Formica bicolor, Fabricius, 1793

Agosti, Donat, 1990, Review and reclassification of Cataglyphis (Hymenoptera, Formicidae), Journal of Natural History 24, pp. 1457-1505 : 1476-1479

bicolor group

Diagnosis

Workers and females: Catagylphis ants with the following diagnostic characters:

1. Petiole nodiform, in lateral view rounded dorsally (Fig. 9). In locomotion with the gaster bent dorsally, forming an acute angle between the ventral surface of the gaster and a line spanned between the anteriormost and posteriormost point of the alitrunk (Fig. 3).

2. MPI> 90; third segment compressed in cross-section, with long erect hairs on the margins and the outer surface.

3. Uniform black to bicoloured, with head and parts or entire alitrunk red and gaster black, surface dull or shining.

4. Head finely reticulate sculptured.

5. Striking monophasic variation in body size of workers; alitrunk length of large workers <5 mm, of small workers <2 mm.

6. Petiole of female nodiform as in workers.

Males: Catagylphis ants with the following diagnostic characters:

1. Uniform black to complete yellow body, whereby the three bands on the dorsum of the alitrunk are only weakly present.

2. Subgenital plate long (SPI> 125); with two distal, lateral, finger-shaped processes and a median part which is also finger-shaped but variable in length (Figs 20-24).

3. Squamula and stipes caudally always confluent (Figs 35-39).

4. Stipes with a large median appendix with a modified topology, its largest diameter is about half the length of the stipes or less (Figs 35-39).

5. Volsella curved, distally truncated or acute (Figs 55-59).

6. Sagitta with a medioapical appendix; the serrated face always developed and a row of teeth present; the median carinae leading to the medioapical appendix (Figs 70-74).

Distribution

The distribution of the bicolor species-group is almost identical with that of the whole genus; it is not present in the Iberian peninsula, the northwestern Mediterranean or southern Italy. It is also absent from the higher altitudes of the mountains (almost always occurring below 1500 m) and in desert habitats. The distribution map given by Wehner et al. (1983) for bicolor includes references to all the bicoloured species of the bicolor species-group, including some doubtful unconfirmed records from the Iberian peninsula, but not those of the niger complex. The ants of the bicolor species-group can be active at temperatures of 45°C but then it is always near trees or shurbs, e.g. on the edges of the oases or wadis. Most of the species are to be found in open spots in the Mediterranean and steppe habitats of North Africa and the Middle East, or along roads and on the beach in the tropics ( Côté d’Ivoire and southern India). An exceptional range of behaviour is shown by the diehlii complex with is is, which can be found foraging in full sunshine in Chotts of the Middle East or in the deserts north of Basrah (Iraq) and diehlii , living in stony deserts at higher altitudes of North Africa ( Wehner, 1986).

Comments

The bicolor species-group includes the very obvious, large, generally red-black bicoloured ants in the southwestern parts of the palaearctic, which run individually in full sunshine in open spots. Workers have been extensively collected and are present in all ant collections. The first description dates from 1787 and since then many new names have been added. The workers are rather variable and most of the characters are number of hairs, shape of petiole or colour, which have rarely been assessed but in which the ranges of variation seem to be overlapping between the individual species. Nevertheless, large samples might provide information on the variation of populations and the distribution of particular characters, such as the coloration ( Wehner et al., 1983, map 2) or the variation of the shape of the petiole ( Wehner, 1983) and so lead to a better understanding and diagnosis of species. Analysis of the secretions of the mandibular and the Dufour’s gland within the bicolor species-group support the existing morphologically based system ( Morgan et al., 1990, and personal communication).

Our current understanding of the bicolor species-group is based on male genitalia characters. The proposed system allows at least the recognition of the following species-complexes but more detailed studies are needed to investigate the limits of the male genitalia characters at species level (Agosti, unpublished). In due course it will be possible to discover the identity and variation of the characters of the workers from series with associated males. C.lunaticus , known only from two workers, is included in this species-group, as the characters mentioned, such as relative length of the maxillary palp segments, structure of the proventriculus, presence of a particular setae pattern on the hypopygium, fall within the limits of variation of the bicolor species-group presented here (Agosti, unpublished). The nocturnal habit, inferred from the yellowish colour, which would make this species unique within the genus ( Urbani, 1969), is rather doubtful as the yellow species of the lividus species-complex are mong the most heliophilous species and more material from Anatolia with rather uniform redyellowish workers and females is available in CCAC, CDA and BMNH.

The following species-complexes are either diagnosed by characters based on workers or in their absence by male genitalia characters. At least in the latter, a species-complex might be a species. As not all males are known, the proposed species-complexes might be arbitrary.

The species-complexes are diagnosable as follows:

(i) abyssiniens complex: monotypic with bicoloured workers with a low and elongate petiole. Males unknown. Distribution: southern Arabian peninsula, Ethiopia.

(ii) bicolor complex: bicoloured workers which have apressed white to yellow pubescence on the hind tibiae; the male genitalia with the stipes in lateral view convergent (Fig. 44) and with subequal distal appendices of the subgenital plate, a curved serrated face of the sagitta (Fig. 71) and its pointed median appendix. Distribution: North Africa to Côté d’Ivoire, eastern limit probably Libya.

(iii) diehliicomplex: male genitalia having the stipes in lateral view apically subparallel (Fig. 43) and with a z-shaped sagitta (Fig. 70), the same as in the niger complex but with smaller large worker (AL <4 mm; AL <5 mm in the niger complex), and a shorter first funiculus segment (FI <150; FI> 160), the workers are jet black, bicoloured to bright yellow (undescribed species from Oman, CCAC) often variable in behaviour and coloration within the same locality. Distribution: Middle East, including the Arabian peninsula and North Africa, usually on hard dry soils or in chotts.

(iv) niger complex: dark red to black workers, sometimes with a dark red patch on head and pronotum (see also above); petiole anterodorsally flattened; male genitalia with the stipes in lateral view subparallel (Fig. 45) and with a curved serrated face of the sagitta and a blunt median appendage (Fig. 72). Distribution: Egypt and Middle East, Saudi Arabia.

(v) nodus complex: male genitalia having the stipes convergent (Fig. 46) and with three distal appendices of the subgenital plate which are of equal length, a straight serrated face of the sagitta and an apically rounded median appendix of the sagitta (Fig. 73); workers bicoloured and large (AL <5 mm). Distribution: in the steppe habitats of eastern Europe, Greece, Anatolia and Caucasus to the Kopet dag, Turkmeniya, southern India (Cape Comorin, BMNH).

(vi) setipes complex: males with subequal distal processes of the subgenital plate with the median shortest (Fig. 24), a parallel sided, elongate stipes (Fig. 47) in lateral view, smoothly curved serrated face of the sagitta and a short, apically rounded median appendix of the sagitta (Fig. 74); large workers large (AL <5 mm); bicoloured with thick, bristle-like black pubescence on the hind tibiae. Distribution: Morocco and Ghana to Central Asia and the Ganges river.