Camponotus micronesicus , Ronald M. Clouse, Benjamin D. Blanchard, Rebecca Gibson, Ward C. Wheeler & Milan Janda, 2016

Ronald M. Clouse, Benjamin D. Blanchard, Rebecca Gibson, Ward C. Wheeler & Milan Janda, 2016, Taxonomic updates for some confusing Micronesian species of Camponotus (Hymenoptera: Formicidae: Formicinae), Myrmecological News 23, pp. 139-152: 147-149

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Camponotus micronesicus


Camponotus micronesicus  sp.n. BLANCHARD & CLOUSE ( Figs. 21 ­ 29; Tab. 4)

Type material: Holotype major worker, Federated States of Micronesia: Pohnpei Island, Nah Islet , 1 m a.s.l. (6º 51' 11.2" N, 158º 21' 16.3" E), 15. IX. 2010, leg. R. Clouse and P. Sharma.GoogleMaps  Paratypes (8 major workers, 8 minor workers), detailed collection information provided in Table 4. All specimens are deposited in the Museum of Comparative Zoology, Harvard University, Massachusetts, USA.

Description of holotype major worker ( Figs. 21 ­ 23): EL 0.55, EW 0.40, FCL 1.30, HL 2.50, HW 2.25, ML 3.00, MTL 1.80, PH 0.85, PL 0.65, SL 1.95; CI 90, SI 87.

Masticatory margin with six teeth that diminish in size unevenly from the apical tooth; teeth 2 ­ 5 similar in size, sixth tooth (not visible when mandibles closed) distinctly smaller. Clypeus continuing anteriorly past mandibular insertions one fourth its total height, then slightly convex. Posterior margin of clypeus straight to slightly concave, antennal insertions separated from clypeus by a distance almost equal to the distance from nearest clypeal margin to clypeal midpoint. Posterior head margin weakly concave to nearly flat. In frontal view: eyes located halfway between posterior clypeal margin and vertex; inner eye margins halfway between frontal lobes and sides of head; eyes not extending past lateral margin of head. Antennae 12­ segmented. Antennal scape reaching past the posterior margin of head by a distance 1 ­ 2 times the width of the scape at its apex. Mesosoma in profile gently sloping from anterior pronotum to dorsal propodeum, with slightly steep­ er propodeal declivity. Petiolar node sloping evenly up to and down from its apex.

Color: Gaster and mesosoma uniformly yellow­orange, the head ranging from slightly to considerably darker orange­brown. Vertex to posterior frons and anterior frontal lobes orange brown, anterior frons and clypeus yelloworange; central posterior head and frontal carina dark orange brown. Mandibles dark reddish brown, lighter at insertions, mandibular teeth black. Each gastral tergite with hyaline margin along posterior fifth.

Pilosity: Layer of small, recumbent, light hairs all over head. Longer, standing hairs numerous on front, back, and sides of head, longer at vertex and more dense on clypeus. From frontal view, area between eyes and frontal carina, two rows of long, standing hairs extending from vertex to mid­clypeus. Dorsal pronotum, mesonotum and vertex of propodeal angle with long standing hairs. Propleuron standing hairs lacking. Each gastral tergite with 10 to 20 long standing hairs encircling tergite immediately before hyaline margin along posterior edge; 5 to 10 longer standing hairs encircling tergite halfway between hyaline margin and posterior edge of previous tergite. Hind femur standing hairs lacking.

Sculpturing: Head, mesosoma, and gaster surface glossy; genae, clypeus, and mandibles weakly punctured.

