Key to the Species of Ischnomelissa

Females remain unknown for I. ecuadoriana, while males are unknown for I. rhina, I. cyanea, I. rasmusseni, and I. lignopteryx .

1. Females ......................................................................................................................... 2

―. Males ............................................................................................................................. 7

2(1). Malar space as long as or longer than basal width of mandible .......................... 3

―. Malar space shorter than basal width of mandible ............................................. 6

3(2). Head and mesosoma dark to metallic green with copper highlights .................. 4

―. Head and mesosoma dark metallic blue (Ecuador: Pichincha Province) .............. ............................................................................................. I. lescheni Brooks & Engel

4(3). Metasoma and legs dark brown except sometimes with some amber coloration basally on first metasomal tergum ............................................................... 5

―. Metasoma with first tergum and most of second tergum amber, remainder of metasoma brown, legs with tarsi, tibiae, and femoral apices amber, remainder of legs brown (Ecuador: Napo and Sucumbios Provinces) ... I. rhina Brooks & Engel

5(4). Metasomal terga entirely dark brown, with well-developed and distinct basal bands of yellow tomentum; wing membrane hyaline and clear; head and mesosoma distinctly dark metallic green and shining; inner metatibial spur with 17 branches, not including apical portion of rachis (Ecuador: Loja Province) ............................................................................. I. rasmusseni Engel & Brooks

―. Metasomal terga dark brown except basally amber on first tergum (Fig. 1), tergal graduli without bands of tomentum; wing membrane strongly infumate (Fig. 1); head and mesosoma dark green, not shining (Figs. 1–3); inner metatibial spur with 12 branches, not including apical portion of rachis (Peru: Amazonas Department) ........................................................... I. lignopteryx Engel, n. sp.

6(2). Integument of head and mesosoma dark metallic blue; T1–2 dark brown; inner metatibial spur with 12 branches, not including apical portion of rachis (Colombia: Nariño Department) ..................................... I. cyanea Brooks & Engel

―. Integument of head and mesosoma non-metallic, dark brown; T1 and most of T2 amber; inner metatibial spur with 15–20 branches, not including apical portion of rachis (Colombia: Huila and Valle del Cauca Departments) ... I. zonata Engel

7(1). Malar space almost as long as wide to slightly longer than wide ........................ 8

―. Malar space linear, much shorter than wide (Colombia: Huila and Valle del Cauca Departments) ........................................................................... I. zonata Engel

8(7). First flagellomere one-half length of second flagellomere; mandible, malar space, and scape at least anteriorly pale; malar space slightly shorter than wide (Ecuador: Pichincha Province) ................................... I. lescheni Brooks & Engel

―. First flagellomere one-fourth length of second flagellomere; mandible, malar space, and scape dark brown to black; malar space slightly longer than wide (Ecuador: Imbabura Province) .............................. I. ecuadoriana Brooks & Engel