Family: Pipunculidae
Subfamily: Nephrocerinae
Length: 6-12 mm
Until 2005, dipterologists believed that Big-headed Flies (family Pipunculidae) are all endoparasitoids of hoppers in the group Auchenorrhyncha. In that year, however, David Koenig and Chen Young at the Carnegie Museum of Natural History discovered that the hosts of a new species of Big-headed Fly in the genus Nephrocerus are Crane Flies (Tipula spp.) (Koening and Young, 2007.)
Koenig and Young’s article not only shed important light on the life history of this unusual genus of the Big-headed Flies, it was also the first recorded instance of a Crane Fly being parasitized by another Dipteran. The Nephrocerus larvae feed actively for less than twenty days, then enter diapause and do not pupate until ten months later. Koenig and Young found that 42% of female Crane Flies in their study area were parasitized by Nephrocerus but that only 0.008% of males were.
Skevington notes that Nephrocerus species look more like Syrphids than they look like other Pipunculids. If in doubt, check for the spurious vein found in Syrphids; Nephrocerus flies lack this vein. Other traits of Nephrocerus listed by Skevington include a kidney-shaped flagellum, the lack of a pterostigma, and huge eyes that are deeply notched along the center of their hind margins.
The fly shown here is a male; females have a modest separation between the eyes; in other words, female Nephrocerus are dichoptic.
