Strumigenys waiwai Sosa-Calvo, Schultz, and LaPolla, 2010

Jeffrey Sosa-Calvo, Ted R. Schultz & John S. Lapolla, 2010, A Review of the Dacetine Ants of Guyana (Formicidae: Myrmicinae), Journal of Hymenoptera Research 19, No. 1, pp. 11-43 : 30-34

Strumigenys waiwai Sosa-Calvo, Schultz, and LaPolla , n. sp. ( Figs 40–47 )

Material examined.— Holotype: worker, labeled ‘‘ GUYANA: Upper Takutu-Upper Essequibo, Acarai Mountains, camp edge Kamoa River , 394 m., 58 ° 49.929 ' W, 1 ° 32.786 ' N; 22.x.2006; J. Sosa-Calvo, T.R. Schultz; 1 ° forest; leaf-litter sample. (TRS 061022-LS04) ’’ USNM ENT No. 00537291 . (UGBC). Paratypes: 2 workers, same locality as in holotype . USNM ENT No. 00537290, 00537292 ; 1 worker, labeled ‘‘ GUYANA: Upper Takutu-Upper Essequibo, Acarai Mountains, camp edge Kamoa River , 530 m., 58 ° 50.299 ' W, 1 ° 33.046 ' N; 24.x.2006; J. Sosa-Calvo, T.R. Schultz, C.J. Marshall, R. Williams; 1 ° forest; leaf-litter sample. (JSC 061024- LS10) ’’ USNM ENT No. 00537293 . ( USNM).

Diagnosis (worker). — Small ( TL 1.35– 1.45); cephalic margin with multi-furcate hairs; leading edge of antennal scapes at least with one hair that curves towards base of scape; eyes small, consisting of two or three ommatidia; inner margin of mandibles with a pair of spiniform teeth and a minute but conspicuous pair of teeth at midlength of mandibles; ventral margin of petiole with angular ventral process. In some workers (paratypes) ventral process of petiole very reduced.

Description (worker). —Head: leading edge of antennal scapes with at least one hair curving toward base of antennal scape; hairs on leading edge of antennal scapes narrowly spatulate or simple; inner margin of mandibles with pair of preapical spiniform teeth close to apicodorsal tooth and minute but conspicuous pair of teeth at midlength of mandibles; anterior margin of clypeus slightly concave ( Figs 40, 42 ); dorsum of clypeus finely reticulate; dorsum of head markedly areolate and with multi-furcate hairs on posterior occipital portion ( Figs 40–41, 43 ); upper margin of scrobes with row of simple hairs that curve anteriorly and with two flagellate hairs, one of which is in apicoscrobal position; eyes very reduced, with 2 or 3 ommatidia; ocular carina weakly developed, short and not reaching level of eyes; cephalic dorsum, in profile, with 2 pairs of inconspicuous erect simple hairs, very difficult to see and perhaps fragile and easily lost but differing from bifurcating pilosity that surrounds them. Mesosoma: dorsum of promesonotum, propodeum, and declivity of propodeum strongly areolate; dorsum of pronotum with elongate pair of hairs in addition to those at humeri; humeral hair flagellate; promesonotal spiracle in dorsal view projecting laterally, giving pronotum wider appearance and mesonotum and propodeum narrower appearance; mesonotum with pair of elongate hairs; sides of pronotum and anepisternum strongly areolate; mesopleuron and metapleuron mostly smooth and shining; dorsum of promesonotum and propodeum with simple subdecumbent hairs; propodeal spines minute and acute, subtended by broad lamella on declivity. Metasoma: dorsum of peduncle, disc, and sides of petiole strongly areolate; in lateral view, petiole with long ventral process. In one worker (paratype) ventral process reduced to small tooth ( Fig. 43 ); petiole, in lateral view, subquadrate; sides of petiole, in dorsal view, with conspicuous triangular crest; postpetiole, in lateral view, with large ventral spongiform lobes; disc of postpetiole with some longitudinal rugae; areas between rugae smooth and shining; dorsum of postpetiole with decumbent hairs; first gastral sternite with pad of spongiform tissue; first gastral tergite smooth and shining, with some conspicuous longitudinal basigastral costulae, barely as long as disc of postpetiole; first gastral tergite mostly with subdecumbent and decumbent hairs and some erect hairs (lacking in some paratype specimens. It is probable that these hairs are very fragile and lost easily).