Description of paratypes: Majors resembling holotype in coloration and pilosity, mesosoma ranging from light yellow to orange­yellow, heads sometimes distinctly darker than mesosoma but not brown. Generally same size or smaller than holotype (ML 2.65 ­ 3.00, HW 1.85 ­ 2.30), with similar head shapes (CI 86 ­ 92). Relative scape lengths more variable (SI 83 ­ 98). Minors approximately 15% ­ 20% smaller than majors (ML 2.2 ­ 2.5) but with much narrower heads (CI 67 ­ 74) and proportionally longer, more variable scapes (SI 175 ­ 191). Mesosoma coloration more consistently light yellow with similar or only slightly darker heads. Occipital carina always present. Measurements of minor worker collected with holotype and shown in Figs. 24 ­ 26 View Figure : EL 0.40, EW 0.30, FCL 0.95, HL 1.35, HW 1.00, ML 2.30, MTL 1.50, PH 0.51, PL 0.50, SL 1.85; CI 74, SI 185.

Differential diagnosis: In Micronesia there are four closely related Camponotus species that resemble C. maculatus (characters for which are described and illustrated in MCARTHUR & LEYS 2006): C. micronesicus  sp.n., C. eperiamorum, C. kubaryi stat. rev., and C. tol  sp.n. Of these species, only C. micronesicus  sp.n. is mostly concolorous yellow­orange, and with the other three species being island endemics, C. micronesicus  sp.n. can be collected alongside only one of them at a time ( CLOUSE 2007a). In Melanesia collections of C. micronesicus  sp.n. are near those of three other described C. maculatus ­like species: C. choloroticus, C. novaehollandiae, and C. humilior. However, only the latter two share the lack of propleuron and hind femur standing hairs with C. micronesicus  sp.n., and although uniformly yellow­orange specimens of C. humilior and C. novaehollandiae are occasionally seen, both species tend to be strongly bicolorous. Moreover, the head length and width measurements for both majors and minors of C. novaehollandiae are approximately 25% larger than those of C. micronesicus  sp.n., and we have no evidence that the ranges of these species overlap exactly with C. micronesicus  sp.n. (C. humilior and C. novaehollandiae enter New Guinea only along the southern coast, where we have no C. micronesicus  sp.n. collections).

The most difficult cases of identification will be between Camponotus micronesicus  sp.n. and C. chloroticus  specimens collected from Vanuatu, where they are sympatric and look nearly identical. Our best advice for identification is to check for hairs on the propleuron and hind femur, which should be absent in C. micronesicus  sp.n. and present in C. chloroticus  . In addition, C. chloroticus  minors usually have a larger cephalic index (74 ­ 8 2 vs.67 ­ 74) and smaller scape index (123 ­ 154 vs. 175 ­ 191), both resulting from having a wider head; majors show the same trend, although those of C. chloroticus  are highly variable ( Tab. 2).

Habitat: This species is found in disturbed forest, both natural (e.g., reef islets, which are washed over during heavy storms) and anthropogenic (e.g., agroforest at low and middle elevations).

Etymology: This species is named for Micronesia, the predominant region where it is found.

Comments: All paratypes are listed in Table 4 by their terminal name in CLOUSE & al. (2015). A sample of some of the variation in head shape of major workers from across Micronesia is shown in Figures 27 ­ 29.

Tab. 4: Camponotus micronesicus sp. n. types and closely related specimens from Melanesia. Specimens are identified by their terminal name in CLOUSE & al. (2015), followed by original collection codes.

Federated States of Micronesia: Chuuk, Tol  Island at 120 m (7º 19' 27.3" N, 151º 36' 50.6" E), 8.IX.2010, leg. R. Clouse, P. Sharma, and Techuo family
Federated States of Micronesia: Chuuk, Tol  Island at 120 m (7º 19' 27.3" N, 151º 36' 50.6" E), 8.IX.2010, leg. R. Clouse, P. Sharma, and Techuo family
Federated States of Micronesia: Chuuk, Tol  Island at 120 m (7º 19' 27.3" N, 151º 36' 50.6" E), 8.IX.2010, leg. R. Clouse, P. Sharma, and Techuo family
Paratype major and minor, PAL.1.CAM.Ngarchelong, 52761 & JCM0148a