Pterallastes
Loew, 1863
Species Guides
1- Pterallastes thoracicus(goldenback fly)
Pterallastes is a of -mimicking hoverflies ( Syrphidae) described by Loew in 1863. The genus contains four recognized with a disjunct distribution: one species in North America (P. thoracicus), one in Japan (P. unicolor), and two in China (P. bomboides, P. bettyae). These flies exhibit of bees, a common defensive strategy in the Eristalinae.
Pronunciation
How to pronounce Pterallastes: //tɛrˈæləstiːz//
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Identification
Members of this can be distinguished from other -mimicking syrphids by their robust body form and specific wing venation patterns characteristic of the tribe Milesiini. Pterallastes thoracicus, the North American , has an orange that provides the 'Orangeback syrphid fly.' The genus is distinguished from similar bee-mimicking hoverfly genera such as Mallota and Arctophila by subtle morphological features of the and leg structure, though precise identification requires examination of diagnostic characters.
Images
Distribution
Disjunct distribution across three regions: North America (P. thoracicus, ranging from the United States to southern Canada with recent range expansion documented), Japan (P. unicolor), and China (P. bomboides and P. bettyae from Sichuan province).
Behavior
have been observed visiting flowers. The North American P. thoracicus engages in pollinating at flowers, based on photographic records from citizen science platforms.
Ecological Role
function as through their flower-visiting . The -mimicking appearance suggests a defensive against .
Human Relevance
Documented through citizen science initiatives such as iNaturalist and the City Nature Challenge, contributing to range expansion knowledge for P. thoracicus in North America. The serves as an example of disjunct biogeographic patterns in hoverfly evolution.
Similar Taxa
- MallotaBoth are -mimicking hoverflies in tribe Milesiini with robust body forms; distinguished by and leg .
- ArctophilaSimilar -mimicking appearance in Eristalinae; Pterallastes differs in specific structural features of the and .
- EristalisBoth are -mimicking syrphids, but Eristalis belongs to a different tribe (Eristalini) and typically shows more pronounced abdominal banding patterns.
More Details
Taxonomic Uncertainty in Species Count
Sources disagree on the number of in this . Wikipedia entries vary between two and four species, while the original sources indicate four described species. This discrepancy likely reflects ongoing taxonomic revisions or incomplete updating of different databases.
Range Expansion Documentation
P. thoracicus has shown recent northward range expansion into Canada, with new records from Ontario and Manitoba reported in 2024, plus a previously overlooked historical specimen. This expansion was documented using both museum specimens and citizen science observations from iNaturalist.