The Ants of Africa
Genus Crematogaster - Subgenus Decacrema
Genus Crematogaster Introduction

Subgenus Decacrema Forel (1910f: 9)

Diagnostic Features - The only subgenus with 10-segmented antennae. Forel's (1910f) subgenus definition is at {original description}.


These can be divided into two distinct species groups.
1. The hova-group of relatively large, TL at least 3.0 mm, sculptured dark species. The Madagascar species Crematogaster (Decacrema) hova Forel (1887: 387) can be seen at http://www.antweb.org/description.do?rank=species&genus=crematogaster&name=hova&project=.
2. The solenopsides-group of small, TL no more than 2.0 mm, almost unsculptured, smooth, shiny, essentially pale species.


Note: Blaimer, Bonnie B., 2010. Taxonomy and Natural History of the Crematogaster (Decacrema)-group (Hymenoptera: Formicidae) in Madagascar. Zootaxa, 2714, 1-39 (available on line as free access).

She listed C. arthurimuelleri Forel, C. edentula Santschi, C. lango Weber, C. liengmei Forel (incl. 2 subspecies), C. petiolidens Forel and C. solenopsides Emery (incl. 3 subspecies) from Sub–Saharan Africa. and observed "The morphology of all but one examined African species further refutes a close relationship to the Decacrema of Madagascar (Blaimer, pers. observ.) and warrants further study".

Blaimer's key to Malagasy species separates into two groups; the first with the petiole with potero-lateral tubercles and paired coarse erect hairs on both petiole and postpetiole; the second without an angular petiole and usually with the erect hairs.  My key predates hers but the same separation applied to African species matches my couplet 2 with her second group; and my couplet 3-onwards with her first group.

She listed liengmei as among those she examined and my specimens show the similarity to the Malagasy species she recognised. Further, it seems likely the true Decacrema are of second group, which includes the genus type-species, C, schencki. Thus, at some future point the first group of African species might merit placement in a separate subgenus.


Key to species - workers


1 Antenna with scapes reaching the occiput, funiculus with a 3-segmented club; head and alitrunk with distinct sculpturation giving those parts a semi-matt appearance; base colour dark-brown to black; TL at least 3.0 mm 2
-- Antennal scapes reaching no more than the 3/4 point of the head, club 2-segmented; with reduced sculpturation, so generally smooth and shiny; base colour no more than yellow-brown; TL no more than 2.5 mm 3
2
TL 3.0-3.7 mm; antenna with scapes reaching the occiput, funiculus with a 3-segmented club; petiole without an anterior subventral tooth, only an obtuse protuberance; propodeal spines relatively long & sharp; head submatt and finely sculptured; alitrunk with quite strong sculpturation; black, appendages dark brown or blackish-brown
.
. {Crematogaster liengmei} Southern Africa - liengmei
-- Propodeum without teeth 3
3 Crematogaster edentulaPropodeum without teeth; TL 2.0-2.5 mm; shiny, colour light rust-brown, antennae and legs yellowish, Guinea - edentula
-- Propodeum with at least small denticles 4
4 {Crematogaster lango}Petiole with only a small anterior subventral tooth; TL only 1.9 mm; propodeal teeth triangular and flat; overall shiny; few erect hairs; bright brown, appendages more yellow .
. {Crematogaster lango} Sudan - lango
-- Petiole with a long anterior subventral tooth 5
5 {Crematogaster petiolidens}TL 1.6-2.0 mm; head rectangular about one-fifth longer than wide; eyes small with no more than 12 facets; propodeal spines short andt triangular with a wide base, height equal to base; petiole square with teeth at each angle, the anterior pair small but the posterior pair very distinct; subpetiolar anterior tooth not mentioned; rust or reddish with head and gaster brown West Africa & Congo Basin - petiolidens
-- Eyes larger 6
6 {Crematogaster costeboriensis}TL 2.0 mm; head slightly longer than wide, laterally convex; eyes flat; promesonotum convex; propodeal spines a little longer than one-third their basal separation; propodeum laterally bordered; lateral mesonotum and propodeum distinctly but finely punctate; petiole trapezoidal, with the anterior and posterior angles dentate, subtended by an almost horizontal tooth; dark brown, gaster brown-black, appendages brownish-red; characterised by quite abundant and moderately long erect hairs on head and alitrunk
West Africa - costeboriensis
-- {Crematogaster solenopsides}TL 2.5 mm; head slightly longer than wide; eyes large, set at midpoint of head; alitrunk convex; no pubescence, very few erect hairs; shiny clear brown colour, anterior of head and gaster darker Pan-African - solenopsides

Crematogaster (Decacrema) species 563

Listed by Room (1971) from cocoa canopy and mistletoe at the Mamfe-Mampong cocoa farm in Ghana. This may be the species referred to but not named in any way by Strickland (1951a), as being taken eight times in association with mealybugs on cocoa at CRIG. It is possible that this is C. costeboriensis (see above).

Contents MYRMICINAE Introduction
2007, 2008, 2010, 2012, 2014, 2015 - Brian Taylor CBiol FSB FRES
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