Key to the species of Megascogaster

1. Ratio of length of fore wing to length of body 0.67; occipital carina complete (Fig. 2 b); propodeal tubercules absent (Fig. 1); mesopleuron shiny and punctate (Fig. 2 c); legs orange to light brown; female with 30 antennomeres (Philippines)........................................................................................... M. elongata Baker 1926

- Ratio of length of fore wing to length of body 0.75; occipital carina dorsally interrupted (Fig. 4 a); propodeal tubercules present (Fig. 3); mesopleuron shiny and smooth (Fig. 3); legs brown to dark brown (Fig. 3); female with 28 antennomeres (Sulawesi, Indonesia)............................................................................. M. wallacei sp. n.