Aphaenogaster senilis

Observed on open, sunny locations: forest edges, lawns, fields with scattered shrubs, urban areas. Nest in soil, mostly sheltered by stones; workers are individual foragers on the ground, in herbs and bases of trees and shrubs. Fast moving after disturbance. Aphaenogaster senilis is an important seed disperser.

Identification
A member of the A. testaceopilosa group. Boer (2013) - Workers and gynes have one funiculus segment more than the other species of the A. testaceopilosa-group, just as in Aphaenogaster gemella. Antennal club of male is 6–8-segmented (indistinct club), instead of a distinct 5-segmented club, again just as in A. gemella. The species resembles A. gemella very much. The main difference in all castes is the absence of propodeal spines or knobs in A. gemella.


 * Key to European Aphaenogaster workers

Distribution
The original description of this species was based on Sardinian specimens (Mayr 1853). On the island it seems confined to the southernmost provinces, where it is often abundant. However, it is a West-Mediterranean taxon, widespread from the Canary Islands to southern France and especially common in the Iberian Peninsula (Cagniant et al. 1991; Rigato & Toni, 2011).

Distribution based on Regional Taxon Lists
Palaearctic Region: Balearic Islands, Canary Islands, France, Gibraltar, Iberian Peninsula, Italy, Portugal, Slovakia, Spain.

Biology
Worker numbers average 1.260 &plusmn; 69 (mean &plusmn; SE, n=168, range 121-3.906) (Boulay et al. 2007). Nest density was found to be 174 nests ha-1 at a site in southern Spain. Foraging is strictly diurnal and occurs from February to November. Colonies move their nests frequently, occupying open areas in spring and fall and shady sites during the heat of the summer (Barroso et al. 2013)

Reproduction
Aphaenogaster senilis produces new colonies via fission. Monogynous. Sex ratios are highly male biased (172:1, numerically). Workers can have functional ovaries and are likely able to produce males from their eggs, provided these are allowed to develop. Queens are hypothesized to produce pheromones that suppress the production of new sexuals (Boulay et al. 2007).

Microsatellite markers revealed that the single queen mates with only one foreign male (Chéron et al. 2009). Thirty colonies were experimentally orphaned, and workers reared 2.0 &plusmn; 1.1 gynes from the previous queen’s diploid brood, with 10 groups producing one gyne and 20 groups producing two to five gynes. The firstborn gyne emerged on average 17 days before the second. Behavioural observations showed that gynes interacted aggressively and the firstborn gyne was always dominant. She was usually the only one to survive, even though gynes did not differ in weight (Chéron et al. 2009). Such low colonial investment in gyne production is consistent with colony fission (Cronin et al. 2013 PDF).

Chemistry
The contents of the Dufours gland and postpharyngeal gland have been examined for workers and queens (Boulay et al. 2007)

Castes
Gynes have short wings but cannot fly (Tinaut & Ruano 1992), while males can fly from their nest; hence mating occurs in or near the natal nest of gynes.

Nomenclature

 *  senilis. Aphaenogaster senilis Mayr, 1853b: 108 (w.q.) ITALY. Emery, 1916b: 140 (m.). Junior synonym of testaceopilosa: Nylander, 1856b: 86; Smith, F. 1858b: 165 (misspelled as similis); Roger, 1859: 255; Dalla Torre, 1893: 107. Subspecies of testaceopilosa: Emery, 1878b: 53; Emery, 1916b: 131; Santschi, 1919e: 245. Revived status as species: Bondroit, 1918: 161; Santschi, 1933c: 396; Cagniant, 1964: 100; Bernard, 1967: 132. Baroni Urbani, 1971c: 44. Senior synonym of acoreensis: Yarrow, 1967: 26; of fuentei: Collingwood, 1978: 67; of occidua: Casevitz-Weulerrse & Galkowski, 2009: 486; of grata, occidua: Boer, 2013: 81. Current subspecies: nominal plus disjuncta.
 * acoreensis. Aphaenogaster senilis var. acoreensis Santschi, 1933a: 21 (q.) AZORES IS. [Also described as new by Santschi, 1933c: 397.] Junior synonym of senilis: Yarrow, 1967: 26.
 * fuentei. Aphaenogaster testaceopilosa var. fuentei Medina, 1893: 105 (w.) SPAIN. Junior synonym of senilis: Collingwood, 1978: 67.
 * grata. Aphaenogaster senilis var. grata Santschi, 1933c: 397, fig. 34 (m.) SPAIN. Junior synonym of senilis: Boer, 2013: 81.
 * occidua. Aphaenogaster senilis var. occidua Santschi, 1933c: 396, fig. 26 (w.m.) FRANCE. Junior synonym of senilis: Casevitz-Weulerrse & Galkowski, 2009: 486, Boer, 2013: 81.

