Several eggs are laid in lepidopteran larvae and erupt to spin their cocoons when the caterpillar is in the final instar.

Those reported by Güçlü & Özbek[2] include: Conistra vaccinii, Jodia croceago, Lithophane ornitopus, Noctua fimbriata, Xanthia ocellaris, with additional records of host species Lasionycta proxima,[3] and Xylena vetusta.

[4] van Achterberg[5] gives a key for identification of Braconidae from Greenland that includes a description of M. mandibularis, which can be distinguished from related species by its colouration.

Fernandez-Triana et al.[6] report M. mandibularis from: Greenland, Armenia, Azerbaijan, Croatia, Finland, Georgia, Germany, Hungary, Macedonia, Mongolia, Netherlands, Russia (PRI, SAK), Serbia, Slovakia, Spain, Sweden, Switzerland, Tunisia, Turkey, United Kingdom.

It has additionally been recorded from Romania,[7] Iran,[8] and from Belgium and the Czech Republic.