Sericomyrmex parvulus

Most collections of this species have been from forested areas. The biology of Sericomyrmex parvulus has not been studied, general details about the biology of the genus are given here.

Identification
Ješovnik & Schultz (2017) - Small species; posterior cephalic corner smoothly rounded; frontal lobe triangular, small, narrow; frontal carina faint, incomplete; mesosomal tubercles small, low, first gastral tergite with lateral carinae weakly developed, dorsal carinae absent.

The aptly named S. parvulus is the smallest Sericomyrmex species. In the regions where their distributions overlap, parvulus is most easily mistaken for Sericomyrmex opacus. In general opacus is larger, with wider, rectangular frontal lobes. Similarly, the S. opacus queen can be separated from the parvulus queen by its slightly larger size and by the presence of supraocular eye carinae in some specimens (absent in parvulus). The queen of Sericomyrmex saramama is similar in size but can be recognized by its striate mandibles (smooth in parvulus).

Within-species morphological variation in S. parvulus includes the frontal carinae (typically incomplete and faint, but complete and stronger in some populations), eyes (sometimes covered with a white layer, but sometimes not), and the general robustness of denticles and tubercles on the mesosoma and metasoma.

Distribution
Ješovnik & Schultz (2017) - Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Peru, Suriname.

Distribution based on Regional Taxon Lists
Neotropical Region: Brazil, Guyana, Suriname.

Biology
Castano-Meneses et al (2017) - The springtail species Cyphoderus agnotus Börner (Cyphoderidae: Cyphoderus) and Cyphoderus similis Börner (Cyphoderidae: Cyphoderus) are known from nests of this ant.

Castes
Jesovnik and Schultz 2017. Figure 48. S. parvulus worker and queen; head, lateral profile, and dorsal view. Worker (USN-MENT00446157) (a, c, e). Queen (USNMENT01125594) (b, d, f). Figure 49. S. parvulus worker (USNMENT01125593), SEM images. a Head, full-face view b mandibles c mesosoma and metasoma, lateral view d eye.

Jesovnik and Schultz 2017. Figure 50. S. parvulus larva (USNMENT01125592), SEM images. a Lateral view b ventral view c head, frontodorsal view d head, lateral view e mouthparts f anal setae.

Nomenclature

 *  parvulus. Sericomyrmex parvulus Forel, 1912e: 193 (w.) BRAZIL.
 * Ješovnik & Schultz, 2017a: 82 (q.l.).
 * Status as species: Wheeler, W.M. 1916c: 11 (in key); Emery, 1924d: 339; Borgmeier, 1927c: 128; Kempf, 1972a: 229; Bolton, 1995b: 382; Ješovnik & Schultz, 2017a: 80 (redescription).
 * Senior synonym of myersi: Ješovnik & Schultz, 2017a: 80.
 * myersi. Sericomyrmex myersi Weber, 1937: 400 (w.) SURINAM.
 * Status as species: Weber, 1946b: 143; Kempf, 1972a: 229; Bolton, 1995b: 382.
 * Junior synonym of parvulus: Ješovnik & Schultz, 2017a: 80.

Ješovnik & Schultz (2017) - In populations of S. opacus from southern Colombia and northwestern Brazil, some of the workers have small, triangular frontal lobes, making them easy to mistake for parvulus. They are usually larger than the typical parvulus worker, but given the overlap in size between the two species, they could be mistaken for larger parvulus workers. It is possible that these intermediate individuals are hybrids and that the molecular and morphological differences between the Colombian and Brazilian populations of opacus are a consequence of hybridization and introgression with parvulus.

