Rhopalosyrphus guentherii (Lynch Arribalzaga)  

Rhopalosyrphus is defined (synapomorphy) by its 1) abdominal structure and 2) pilose meropleuron. Other diagnostic characters are 3) antenna elongate, longer than face, usually about twice as long; 4) scape and basoflagellomere elongate; 5) face produced ventrally; 6) occiput greatly developed on dorsal 1/3; 7) metasternum developed, not reduced; and 8) metatibia flared apically (Weems et al. 2003).

Rhopalosyrphus guentherii has 3rd tergum elongate, as long as the 2nd tergum; 2nd tergum not greatly elongate posteriorly; eye without enlarged ommatidia; alula bare basomedially; cell R completely bare behind spurious vein; metasternum with long, distinct pile, not reduced; and face and anepisternum entirely white pilose. R. ramulorum Weems & Deyrup differs by having alula completely microtrichose; cell R extensively microtrichose, bare only on basoposterior 1/4 or less; metasternum appearing bare, with pile greatly reduced; and face and anepisternum partially black pilose (Weems et al. 2003).