Potential new evidences of bee fly parasitoidism on ground-dwelling insects in mid-Cretaceous Burmese amber (Diptera: Bombyliidae)

Two new 'Tomophthalmae' bee flies Paleocytherea pouilloni gen. et sp. nov., and Nidergasia neraudeaui gen. et sp. nov. are described from the mid-Cretaceous Burmese amber. They are provisionally not attributed to a precise subfamily. The female of Paleocytherea pouilloni has terminalia modified into a very wide chamber with acanthophorite spines on tergites 9 + 10 and a row of ventral setae evocating a specialized hair brush. These structures allowed digging into sand to lay eggs, and possibly would characterize a sand chamber similar to those of several extant Bombyliidae that use it to coat eggs with sand and attack ground-dwelling insects. Eggs are wrapped with sand, avoiding dessication and/or direct competition with more efficient parasitoids, including wasps. This discovery suggests a potential great antiquity for this behavior (e.g., potential competitors like angarosphecid wasps are recorded in Burmese amber). Potential bee fly hosts were antlions, pygmy mole crickets, and the earliest bees, also known in the Burmese amber.