Speiseria ambigua Kessel, 1925. Wenzel, Tipton, and Kiewlicz, 1966: 549-551, fig. 102; Wenzel, 1976: 125-127, fig. 50.
Specimens examined: La Selva: 4m 4f from Carollia brevicauda, 16m 3f 7 (sex undet.) from Carollia castaneae, 4m 1f 8 (sex undet.) from Carollia perspicillata, 21m 12f 2 (sex undet.) from Glossophaga comissarisi, 3m 1f from Lonchophylla robusta, 1f from Myotis sp. (dubious record?); El Gavilán: 1 (sex undet.) from Carollia brevicauda, 1 (sex undet.) from Carollia perspicillata.
Additional records: Braulio Carrillo: 1m from Lonchorhina aurita; La Selva or Braulio Carrillo: 1f from Carollia brevicauda, 1f from Carollia perspicillata (Timm et. al, 1989); La Selva: 12m 17f from Carollia perspicillata (Fritz, 1983).
Note: Wenzel (1976) postulated the existence, at least in Venezuela, of two almost cryptic species of Speiseria: S. ambigua and S. peytonae, distinguished by the curvature of the male genitalia, host preference, and unspecifically by degree of hairiness. Of the flies Wenzel identified as S. ambigua, 96% were collected from Carollia perspicillata while all the flies he identified as S. peytonae were collected from Carrollia brevicauda. I have observed some variation in the shape of the male genitalia among Speiseria at La Selva, but the differences are subtle and possibly continuous. Also, I have failed to find any specific correlating characters including host preference or chaetotaxic characters that might assist in diagnosing cryptic species within Speiseria. I therefore consider all Speiseria from La Selva that I have seen to belong to a single species. I do not rule out the possibility that more detailed work, perhaps involving genitalic dissection, may discover reliable diagnostic characters for species within this group.