Pheidole distorta Forel, 1899

Guerrero, Roberto J., García, Emira & Fernández, Fernando, 2022, The Pheidole Westwood, 1839 ants (Formicidae: Myrmicinae) in Colombia: new records including two species with remarkable morphology, Zootaxa 5154 (3), pp. 319-332 : 322-323

Pheidole distorta Forel, 1899

Minor worker measurements (n= 10): HW 0.61–0.65, HL 0.60–0.65, SL 0.52–0.56, EL 0.12–0.14, WL 0.70–0.75, PTW 0.12–0.14, PPW 0.16–0.18, CI 97–108, SI 81–93, PPI 129–133.

Soldier measurements (n= 10): HW 1.41–1.49, HL 1.22–1.26, SL 0.57–0.63, EL 0.18–0.20, WL 1.20–1.31, PSL 0.02, PTW 0.35–0.37, PPW 0.47–0.53, CI 84–89, SI 45–51, PSLI 1, PPI 133–142.

Queen measurements (n= 10): HW 1.10–1.16, HL 0.98–1.04, SL 0.53–0.63, EL 0.20–0.31, WL 1.71–1.78, PSL 0.02, PTW 0.45, PPW 0.55, CI 108–112, SI 47–58, PSLI 2, PPI 122.

Male measurements (n= 10): HW 0.51–0.53, HL 0.57–0.59, SL 0.12–0.16, EL 0.35, WL 1.49–1.57, PTW 0.20, PPW 0.24, CI 87–93, SI 22–27, PPI 120.

Diagnosis. Pheidole distorta is distinguished from the rest of the members of the distorta group by the short or absent propodeal spines. Other species have longer propodeal spines.

Description. Minor worker: head, pronotum, propodeum and gaster smooth and shiny; developed pronotal shoulders; promesonotal hump-shaped bulge, with a pair of tubercle-shaped protrusions; katepisternum foveatereticulated, most often with a smooth, shiny patch in the middle. Soldier: head strongly rugoreticulate, forming an areolate and shiny surface, with a shallow depression in the middle part; mesosome surface like that on the head; in profile, petiole with developed longitudinal ventral process; dorsum of first gastral tergite opaque, longitudinally costulate, the costulae fading towards an anterior quarter of the tergite; very fine granular microsculpture extending in the posterior region of the first tergite. Queen (previously undescribed): reddish-brown ants with shiny surface; punctuation and rugoreticulated sculpture on the head, forming an areolate surface; scape strongly angled towards the base; strongly curved hypostomal margin, with a reduced middle tooth, barely protruding by a blunt bulge, absent inner hypostomal teeth, short and pointed outer hypostomal teeth; mesomal sculpture as on the head, except for the anterior part of the anepisternum and katepisternum which lack rugoreticulae; propodeum with reduced propodeal spines, forming an obtuse angle; petiole with developed longitudinal ventral process. Male (previously undescribed): head covered with longitudinal carinae and conspicuous punctuation; compound eyes protruding from the cephalic margins; yellow mandible, with brown masticatory margin, a single developed apical tooth and blunt to semi-square basal tooth; short scape, with globose pedicel; in ventral view, head with transverse costulae extending from the postgenal suture towards the eyes, surface with conspicuous punctuation; in profile view, 1/3 of the posterior part of the anepisternum with punctuation and fine costulae; axilla covered with fovea; propodeum with a foveate surface and sparsely costulate, devoid of angles that resemble a propodeal spine; petiole with longitudinal process less developed than in the queen.

Material examined. Colombia, Magdalena: 18 soldiers, 48 minor workers, 2 queens, Santa Marta, campus Universidad del Magdalena, shade of trees, hard ground, 11.2246, -74.1853, 14. May. 2019. Coll. M. Escárraga, hand collecting, nest # 1[CBUM]; 8 soldiers, 16 workers, same data except by nest excavated in hard soil, 2. Jun. 2019. Coll. M. Escárraga & E. García, nest # 2 [CBUM]; 26 soldiers, 37 minor workers, 1 queen, 116 males, Santa Marta, Universidad del Magdalena, nest excavated in hard soil, 11.2246, -74.1853, alt. 25m, 6. Jul. 2019. Coll. M. Escárraga & J. Roncallo, nest # 3 [CBUM]; 8 soldiers, 55 minor workers, 93 alate queens, 1 queen, same data except by Coll. E. García & H. Sierra, nest # 4 [CBUM].

Comments. This species is known only from northern Colombia. The minor workers and soldiers of Pheidole distorta examined here are identical to the minor worker (CASENT0908310) and soldier (CASENT0908309) syntypes imaged on AntWeb. We observed an additional distinctive character of P. distorta : the soldier, queen, and male have a longitudinal ventral process on the petiole.

Pheidole distorta was known only from the type specimens used by Forel (1899), with no further specimens deposited in museums or other biological collections. During field work within the Universidad del Magdalena campus, we detected several nests of P. distorta in an area smaller than 100 m 2. These nests were excavated and contained minor workers, soldiers, males, and delate/alate queens.

The excavation of ant nests not only favors the possibility of associating castes to the same species (e.g., soldiers and minor workers in Pheidole ) but also the possibility of understanding the colonial structure of species ( Buhl et al. 2004; Forti et al. 2007). A finding from the excavation of Pheidole distorta nests documented in this study is related to the asymmetric sex ratio found in the colonies. We found colonies exclusively producing males or females (alate queens) in different nests during the same dry climatic season, with a single queen in each of these nests (i.e., monogynic colonies). The production of males or females in different nests has apparently not been documented in species of ants that inhabit the dry forest. This behavior has also been found in other Pheidole species in Santa Marta, such as Pheidole fallax Mayr, 1870 and Pheidole urbana Camargo-Vanegas & Guerrero, 2020 ( Guerrero et al. unpublished data). The data provided here provide base line for analyzing the factors that can promote and determine the reproductive phenology of Pheidole distorta populations in this forest type. Identification of flight patterns in taxocenes, as well as mechanisms driving the reproductive phenology of populations of dry forest ant species, would allow us to continue understanding the evolution of the taxonomic diversity of this type of ant assemblage.