[1][2] It is known from northern Europe and North America,[3][4] and has been considered to be a rare species in parts of its range.

[19] Thus, P. nigritarsus is considered to be present throughout the Northern Hemisphere and it is one of several syrphid species included in the 'Barcode of Life Data System,[20] a project focusing on species occurring in Canada that includes taxonomic information, metadata, and DNA sequences for several individuals at the mitochondrial cytochrome oxidase gene.

Consult DipteraMorphology page for definitions of specialized terms describing adult fly morphology.

[25][26][27][28] Parasyrphus nigritarsus has been implicated as a major natural enemy of leaf beetles in the subfamily Chrysomelinae within the Chrysomelidae.

[16] These leaf beetles lay multiple clutches of 10-30 eggs on host plants in early summer.

All beetle species that have been documented as prey to P. nigritarsus or its North American relative Parasyrphus melanderi possess external defensive secretion glands as larvae, from which they evert volatile secretions that are presumed to be repellent to potential predators.

[10][5] At the population level, these specialist predators are considered voracious and have significant impacts on beetle mortality.

[34] Other investigators of beetle population dynamics have noted the presence of a syrphid with very similar behaviors feeding on dock beetles Gastrophysa viridula in the United Kingdom,[35] and similar behaviors have been observed for Parasyrphus melanderi feeding on Chrysomela aeneicollis in California.