Probolomyrmex

Eguchi, K., Yoshimura, M. & Yamane, S., 2006, The Oriental species of the ant genus Probolomyrmex (Insecta: Hymenoptera: Formicidae: Proceratiinae)., Zootaxa 1376, pp. 1-35 : 33-34

[[ The Oriental species of the ant genus Probolomyrmex ]]

Discussion

Two species groups, the longinodus group and the greavesi group, can be recognized based on worker morphology among ten Oriental species and two Australian species that are dealt with or discussed in the present study. The longinodus group is characterized by the petiole which is clearly longer than high, and subpetiolar process which is low with poorly developed posteroventral portion. Probolomyrmex dammermani , P. itoi , P. longinodus , P. longiscapus , P. procne and P. watanabei are included here. They are separated from each other by SI, LPtI, development of propodeal spine, shape of posterodorsal portion of petiole, and/or shape of abdominal segment III in profile. The greavesi group is characterized by the petiole which is at most a little longer than high, and subpetiolar process which is developed and somewhat rectangular. Probolomyrmex bidens , P. greavesi , P. maryatiae , P. okinawensis , P. salomonis and P. vieti belong to this species group. Probolomyrmex bidens , in which the petiolar node has paired teeth posterodorsally, and P. okinawensis , in which the posteroventral portion of subpetiolar process forms an obtuse angle only, are relatively well distinguished from the other members of the greavesi group. On the other hand, P. greavesi , P. maryatiae , P. salomonis and P. vieti are only barely separated from each other based on worker morphology (see under P. maryatiae and P. vieti ). There are two possible views for this morphological similarity: they are geographical variants of a single variable species ranging from Indo-China to Australia and Solomon, or biological species with slight morphological differentiation. However, male morphology strongly supports the separation of P. greavesi from P. vieti at species level. Although more information is needed particularly for male characters of the other forms, we have inclined to the second view and described P. maryatiae and P. vieti as sibling species of P. salomonis and P. greavesi .

Male morphology supports the recognition of the two species groups. In the male of the longinodus group ( P. dammermani , P. longinodus and P. longiscapus ), the protrusion of the frontoclypeal region is relatively long, so that antennal insertion is situated in the middle of its dorsal surface; the third antennal segment is distinctly longer than the second; Mf1, Rs+M and media apical to Rs+M are present; cu-a cross vein is present; petiolar node is long and has a gentle anterior slope; median portion of the ninth abdominal sternum is strongly and roundly expanded apicad; genitalia are retractile. On the other hand, in the male of the greavesi group ( P vieti ), the protrusion of the frontoclypeal region is relatively short, so that antennal insertion is situated in apical portion of its dorsal surface; the third antennal segment is shorter than the second; Mf1, Rs+M and media apical to Rs+M are completely absent; cu-a cross vein is absent; petiolar node is very short and has a steep anterior slope; median portion of the ninth abdominal sternum is moderately expanded apicad and has an almost straight apical margin; genitalia are not retractile.