CU = cuspis; DI = digitus; DLC = dorsolateral carina; DS = diagonal sclerotization; SAL = subapical lamina; TM = telomere; VC = valviceps; VO = volsella; VU = valvura.

FIGURE 26. Map of the southern United States (by county) and northern Mexico (by state) showing the known occurrences of Odontomachus brunneus (black square), O. clarus (black circle), O. desertorum (magenta square), O. haematodus (yellow square), O. relictus (red triangle), and O. ruginodis (orange and white circle).