Key to Crematogaster borneensis group workers

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This worker key is based on: Feldhaar, H., Maschwitz, U., Fiala, B. 2016. Taxonomic revision of the obligate plant-ants of the genus Crematogaster Lund (Hymenoptera: Formicidae: Myrmicinae), associated with Macaranga Thouars (Euphorbiaceae) on Borneo and the Malay Peninsula. Sociobiology. 63: 651-681.

Species identification of Macaranga-associated Crematogaster (Crematogaster borneensis-group) is easier and more conclusive based on queens as they possess more distinct characters than workers (i.e. length of compound eyes and the ocelli).

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1

  • Propodeal spines present, sometimes only short but always protruding beyond the posterior margin of the propodeal spiracle (see Supplementary S1.2C for long propodeal spines; S1.3C for short propodeal spines, Fig S2.4A and S2.4B;) . . . . . 2
  • Propodeal spines absent. Propodeum only slightly and bulb-like elevated above the propodeal spiracle (see Fig S1.5C and Fig S1.6C). . . . . . 7

2

return to couplet #1

  • Scape relatively short in relation to head width. Scape index (SI) < 0.65 . . . . . 3
  • Scape relatively long in relation to head width. Scape index (SI) > 0.65 . . . . . 5

3

return to couplet #2

  • Petiole always distinctly wider than postpetiole with PI > 1.15. Propodeal spines very short only with tip of spine barely protruding beyond margin of propodeal spiracle (Fig S1.7C and S1.7D). Species endemic to Borneo, mainly found in Sabah, occurring mostly on non-waxy host plants of the section Pachystemon (M. angulata, M. indistincta) and on the slightly wax covered M. glandibracteolata . . . . . Crematogaster claudiae
  • Petiole wider than postpetiole with PI ranging from 1.0 to 1.15, but PI rarely >1.10. Propodeal spines either very short with tip of spine barely protruding beyond margin of propodeal spiracle or distinctly longer. . . . . . 4

4

return to couplet #3

  • Legs in comparison to alitrunk length relatively short (RLEG between 0.58 and 0.62). Head usually as wide as long (CI around 1.0). Propodeal spines present but short, with the tip barely protruding beyond the posterior margin of the propodeal spiracle (LPS/WL ranging from 0.09 to 0.12) (see Supplementary Fig S2.4A and S2.4B; Fig S1.3C and S1.3D). Specimens from Peninsula Malaysia always have CI > 1.0, whereas specimens from Sarawak have more slender heads with CI ≤ 1.0. Species colonizes non-waxy hosts of the section Pachystemon (M. bancana, M. hullettii, M. kingii, M. trachyphylla, M. umbrosa); on Peninsula Malaysia found at higher elevation only (approximately > 500m). . . . . . Crematogaster hullettii
  • Legs in comparison to alitrunk relatively longer (RLEG between 0.61 and 0.69). Propodeal spines always prominent and acute, with the tip of the spine distinctly exceeding the posterior margin of the propodeal spiracle (LPS/WL ranging from 0.12 to 0.17). Head always longer than wide (CI < 0.98) (Fig S1.4C and S1.4D). Widespread on non-waxy host species of the section Pachystemon (M. angulata, M. bancana, M. calcicola, M. hullettii, M. indistincta, M. kingii, M. trachyphylla, M. petanostyla) . . . . . Crematogaster captiosa

5

return to couplet #2

  • Propodeal spines very short only, with the tip barely exceeding the posterior margin of the propodeal spiracle (LPS/WL ranging from 0.07 to 0.08). RLEG 0.67-0.72. CI > 0.94 (Fig S1.6C and Fig S1.6D). Species found on Borneo (Sabah, Sarawak, East Kalimantan), mostly on waxy host plants of the section Pachystemon (M. havilandii, M. hypoleuca, M. motleyana) and rarely on the non-waxy M. indistincta and M. angulata (in primary forest or at higher elevation). . . . . . Crematogaster maryatii
  • Propodeal spines long and acute (LPS/WL ranging from 0.1 to 0.17). . . . . . 6

6

return to couplet #5

  • CI ranges from 0.92 to 0.97, but most workers have a CI < 0.95. RLEG ranges from 0.62 to 0.71 and RLEG is rarely > 0.7. Petiole always wider than postpetiole (PI > 1.0; ranging from 1.01 to 1.14) (Fig S1.1C and S1.1D; Fig S2.4A). Species colonizes a large variety of waxy hosts from both section Pachystemon as well as Pruinosae (main host species: M. griffithiana, M. motleyana, M. hypoleuca (on the latter mainly on large trees), and M. pearsonii, M. pruinosa, and M. hosei, respectively). . . . . . Crematogaster borneensis
  • CI ranges from 0.94 to 0.97, most workers have a CI > 0.95. Legs in comparison to alitrunk length relatively long (RLEG ranges from 0.68 to 0.79 and is rarely < 0.7) (Fig S1.2C and S1.2D). Petiole approximately as wide as postpetiole (PI ranging from 0.93 to 1.07 but rarely < 0.99). Species colonizes predominantly waxy hosts of the section Pruinosae (M. hosei, M. pearsonii, M. pruinosa). . . . . . Crematogaster linsenmairi

7

return to couplet #1

  • Legs and scape relatively short with RLEG < 0.69 and SI < 0.65. Petiole always distinctly wider than postpetiole with PI > 1.15. Propodeal spines absent (Fig S1.7C and S1.7D). Species endemic to Borneo, mainly found in Sabah, occurring mostly on non-waxy host plants of the section Pachystemon (M. angulata, M. indistincta) and on the slightly wax covered M. glandibracteolata . . . . . Crematogaster claudiae
  • Legs and scape relatively longer with RLEG > 0.65 (usually > 0.7) and SI > 0.7, rarely below. Petiole may be wider than postpetiole, but PI always < 1.1. . . . . . 8

8

return to couplet #7

  • Head distinctly longer than wide, CI: 0.91. Propodeal spines absent. Species endemic to east of Peninsula Malaysia. Legs in comparison to alitrunk length relatively short and colonizing waxy hosts of the section Pachystemon (M. constricta and M. hypoleuca) . . . . . Crematogaster roslihashimi
  • Head only slightly longer than wide (CI 0.94 to 1.02). . . . . . 9

9

return to couplet #8

  • Propodeal spines always absent, with a sometimes nodiform elevation above propodeal spiracle present (Fig S1.5C and Fig S1.5D). Postpetiole always wider than petiole, PI < 1.0. Petiole only slightly nodiform in dorsal view, rather elongate. Legs relatively long with RLEG 0.71 to 0.85. Widespread species occurring over the whole distributional range of the symbiosis that colonizes waxy hosts of the section Pachystemon (M. beccariana, M. havilandii and M. hypoleuca) . . . . . Crematogaster decamera
  • Propodeum with nodiform elevation above propodeal spiracle or with very short propodeal spines (Fig S1.6C and Fig S1.6D). Petiole nodiform in dorsal view and as wide as or slightly wider than postpetiole, PI ranging from 0.98 to 1.07, PI rarely < 1.0. RLEG ranging from 0.67 to 0.72, in most workers RLEG < 0.7. Endemic to host species found on Borneo (Sabah, Sarawak, East Kalimantan), mostly on waxy host plants of the section Pachystemon (see queen key above) . . . . . Crematogaster maryatii