A new species of leaf-cutter bee, Megachile (Eutricharaea) arachosiana, new species, is described and illustrated based on males and females from west-central and northern Pakistan. The opportunity is taken to provide new taxonomic notes on the subgenus Eutricharaea Thomson. The subgenus Platysta Pasteels, comprising the large African species M. platystoma Pasteels and M. khamana Cockerell, is synonymized with Eutricharaea (new synonymy). It is noted that M. microxanthops Cockerell, considered widely a synonym of M. concinna Smith, is allied to M. apostolica Cockerell and is removed from synonymy accordingly. A new taxonomic summary is provided for M. concinna with M. microxantha Cockerell, M. atratula Rebmann, and M. privigna Rebmann considered new junior subjective synonyms (new synonymies).