# Maroon-legged lion fly (Promachus hinei) > A medium-large predatory robber fly with distinctive dark maroon legs that hunts other insects in sunny, open habitats. Source: https://insectscanner.com/species/maroon-legged-lion-fly/ (updated 2026-10-10) ## Is it dangerous? **Can bite.** Not venomous to people in the manner of medically dangerous spiders or wasps, but adults have a strong piercing proboscis and can deliver a painful defensive bite if handled or trapped against the skin. Clean and treat bites as you would any puncture wound; seek medical attention if excessive pain, swelling or signs of infection occur. **Pets:** Generally not a threat to pets. A curious pet might be nipped if it tries to catch the fly, which could cause a brief painful bite but no lasting medical concern in most cases. ## Quick facts - Scientific name: Promachus hinei - Also called: Hine's bee-killer, Hine's robber fly - Order: Diptera (Flies) - Family: Asilidae (Robber flies) - Size: 20-35 mm body length - Colours: Maroon, Dark brown, Black, Grey (hairs) - Habitat: Sunny open habitats: fields, grasslands, roadsides, forest edges and disturbed areas where adults perch on vegetation or bare ground. - Range: North America: central and eastern United States, especially the Great Plains, Midwest and South. - Active: Warm months (spring to late summer); active during daylight, especially sunny hours. - Lifespan: Adults live for several weeks; full life cycle likely takes 1 year but specific timing is not well documented for this species. - Effect on plants: Harmless - Pest: no ## Overview Promachus hinei is a species of robber fly (family Asilidae). Like other robber flies it is a fast, aerial predator as an adult and captures a wide range of other insects in flight. Adults are usually active in warm months and are most often seen perching in open, sunny places from which they sally out to catch prey. Larvae are predatory and develop in soil or decaying organic matter. This species is part of the Promachus group of large, stout-bodied asilids and is recognized by its entirely reddish-brown legs, banded abdomen and robust, bristly appearance. It is not known to be of medical significance to people, though adults can deliver a painful bite if handled or trapped against skin. ## How to identify it Adults are large and robust for robber flies, with a broad brown thorax, a long tapered abdomen and a dense pale moustache of bristles (mystax) on the face. Legs are entirely reddish-brown to maroon and hairy. The abdomen is cream to pale with thick black cross-bands and a dark tip. Wings are clear to brownish and do not reach the tip of the abdomen at rest. The head has large dark compound eyes and a stout, piercing proboscis used to kill prey. - Notice the entirely reddish-brown to maroon legs — a distinguishing feature for this species. - Look for a large, robust fly with a bristly 'moustache' (mystax) on the face and a stout piercing proboscis. - Perches on stems, posts or bare ground in sunny, open areas and makes short sallies to catch flying insects. - Pale abdomen with thick black cross-bands and clear to brownish wings; large size (20-35 mm). ## Lookalikes - **Red-footed cannibalfly** (Promachus rufipes): Very similar in size and shape, but its legs are partly black (femora largely dark) rather than entirely reddish, and males have a white tuft near the abdomen tip. - **Other large robber flies** (Various Asilidae): Many asilids are similarly large and bristly; check leg colour, body proportions and local range to distinguish Promachus hinei. ## Life cycle - **Egg:** Laid in soil, leaf litter or decaying organic matter; specific oviposition habits for this species are not well documented. - **Larva:** Soil-dwelling predatory larvae that feed on other invertebrates in the substrate or rotting wood. - **Pupa:** Prepupal and pupal stages occur in the soil; development details are similar to other asilids but are not well-studied for this species. - **Adult:** Aerial predator that hunts insects in flight; adults mate and females lay eggs in suitable ground or litter habitats. ## Diet and predators - Young eat: Predatory: insect larvae and small soil invertebrates - Adults eat: Predatory: other insects captured in flight (beetles, bees, wasps, flies, and other flying arthropods) - Predators of the young: Ground predators such as beetles, ants and small mammals; parasitoids may also attack larvae though specific records are limited. - Predators of adults: Birds, spiders, larger predatory insects and insectivorous animals. ## Effect on plants and gardens Adults do not feed on plants; they are predators of other insects and therefore can help control pest species. Larvae develop in soil or decaying organic matter and do not harm live plants. ## Where and when to find it Adults: perched on stems, posts, bare ground or low vegetation in sunny open habitats. Larvae: in soil, sand or decaying organic matter. - Best time: Warm months (spring through late summer) during daytime, especially sunny midday hours. - Tips: Photograph from a distance with a telephoto or zoom — approach slowly and avoid quick movements. A macro lens from 1-2 m can capture details; try to show the legs and face (mystax) for identification. ## Fun facts - Robber flies are among the most effective aerial predators of insects — they catch prey on the wing and often return to the same perch. - The 'mystax' (facial bristles) helps protect the fly's head and eyes from thrashing prey. - Promachus species are also called 'bee-killers' because they regularly catch bees and wasps in flight. ## Frequently asked questions ### Are maroon-legged lion flies dangerous? Only mildly. They have no venom of concern to people, but an adult can deliver a painful bite if handled or trapped against skin. ### Do maroon-legged lion flies bite people? They generally do not bite people unless provoked or handled. Bites are defensive and uncommon. ### Why is this fly in my yard or on my house? Adults hunt flying insects and use sunny perches such as fences, posts and vegetation — yards with open sunny areas attract them because prey is abundant. ### How can I get rid of robber flies? Because they are useful predators, control is usually unnecessary. To discourage them, reduce open sunny perches and dense insect-attracting plantings near entrances. Avoid handling them; if an individual is unwanted indoors, gently guide it outside using a container and paper. ### Where does Promachus hinei live? It occurs in North America, typically in sunny open habitats such as fields, grasslands, roadsides and forest edges. --- More about this species: [iNaturalist](https://www.inaturalist.org/taxa/55773), [Wikipedia](https://en.wikipedia.org/wiki/Promachus_hinei). Identify insects and spiders from a photo with the Insect Scanner iPhone app: https://apps.apple.com/app/id1543946563?pt=126685406&ct=web-markdown&mt=8 Identification from photos is never certain: don't handle insects you can't identify, and get medical advice for bites, stings or allergic reactions.