Measurements: holotype (and paratypes): GL = 0.31 (0.28–0.31), HL = 0.33 (0.31– 0.34), HW = 0.26 (0.25–0.26), ML = 0.18 (0.18–0.19), PL = 0.17, PPL = 0.08 (0.08– 0.09), PW = 0.16 (0.14–0.16), SL = 0.21 (0.19–0.21), TL = 1.44 (1.35–1.45), WL = 0.36 (0.32–0.36). Indexes: CI = 79 (76–80), MI = 55 (53–58), PI = 48 (47–51), SI = 81 (77–82). (n = 4)

Gyne and male.— Unknown

Etymology.— This species is named after the Wai-Wai indigenous people, who depend on the area where we collected this species for their sustenance. Without their guidance, support, and permission to conduct research on their land, this work would not have been possible.

Comments.— Strumigenys waiwai is most similar to members of the Neotropical silvestrii -group. Strumigenys waiwai shares with most of the 18 known species in this group the following characters: (i) the small size ( HL 0.31–0.34, HW 0.25–0.26, TL 1.35–1.45, WL 0.32–0.36. In members of the silvestrii -group HL 0.36–0.52, HW 0.28– 0.44, TL 1.5–2.2, WL 0.36–0.56); (ii) the absence of intercalary tooth between the apicodorsal and apicoventral teeth in the apical fork of the mandibles (this character state is shared with all the species in the group, except for S. xochipili Bolton from Mexico, which possesses a single intercalary tooth); (iii) the presence, on the inner margin of mandibles, of a spiniform pair of preapical teeth close to the apicodorsal tooth of the apical fork and, in addition, a minute pair of denticles on the midlength of the mandibles that may be difficult to see; (iv) the antennal scapes short to moderate ( SI 76–80. In members of the S. silvestrii species group the SI 62–91), and with some hairs on the leading edge of the antennal scape that are curved toward the base of the scape; (v) the eyes very small, commonly formed by 1–3 ommatidia in total (some members of the S. silvestrii species group with 6 or more ommatidia);.

(vi) the preocular carina short or weakly developed, ending before level of the eye; (vii) the propodeum, in profile, usually with a triangular pair of teeth that are subtended by a lamella or carina that extends down the declivity; and (viii) ventral surface of petiole lacking spongiform tissue instead with a small, but conspicuous crest or ventral process (members of the silvestrii -group usually lack spongiform tissue on ventral margin of petiole except for the species S. nastata Bolton, S. perdita Bolton, and S. calamita Bolton).

Variations in the presence of standing erect hairs on the cephalic dorsum were observed in the specimens studied (holotype and paratypes). In the material examined, some workers of S. waiwai have the two pairs of erect simple hairs on the dorsum of head that differ from the cephalic ground-pilosity, of which one pair is located close to occipital margin and the other is located close to the highest point of vertex. Among the variations observed in other specimens are: the two pairs of standing hairs are present, but curving at the tips, or only one pair of hairs is visible, or the hairs are difficult to see, or the hairs are missing. Apparently these hairs are very fragile and can be easily lost; therefore specimens may appear to have no hairs. Within the silvestrii -group, only individuals in the species S. calamita , S. nastata , S. perdita , and S. timicala Bolton, all endemic to Central America, share with individuals of S. waiwai the presence of two pairs of erect hairs on the cephalic dorsum, but these species differ from S. waiwai by having a fringe or curtain of spongiform tissue on the ventral margin of the petiole, whereas S. waiwai has an angular crest or small ventral process. In addition, S. waiwai differs from: S. nastata by having the antennal scape without a projecting narrow cuticular lamella that arises proximal to the subbasal bend; S. timicala by having the preapical tooth of the mandible separated from the apicodorsal tooth by a distance twice its length, rather than having the preapical tooth very close to the apicodorsal tooth; S. calamita and S. perdita by having the first gastral tergite generally with subdecumbent or decumbent simple hairs (in some specimens it is possible to see, in addition, a few erect simple hairs) rather than entirely short stout hairs that are remiform to claviform (in S. calamita ) or simple erect and stiff (in perdita ); and from all four species and any other species in the S. silvestrii -group by: (i) having the dorsolateral margin of the head with two freely laterally projecting elongate or short flagellate hairs, one of which is located at the level of the vestigial eye and the other the apicoscrobal hair. This character state is also shared with S. lanuginosa but these hairs are shorter in S. waiwai than in S. lanuginosa ; (ii) having hairs on the upper margins of the antennal scrobe simple and curving anteriorly rather than spoonshaped, spatulate, or narrowly spatulate and curving anteriorly (except for perparva in which case these hairs are posteriorly curved); and (iii) the cephalic groundpilosity composed of short erect or subdecumbent multifurcated hairs rather than spoon-shaped, spatulate, or narrowly spatulate hairs.

