Key to Iberian Peninsula Messor species

This key is based on specimens and modified from the one created by Xavier Espadaler and Kiko Gómez for www.hormigas.org

In the Iberian Messor species exists a continuus degree of polimorphism. A group of species (Messor celiae, Messor hispanicus, Messor lobicornis) can be named as monomorphic, as the size of the workers is quite similar to the variation know in Messor. Another group (Messor barbarus, Messor bouvieri, Messor capitatus, Messor marocanus, Messor structor, Messor timidus) is clearly polimorphic. But, as usually happens in Nature when we're trying to dicotomyze reality, there's one species (Messor lusitanicus) with a polmorphism in the middle of these two groups. The degree of polimorphism is a valid characteristic in species diferentiation for some pair of species.

In order to achieve a reliable identification it is advisable to use workers of all sizes, specially majors.

1

 * Scape strongly swollen at its base, forming a rounded lobe at the proximal zone of the scape. Colour black. Whole body dull. Propodeum angulose, sometimes forming spines. Monomorphic ..... Messor lobicornis


 * Scape cylindrical, getting thinner to the base. If a lobe exists (Group structor), this is conspicuous and starts at the base of the scape, continuing the scape profile in a more or less triangular lobe. Monomorphic or polimorphic. Propodeum with various shapes..........2

2
return to couplet .....1
 * Psammophorus (long "J" shaped hairs forming a basket) present on the gula.....5


 * Gula and mandibles with numerous uneven quetae, and not forming a basket. The whole body covered with erect to decumbent pilosity.....3

3
return to couplet .....2


 * Clypeus emarginated (except in the minor workers, which clypeus is very similar to barbarus group). Head with small erect quetae in frontal view, all over its perimeter. Rugose sculpture well developed .....Messor structor


 * Clypeus denticulated in its anterior margin. The head in frontal view can have erect quetae in the occipital border of the head, but without them on the genae. Sculpture weakler, specially on the head, which can be smooth in its majority .....4

4
return to couplet .....3


 * Propodeum rounded in profile view; major workers reaching 11 mm. and have the head with a reddish tinge, and rest of the body black. Minor workers with the whole body black .....Messor barbarus


 * Propodeum from angulose to bituberculated in profile view; colour black in all of the castes. Some major workers can present small spines on the propodeum .....Messor capitatus

5
return to couplet .....2


 * Propodeum rounded to angulose without clearly shaped spines .....6


 * Propodeum with clearly shaped spines .....Messor lusitanicus

6
return to couplet .....5


 * Unicoloured, brown to black .....7
 * Bicoloured head and gaster brown to black and mesosoma reddish .....Messor marocanus

7
return to couplet .....6


 * First gastral segment without hairs, or, exceptionally in some majors with a maximum of six hairs. Postpetiole profile semispheric .....Messor bouvieri


 * First gastral segment with hairs. Exceptionally in some minima workers of M. timidus can have a bald appeareance. Postpetiole profile otherwise .....8

8
return to couplet .....7


 * Scape with semierect to erect quetae.....Messor celiae


 * Quetae running parallel to the scape .....9

9
return to couplet .....8

Petiolar and pospetiolar nodes higher, almost in scale in the major workers. Body hairier, propodeum with several quetae in the upper surface


 * Petiole and postpetiole high, with more or less rounded profile, with a smooth transition between anterior and posterior faces. Monomorphic


 * Petiolar and pospetiolar nodes in triangular shape, not elevated, with a clearly demarcated angle between anterior and posterior faces. .....Messor timidus