Key to Plectroctena Species

This key modifies Bolton & Brown (2002)^[1] to include Plectroctena thaui, described in Fisher (2006)^[2], covering all the described species for the genus

1

Propodeum with a continuous cuticular lamella that forms an uninterrupted projecting flange across the dorsum and down the sides of the declivity. Apical half of each mandible swollen, basal tooth always absent. Head relatively narrow. CI < 80 …..2
Propodeum either without a projecting cuticular lamella or with a lamella that is confined to each side of the declivity and does not extend across the dorsum. Apical half of each mandible not swollen, basal tooth usually present. Head relatively broad. CI > 85 …..3

2

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Dorsal surfaces of head, alitrunk, petiole and first and second gastral tergites with numerous short erect to suberect hairs. Eyes present, minute .....Plectroctena hastifera

Plectroctena hastifera

Dorsal surfaces of head, alitrunk, petiole and first and second gastral tergites without standing hairs of any form. Eyes absent .....Plectroctena anops

Plectroctena anops

3

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Dorsum of first gastral tergite with an anteriorly located transverse groove or impression which may extend the width of the tergite or be confined to the median quarter of the width of the sclerite …..4
Dorsum of first gastral tergite without trace of an anteriorly located transverse groove or impression …..7

4

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Ventral surfaces of the head and usually also the sides of the head, at least below and behind the eyes, with the spaces between punctures finely striate. Funicular segments 3-4 as long as, or longer than broad …..5
Ventral surfaces of the head and the sides of the head below and behind the eyes with the spaces between punctures smooth and shining. Funicular segments 3-4 broader than long, usually markedly so …..6

5

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Very large species with relatively very long mandibles. HL > 4.0. MI > 90. Transverse groove on first gastral tergite strongly developed across the width and preceded by a thick crest of cuticle, very conspicuous in profile .....Plectroctena cristata

Plectroctena cristata

Smaller species with relatively shorter mandibles. HL < 4.0. MI < 90. Transverse groove on first gastral tergite faint and poorly developed, only visible in the middle of the tergite and not preceded by a thick crest of cuticle, scarcely discernible in profile .....Plectroctena dentata

Plectroctena dentata

6

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Petiole node in dorsal view as broad as long .....Plectroctena latinodis

Plectroctena latinodis

Petiole node in dorsal view longer than broad .....Plectroctena minor

Plectroctena minor

7

return to couplet #3

Dorsum of head coarsely sculptured with foveolae or large pits whose diameters are greater than the distances that separate them or which are adjacent. Mesonotum and propodeum with a polished, virtually unsculptured, median longitudinal strip .....Plectroctena cryptica

Plectroctena cryptica

Dorsum of head finely sculptured with small punctures whose diameters are less than the distances that separate them. Mesonotum and propodeum without a polished, virtually unsculptured, median longitudinal strip …..8

8

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Labrum shallowly transversely concave and with a sharply incised median longitudinal groove that extends the entire length of the sclerite and completely breaks the fine surface sculpture. Mandible edentate .....Plectroctena macgeei

Plectroctena macgeei

Labrum without a median longitudinal groove, the line surface sculpture uninterrupted across the entire shallowly transversely concave sclerite. Mandible at least with a strong basal tooth, usually also with a second, smaller, tooth in the apical half …..9

9

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Dorsal surfaces of head and alitrunk with numerous short erect or suberect hairs present .....Plectroctena gestroi

Plectroctena gestroi

Dorsal surfaces or head and alitrunk without standing hairs …..10

10

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Ventral surfaces of head without striation between the punctures …..11
Ventral surfaces of head with striation between the punctures, at least anteriorly …..14

11

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Propodeal declivity armed near its base with a stout triangular tooth; lamella not developed dorsal to the tooth. Larger species. HL > 3.0; full adult colour blackish brown to black .....Plectroctena laevior

Plectroctena laevior

Propodeal declivity not armed near its base with a stout triangular tooth; lamella fully developed and extends almost the height of the declivity. Smaller species HL < 2.5; full adult colour orange-brown or dark red …..12

12

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Foveolate punctures on dorsum of head each with an appressed small hair arising from its centre, the hair directed toward the cephalic midline .....Plectroctena lygaria

Plectroctena lygaria

Foveolate punctures on dorsum of head without appressed small hairs arising from their centres …..13

13

return to couplet #11

Basal tooth on mandible with distal (anterior) and proximal (posterior) surfaces that are of about equal length and slope; proximal base of tooth linked to mandible base by a shallow low ridge. Colour orange-brown .....Plectroctena subterranea

Plectroctena subterranea

Basal tooth on mandible with vertical distal (anterior) surface but without a defined proximal (posterior) surface; instead the apex of the tooth is extended to the mandible base as an oblique high ridge…..15

14

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Leading edge of scape with a row of suberect to erect short hairs. All dorsal surfaces of head and body entirely covered with extremely dense fine striate sculpture .....Plectroctena strigosa

Plectroctena strigosa

Leading edge of scape without suberect to erect short hairs. Sculpture variable in density and intensity but not all dorsal surfaces of head and body entirely covered with extremely dense line striate sculpture .....Plectroctena mandibularis