Description
Ješovnik & Schultz (2017):

Worker
(lectotype): HWe 0.66–0.9 (0.9) HW 0.66–0.93 (0.93) HW1 0.6–0.93 (0.84) HW2 0.68–1.03 (0.93) HW3 0.48–0.8 (0.6) IFW1 0.42–0.65 (0.62) IFW2 0.15–0.28 (0.26) HL1 0.62–0.9 (0.88) HL2 0.58–0.82 (0.8) SL 0.48–0.72 (0.64) EL 0.11–0.15 (0.15) Om 6–9 WL 0.74–1.23 (1.23) PL 0.16–0.34 (0.25) PPL 0.13–0.24 (0.16) GL 0.6–0.9 (0.83) HFL 0.65–0.99 (0.92) PW 0.46–0.64 (0.62) CI 94–106 (103) FLI 60–75 (69) SI 64–78 (71) OI 13–19 (17) CEI 5–12 (8) [N=55]

Pilosity. Pubescence dense, lighter than integument, appressed to decumbent. Hairs moderately thick, relatively sparse, often curved, yellow to gray, appressed to suberect.

Head. In full-face view evenly broad and long (CI=102 ± 3), posterior corner smoothly rounded, posterior cephalic emargination shallow (CEI=9 ± 2), gradually impressed. Vertexal impression faint, frontal tumuli barely visible. Mandible with 7–8 teeth, dorsally smooth and glossy, finely transversely striate only along masticatory margin. Eye medium-sized (OI =16 ± 1), flat to slightly convex, 6–9 ommatidia across largest diameter, in some specimens eyes partially covered with white layer (Figure 6l), in others eyes without white layer. Frontal lobe triangular, relatively small and narrow (FLI=70 ± 3), posterior margin shorter than medial. Frontal carina straight to slightly curved laterally, incomplete, weak, fading before reaching posterior cephalic corner. Antennal scape relatively short, not reaching posterior cephalic corner (SI=71 ± 3).

Mesosoma. Mesosomal tubercles low and obtuse. Propodeal carinae low and weak, with small posterodorsal denticles.

Metasoma. Petiole with two low, reduced dorsal denticles; postpetiole with two faint, short dorsal carina; both best seen in dorsolateral view. First gastral tergite with lateral carinae weakly developed, dorsal carinae faint or absent.

Queen
HWe 0.98–1.05 HW 1–1.08 HW1 1–1.13 HW2 1.08–1.22 HW3 0.74–0.8 IFW1 0.7–0.78 IFW2 0.24–0.28 HL1 0.95–1.08 HL2 0.88–0.95 SL 0.64–0.7 EL 0.21–0.24 Om 14–15 EW 0.08–0.08 WL 1.56–1.65 PL 0.34–0.48 PPL 0.2–0.25 GL 1.4–1.58 HFL 1–1.18 PW 0.82–0.92 CI 95–103 FLI 72–76 SI 66–70 OI 21–23 [N=4]

Head. Mandible with 7–8 teeth, dorsally glossy and smooth, finely transversely striate only along masticatory margin. Preocular carina fading posterior to eye. Eye large (OI=22 ± 1), mildly convex, 14–15 ommatidia across largest diameter. Frontal lobe more robust than in worker, antennal scape not reaching posterior cephalic corner. Mesosoma. Lateral pronotal tubercles very low. Scutum in dorsal view with notauli and median mesoscutal line absent or very faint. Parapsidal lines faint, slightly curved. Axillae small, groove separating axillae from scutellum smooth. Scutellum short in dorsal view, narrowing posteriorly, posterior margin with V-shaped notch, notch sometimes continuing into median impression that divides scutellum in two lateral parts. Propodeal denticle low, obtuse, laterally flattened, diverging posteriorly in dorsal view.

Metasoma. First tergite of gaster with lateral carinae well developed, dorsal carinae absent or weak, anteromedian groove shallow.

Larva
Lateral and dorsal surfaces without any setae. Supra-antennal setae absent. Four genal setae on each side. Mandibular apical tooth undivided. Labial denticles either absent or small number of denticles present anterior to sericteries. Thoracic segment 1 (T1) ventrally with multidentate spinules. Number of ventral setae: T1, T2, and T3 with two setae each, abdomen without setae (not including anal setae). Single pair of sensilliform setae anterior to anal opening.

Type Material
Lectotype worker (here designated): Brazil, Pará, [-4, -53] C. Emery (: 1w, USNM00445579, bottom specimen). Paralectotype: same data as lectotype (MHNG: 1w, USNM00445579, top specimen).