Overbeckia Viehmeyer, 1916
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publication ID |
https://doi.org/ 10.1071/is21067 |
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DOI |
https://doi.org/10.5281/zenodo.6987098 |
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persistent identifier |
https://treatment.plazi.org/id/03E5E915-6518-0530-FF5B-F9279B2C2CE1 |
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treatment provided by |
Felipe |
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scientific name |
Overbeckia Viehmeyer |
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Genus Overbeckia Viehmeyer View in CoL
( Fig. 1 – 6 View Fig View Fig View Fig View Fig View Fig View Fig )
The diagnosis based on workers (for males and queens, see descriptions).
External morphology
Body length. 4–5 mm (min. to max. WL = 1.24–2.02, WL mean = 1.68 mm). No dimorphism or apparent polymorphism in workers.
Head. 12-segmented antennae including scape, without distinct club but with funicular segments continuously enlarged towards the tip, with distal flagellomere approximately twice as wide as the basal flagellomere ( Fig. 2 h View Fig ); scape curved and widened apically ( Fig. 1 b View Fig , 2 h View Fig ). Antennal socket relatively closer to the posterior margin of clypeus than in other Camponotini . Palp formula 6: 4, with apical segment of maxillary palp 15–20% shorter than the subapical segment ( Fig. 5 a View Fig ). Head in frontal view oval, with HL similar to HW (min. to max. CI = 94–105, CI mean = 101) ( Fig. 1 b View Fig ). Clypeus slightly convex anteriorly and posterior clypeal margin incised in the middle by a developed suture, forming the frontal triangle; but the posterior suture of the triangle below carinae not developed, rather only outlined by bent cuticle ( Fig. 1 d View Fig ). Frontal carinae well developed, going from clypeal margin up to the middle of the head ( Fig. 1 d View Fig ) and forming a convex lifted ridge between each carina and the antennal socket apparent at lateral view ( Fig. 1 a View Fig ); vertical groove in the middle of frons between carinae missing ( Fig. 1 d View Fig ) or only outlined by a glossy smooth line ( Fig. 5 d View Fig ). Mandibles triangular with five teeth that decrease in size from apical to basal teeth. Eyes relatively large (min. to max. EL = 0.25–0.40 mm, mean EL = 0.32) and placed vertically in the middle of the head, surpassing the head margins in frontal view, with ~20 ommatidia in the longest axis ( Fig. 1 b View Fig ). Workers without ocelli.
Mesosoma. Mesosoma shape resembles that of the genus Calomyrmex , with a well developed promesonotal suture. Metanotal groove limited at most of the length to the dorsum of thorax and ending laterally next to the metathoracic spiracle, with a depression and smooth area around the spiracle ( Fig. 1 a View Fig ). The depression next to metathoracic spiracle region is also well visible in dorsal view, with propodeum laterally constricted compared to relatively broad pronotum ( Fig. 1 c View Fig ).
Metasoma. Petiole squamiform and triangular, with sharp apex in lateral view and of relatively broad lentil-shape in dorsal view ( Fig. 1 c View Fig ); a characteristic subpetiolar process present and divided from petiole node by a ridge ( Fig. 1 a, c View Fig ). Petiolar and propodeal spiracle with light-coloured margins. Metapleural gland vestigial, probably not functional according to Heterick (2019).
Sculpture. On whole body, cuticle relatively smooth and glossy, with only fine punctation or soft lineation. No spines on thorax and petiole, and no deep wrinkles and pits present.
Pilosity. Rather short, appressed pilosity; a few longer erect hairs present however at least at the scape apex, on ventral head, abdomen and clypeus (hair length ≤ EL); in contrast to Calomyrmex lacking a dense cover of long, erect hairs over thorax and legs.
Colouration. Head, mesosoma and petiole dark brown to blackish colour, abdomen and appendages rather lighter (brown to light brown) and with yellowish coxae and trochanters; except frontal coxa that are darker, similar in colour to thorax ( Fig. 1 a View Fig , 2 g View Fig , 4 a View Fig , 5 a View Fig ).
Internal morphology: proventriculus in Overbeckia v. other Camponotini genera
Viehmeyer (1916) provided a drawing of the proventriculus in the original genus description, in which rather short sepals were described, being slightly bent anteriorly and of a similar length to the vertical length of the valve (i.e. ‘the stomach pump’), resembling in this respect the genus Paraparatrechina . These short sepals have been noted as a main feature to distinguish Overbeckia from other SE Asian Formicinae genera ( Bolton 1994). Our dissection conforms to the original drawing of Overbeckia ’s proventriculus by Viehmeyer (1916), showing a similar proportion of sepals compared to the valve. Furthermore, we observed that the valve has relatively thicker walls of whitish colour in Overbeckia , when compared to the other examined genera ( Fig. 3 a View Fig ). Our dissections of Echinopla also show sepals not much longer than the valve ( Fig. 3 c View Fig ), resembling the proventriculus of Overbeckia , but with softer and thinner walls (brittle structure). In contrast to Overbeckia and Echinopla , Calomyrmex has sepals approximately twice as long as the valve, similar to Opisthopsis (i.e. ‘ Formica ’ type in Eisner 1957; Fig. 3 b View Fig ). Colobopsis resembles Camponotus in the long sepals, more than 2.5× longer than the valve (i.e. ‘ Camponotus ’ type that also occurs in Polyrhachis ( Eisner 1957; Fig. 3 d View Fig ).
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