Excerpt: Very little is known of the biology of bee-flies in the genus Geron; the few available records show that the larvae are parasitic on Lepidoptera larvae. Mik (1896) noted that Geron gibbosus Meigen had been reared from larvae of the pyralid Nephopteryx sublineatella Strg. and the psychid Fumaria crassiorella (Bruand) in Europe, while Maxwell-Lefroy and Howlett (1909) recorded the tortricid Laspeyresia jaculutrix Meyrick as a host of Geron argentifrons Bru. in India. The present paper appears to be the first report on the biology of any North American Geron.
Donahue, Julian P.
"Geron Calvus (Diptera: Bombyliidae), a Parasite of Solenobia Walshella (Lepidoptera: Psychidae) in Michigan,"
The Great Lakes Entomologist, vol 1
Available at: https://scholar.valpo.edu/tgle/vol1/iss8/5