Heterostylum

Distinguished from similar bee-fly genera by the combination of an indentation in the hind margin of the eye and unique wing venation patterns. The robust, very hairy body and 10–15 mm size are supportive characters. Species-level identification requires examination of coloration patterns and geographic distribution.

Associated with habitats supporting mining bee populations. Heterostylum ferrugineum has been documented in xerophilic forest habitats. Species distribution spans diverse environments from xeric regions of the southwestern United States to tropical forests of Central and South America.

Distributed throughout the Americas. Nearctic records include the western and central United States (Arizona, California, Colorado, Kansas, Missouri, New Mexico, Oklahoma, Oregon, Texas, Utah, Wyoming, Idaho, Nevada, Georgia) and Canada (Alberta), plus northern Mexico. Neotropical distribution includes Mexico (Baja California, Sinaloa, Sonora, Tamaulipas, Zacatecas, Guerrero, Morelos, Puebla, Coahuila, Tabasco), Cuba, Haiti, U.S. Virgin Islands, and South America (Argentina, Bolivia, Brazil, Colombia, Paraguay, Venezuela, Peru, Guyana, Guatemala). First recorded in the Lesser Antilles (Martinique, Guadeloupe, Saint-Barthélemy) in 2005.

Larvae are parasitoids that feed on the larvae of mining bees (Andrenidae). Adult feeding habits are not documented in available sources.

• Nomia melanderi (alkali bee) - parasitoidHeterostylum robustum specifically parasitizes this solitary bee species.
• Mining bees (Andrenidae) - parasitoidLarvae of the genus feed on mining bee larvae; specific host associations beyond H. robustum are not documented.

Parasitoid life cycle: females deposit eggs near host bee nesting sites; larvae enter host cells and develop within the bodies of developing bee larvae; pupation occurs after consuming the host. Specific details on egg, larval instars, and pupal duration are not available from provided sources.

Adult females exhibit egg-laying behavior adapted to locate and exploit aggregations of solitary bee nests. The parasitic strategy involves depositing eggs near host nesting sites rather than direct host contact.

Acts as a parasitoid of solitary mining bees, potentially regulating bee populations. Heterostylum robustum parasitizes the alkali bee, an important pollinator of alfalfa, suggesting potential impact on agricultural pollination services through host population suppression.

Heterostylum robustum may impact alfalfa pollination by parasitizing the alkali bee, a managed pollinator for this crop. No other direct human interactions are documented.

• Other Bombyliidae generaLack the diagnostic indentation in the hind eye margin and unique wing venation characteristic of Heterostylum.
• Bees (Hymenoptera: Apoidea)Convergent hairy appearance, but distinguished by single pair of wings (Diptera), eye structure, and wing venation.

• parasitoid
• bee-fly
• mining bee parasite
• solitary bee parasite
• alkali bee parasite
• Americas distribution
• Bombyliidae
• Diptera

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• Catalogue of Life
• The Biology of Heterostylum Robustum (Diptera: Bombyliidae), A Parasite of the Alkali Bee1
• First record of the genus Heterostylum Macquart, 1848, in the Lesser Antilles (Diptera, Bombyliidae)