Pantophthalmids are the bulkiest flies in the world; this female measured a whopping 3.5 cm. Although they bear resemblance to horse flies (Tabanidae), the two families are only distantly related. Pantophthalmids do not feed as adults. The larvae are borers in dead trees, although one species injures live oaks and is occasionally regarded as a pest.
Specimen contributed by M.D. Jackson.
iNaturalist observation