First record of the Argentine ant, Linepithema humile (Mayr, 1868) (Hymenoptera: Formicidae), from the Malagasy region

Figures & data

Figure 1. Map of the island of La Réunion with the 22 sampled fields (black dots). The three fields where the Argentine ant was discovered are illustrated with red dots.

Table 1. Details of the farm localities where individuals of the Argentine ant were sampled.

Farm	Date	Crop species	Trap	Altitude (m)	Area (m²)	Coordinates	L. humile individuals
Farm 5	17.III.2023	Fallow	Cornet	1307	2391	21°12′38.8″S 55°32′33.8″E	23
Farm 5	27.X.2022	Cucurbita pepo	Cornet	1307	1864	21°12′38.1″S 55°32′34.4″E	2
Farm 12	31.III.2023	Lactuca sativa	Cornet	993	768	21°14′26.6″S 55°32′01.3″E	23
Farm 3	13.IX.2022	Brassica oleracea	Pitfall	1143	295	21°13′14.0″S 55°31′45.7″E	148
Farm 3	30.III.2023	Capsicum annuum	Cornet	1143	174	21°13′14.1″S 55°31′45.7″E	19

Figure 3. Linepithema humile worker, individual collected in March 2023 from the municipality of Le Tampon (97430). A, Full-face view; B, lateral view; C, dorsal view.

Table 2. Morphological measurements and indices from 10 worker individuals.

	HL (µm)	HW (µm)	SL (µm)	EL (µm)	CI	SI	NO	NT	ND
Mean	683	584	719	179	86	123	89	7	7
Range	639–709	533–613	698–762	168–192	81–91	114–131	82–100	5–8	5–9
Reference range	620–780	530–720	620–800	–	84–93	108–126	82–102	5–8	5–13

HL = head length, HW = head width, SL = scape length, EL = eye length, CI = cephalic index (HW/HL × 100), SI = scape index (SL/HW × 100), OI = ocular index (EL/HL × 100), NO = number of ommatidia, NT = number of teeth, ND = number of denticles. The reference ranges are from Wild (2007, n = 81) and Gómez & Abril (2008), the latter only for NT and ND.

Figure 2. A, View of Farm 5 where the first Argentine ant individuals were caught in October 2022. B, Large rocks around crop fields are typical nesting shelter sites of Linepithema humile. C, Disturbed ant individuals displacing brood. D, Malva parviflora L. (Malvales: Malvaceae) is a common plant in disturbed areas of La Réunion which hosted ant individuals on this farm. E, Ant individual feeding on floral nectar from M. parviflora.

Wild AL. 2007. Taxonomic revision of the ant genus Linepithema (Hymenoptera: Formicidae). California: Univ of California Press.

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Gómez C, Abril S. 2008. Linepithema humile (Argentine ant). CABI Compendium. CABI Compendium:30839. https://doi.org/10.1079/cabicompendium.30839.

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