Key to males of the Linepithema fuscum group

This key to identify the males of known species of the Linepithema fuscum group is based on Cantone & Di Giulio (2023).

The form of the volsella in the species of Linepithema fuscum group is the main morphological feature used by Wild (2007) to differentiate the species. The digitus was divided by Wild (2007) into proximal arm and distal arm (Fig. 7D). We follow this criterion, which gives the possibility to compare species of the fuscum group (Fig. 7).

1

 * Forewings with one submarginal cell; petiole with ventral process well developed (Fig. 5A, B); pygostyle short (Fig. 5C); proctiger slightly developed (Fig. 5E, F); telomere short and lobiform (Fig. 5C, D); lateral cuspis developed (Fig. 5E, F); ventral basivolsellar process developed (Fig. 5E, F) Linepithema species not in the fuscum group


 * Forewings with two submarginal cells (Fig. 1E); petiole with ventral process slightly developed consisting of a slight convexity (Figs 1D, 3D); pygostyle very long (Fig. 4A); proctiger well developed (Fig. 1G, I); telomere very long and narrow (Fig. 4C); lateral cuspis very reduced (Fig. 4E); ventral basivolsellar process reduced (Fig. 4D) (Linepithema fuscum group)

2

 * Digitus very long, downturned, falcate (Fig. 7A, B, D, E)
 * Digitus moderately long, not downturned, not falcate (Fig. 7C, F)

3

 * Basivolsellar process not pointed apically (Fig. 7B) Linepithema angulatum
 * Basivolsellar process pointed apically (Fig. 7A, D, E)

4

 * Digitus downturned with almost a 90° angle (Fig. 7E); ocular index OI = 37–42; Hispaniola island Linepithema keiteli
 * Digitus downturned with 45° angle (Fig. 7A, D); ocular index OI = 47–52

5

 * Volsellar tooth present distally between basivolsellar process and digitus (Fig. 7A); São Paulo, Brazil Linepithema paulistana
 * Volsellar tooth absent (Fig. 7D); Peru and Ecuador Linepithema fuscum

6

 * Digitus strongly concave dorsally (Fig. 7F) Linepithema tsachila
 * Digitus straight to slightly concave (Fig. 7C) Linepithema piliferum