Belongs within: Euplectitae.
Melba is a North American genus of pselaphine beetles with a rounded prothorax (Raffray 1903).
Characters (Raffray 1903): Head large and truncated in front, with grooves and dimples. Antenna eleven-segmented; last segment very large and alone forming club. Palps with last article much larger than previous one. Prothorax sides rounded, without rim, transverse groove extending onto sides or ending in a more or less pronounced dimple, located on sides and invisible above. Elytra with rounded shoulders, not toothed, but well marked. Mesocoxae contiguous, processes of meso- and metasternum reduced to very thin blades hidden by coxae. Metacoxae contiguous. Abdomen with first tergite subequal to next. Posterior hips contiguous.
<==Melba Casey 1897 [incl. Zolium Casey 1897]R03
|--M. americana (Leconte 1863) [=Trimium americanum]R03
|--M. clypeata (Reitter 1883) [=Trimiopsis clypeata]R03
|--M. dentipes Raffray 1903R03
|--M. eggersi (Reitter 1882) [=Trimiopsis eggersi]R03
|--M. fleutiauxi (Raffray 1890) [=Trimiopsis fleutiauxi]R03
|--M. fossigerR03
|--M. gibbula (Reitter 1883) [=Trimiopsis gibbula]R03
|--M. gracilis (Brendel 1892) [=Trimium gracile]R03
|--M. grenadensis Raffray 1903R03
|--M. inconspicua (Reitter 1883) [=Trimiopsis inconspicua]R03
|--M. laticollis (Brendel 1892) [=Trimium laticolle]R03
|--M. major (Brendel 1892) [=Trimium major]R03
|--M. mimula [=Trimiopsis mimula]R03
|--M. minuta [=Trimiopsis minuta]R03
|--M. parmata (Reitter 1883) [=Trimiopsis parmata]R03
|--M. parvula (Leconte 1848) [=Euplectus parvulus, Trimium parvulum]R03
|--M. puncticollis (Leconte 1878) [=Trimium puncticolle]R03
|--M. quadrifoveata Raffray 1903R03
|--M. simplex (Leconte 1878) [=Trimium simplex]R03
|--M. specularis (Reitter 1883) [=Trimiopsis specularis]R03
|--M. sulcatula Casey 1897R03
|--M. texanaR03
|--M. thoracica (Brend. 1889) [=Trimium thoracicum]R03
|--M. uniformisR03
`--M. ventricosa (Reitter 1883) [=Trimiopsis ventricosa]R03
*Type species of generic name indicated
References
[R03] Raffray, A. 1903. Genera et catalogue des psélaphides. Annales de la Société Entomologique de France 72: 484–604.