Description
Boer (2013) :

Worker
Lateral sides of pronotum and metanotum without or with weak longitudinal rugulae, propodeum with distinct longitidinal rugulae. Rugulose sculpture on dorsal side absent. Head in full-face view with longitudinal rugulae, here and there with some cross-connections. Mesosoma, head in full-face view, dorsal and lateral sides of petioles punctate. Legs of different individuals are showing a transition from punctulation to microreticulation. Ventral to the propodeal spines punctate and sometimes transversely costulate. Dorsal side of postpetiole with longitudinal costulae. Dorsal side of base of gaster with transverse microstriae. Head, pronotum, terminal side of propodeum, beneath the propodeal spines, lateral sides of petioles and dorsal side of the gaster matt. Dorsum postpetiole wax gloss to matt. Lateral sides of gaster satin. Dorsal side of petiole matt to wax gloss. Antennal club 5-segmented. Petiolar node with rounded top. Petiole equal in height as postpetiole or somewhat higher. Spur of hind tibia with minute dentation.

Measurements (n = 33). CI 71–84 (76); CW 1.18–1.46 (1.29) mm; CL 1.50–1.87 (1.71) mm; PHI 31–35 (32); PI 72–93 (81); PPPI: 43–54 (48); PSI 112–167 (135); PSLWI 95–188 (121); PWI 20–43 (24); RPH 121–153 (139); RPSI 11–44 (30); SI 129–149 (141); SL 1.70–1.89 (1.83) mm; SPD 1–3 (1.7); SPL 4–6 (4.9).

Queen
Head in full-face view, including occiput, with longitudinal rugulae with cross-connections. Longitudinal rugulae on clypeus, head and anterior side of the postpetiole and lateral sides of the mesosoma. Transverse rugulae on pronotum (partly), propodeum and terminal sides of petioles. Pronotum (partly), mesoscutum and scutellum scabriculous. Punctation on head, mesosoma and petioles (including anterior part of the petiole). About 30 transverse microstriae in the midline of the first gastral tergite near the base. Mesosoma dorsally matt, gaster dorsally matt satin to satin. Antennal club 5-segmented. Wings with a light yellowish tint. Scutellum rises weakly above the mesoscutum and does not bend over themetanotum.

Measurements (n = 3). CI: 83–87; CL: 1.82–1.86 mm; CW: 1.50–1.61 mm; OCI: 29–37 (33); PHI 44–47; PI 64–68; PPPI 78–88; PSI 208–280; PSLWI 104–110; PWI 30–35; RPH 135–157; RPSI 57–67; SI 114; SI/CI: 132–138; SL 1.70–1.84 mm; SPD 1; SPL 4–5.5.

Male
Rugulae are absent on the whole body. Whole body punctate, except the propodeum and gaster. No microstriae on first gastral tergite. Clypeus with transverse rugulae. Head, pronotum and mesonotum matt. Lateral sides of mesosoma (partly) and propodeum shiny. Petioles and dorsal side of gaster glossy to shiny. Lateral sides of gaster shiny. Antennal club 6–8-segmented (indistinct club). Pubescence on hind tibia suberect, their length longer than the diameter of the tibia. Wings clear. Scutellum slightly erect above mesoscutum, partly bent over metanotum. Mandible with one large apical tooth, tooth 2 and or 3 relatively large, rest of the masticatory margin of the mandibles distinctly dentate. A longitudinal groove between the two knobs at the terminal side of the propodeum. These knobs are dorsally flattened, diagonally to the rear. Ventral to the propodeal stigma are the metapleural gland bullae, which are extremely developed into broad discuslike, sharp ending knobs, bowed in the lateral direction, and slightly deflected in the more ventral direction.

Measurements (n = 7). CI 85–91 (89); CL 0.90–1.08 (1.03) mm; CW: 0.81–1.00 (0.91) mm; EYI 37–43 (39); OCI 44–56 (51); SL/CL 32–36 (33); SL 0.29–0.37 (34) mm.

Type Material
Holotype: male of A. senilis grata: Spain: Parla (Madrid), 28.v.1927 (Dusmet, ). Syntypes: of A. senilis occidua: France: Banyuls (Pyr. Or.), vii.1932, 5 workers, 4 males (Denis, NHMB).