Obligate Predator

"Small slender robber flies are predatory on other tiny arthropods and insects, using rapid flight and ambush tactics. Despite their diminutive size, they employ the characteristic Asilidae predatory adaptations, such as piercing-sucking mouthparts with neurotoxic saliva. Their petite size does not compromise their predatory efficiency; instead, it suits them to specialized ecological niches among other small insects. They subdue prey with a piercing proboscis and venomous saliva, liquefying internal tissues before feeding"
bugswithmike.com & Wikipedia