MODIFIED VERSION OF KEY IN BOLTON (2000)

In Bolton’s (2000) key, Strumigenys waiwai keys out to S. perdita . The key for the species of Strumigenys of the Neotropics can be modified as below to properly include S. waiwai . Numbering of couplets follows Bolton (2000).

47. In full-face view upper scrobe margin with a row of 4–5 broadly spatulate to spoon-shaped hairs that are curved posteriorly.......................... perparva

– In full-face view upper scrobe margin with row of simple or spatulate to spoon-shaped hairs that are all curved anteriorly................. couplet 48 in Bolton (2000)

48. Cephalic dorsum with two pairs of short erect hairs, one pair close to occipital margin, the other close to highest point of vertex. Ventral surface of petiole with curtain or fringe of spongiform tissue, or at least with spongiform lobes linked by carina. If spongiform tissue reduced to angular anteroventral process present, then dorsolateral margin of head with two freely laterally projecting short flagellate hairs, one at level of the vestigial eye, the other the apicoscrobal............ 49

– Cephalic dorsum without or with one pair of short erect hairs, when one is present it is close to occipital margin. Ventral surface of petiole without spongiform tissue, sometimes with rounded or angular anteroventral cuticular process. Dorsolateral margin of head without projecting flagellate hairs or with single hair, in apicoscrobal position............................ couplet 52 in Bolton (2000)

49. Distal preapical tooth conspicuous and obviously spiniform, located markedly proximal of the apicodorsal tooth and at about right angle to long axis of the mandible. Distal preapical teeth of opposing mandibles so long that their apices meet or even slightly overlap when mandibles fully closed. Mandibles always with small denticle just proximal of the inner midlength...................... 50

– Distal preapical tooth small, thorn-like and not obviously spiniform, located very close to the apicodorsal tooth and inclined toward it. Distal preapical teeth of opposing mandibles so short that their apices are widely separated when mandibles fully closed. Mandible usually without trace of denticle proximal to inner midlength but rarely vestigial denticle visible.................................. timicala

50. Leading edge of scape at subbasal bend with projecting convex cuticular lamella; lamella originates close to scape base and terminates just distal of the bend. Distal preapical tooth about same distance from proximal preapical denticle as it is from apicodorsal tooth............................................. nastata

– Leading edge of the scape at subbasal bend without projecting convex cuticular lamella. Distal preapical tooth closer to apicodorsal tooth than it is to proximal preapical denticle................................................ 51a

51a. Leading edge of antennal scape with spoon-shaped or narrowly spatulate hairs. In full-face view upper scrobe margin with row of spatulate to spoon-shaped hairs. Cephalic ground-pilosity spoon-shaped or spatulate.... couplet 51 of Bolton (2000)

– Leading edge of antennal scape with simple or filiform hairs. In full-face view, upper scrobe margin with a row of simple or filiform hairs. Cephalic ground-pilosity multifurcated...................................... waiwai new species

Figures

Figs 40–47. Scanning electron micrograph of a paratype worker of Strumigenys aeaiaeai, new species. 40, Head and mandibles in full-face view. 41, Cephalic capsule in full-face view. 42, Mandibles in dorsal view. 43, Lateral view. 44, Dorsal view. 45, Dorsal view of mesosoma. 46, Waist segments in dorsal view. 47, Postpetiole and first gastral tergite in dorsal view.