Allograpta obliqua (common oblique syrphid fly)
What it is
A small hover fly (6–8.5 mm) with yellow cross-bands on the abdomen and two oblique yellow marks near the tip. Adults hover and visit flowers; larvae are classic aphid hunters. Widely distributed across most of the continental U.S. and into Canada and the Neotropics.
Ecological role
Larval predator: Eggs are laid right beside aphid colonies; larvae hunt aphids (and sometimes whiteflies, psyllids, mealybugs, mites, and even tiny caterpillars). In crops, heavy larval presence can cut aphid numbers dramatically (reported 70–100% reduction in some outbreaks).
Adult pollinator: Adults feed on nectar and pollen and are frequent visitors to open, shallow flowers—helping pollinate a wide range of natives.
Lifecycle (quick)
Holometabolous: egg → 3 larval instars → puparium → adult. Eggs hatch in ~2–8 days; larvae feed 1–3 weeks; pupation occurs on plants or in litter/soil; adults emerge in ~1–2 weeks (unless the pupa overwinters). Multiple generations per season; adults present much of the growing season in the Midwest. Overwintering is species-dependent among syrphids but often as mature larvae or pupae in leaf litter/soil.
How to support it in a native garden (Chicago ecoregion)
Think in two tracks: (1) nectar/pollen for adults and (2) “prey base” plants that host aphids for the larvae.
1) Nectar & pollen—plant many shallow, long-blooming natives
Hover flies key in on umbels, daisies, and mints. Great, locally native picks that bloom in sequence:
Spring–early summer: golden alexanders (Zizia aurea), heart-leaved alexanders (Zizia aptera), prairie parsley (Polytaenia nuttallii).
Summer: mountain mints (Pycnanthemum virginianum, P. tenuifolium), wild bergamot (Monarda fistulosa), purple coneflower (Echinacea purpurea), black-eyed Susan (Rudbeckia hirta), Culver’s root (Veronicastrum virginicum).
Late summer–fall (critical for multiple generations): asters (Symphyotrichum spp.), goldenrods (Solidago spp.), joe-pye weeds (Eutrochium spp.), blazingstars (Liatris spp.).
(Adults “visit a variety of flowers,” especially open-centred ones; syrphid biology guides consistently note umbels/Asteraceae/Lamiaceae as prime resources.)
2) Build an aphid prey base (yes, some aphids are okay!)
Larvae need aphid colonies nearby. Don’t panic-spray; let a manageable aphid load exist on tough natives. Reliable aphid-hosting natives include: milkweeds (Asclepias spp.), native willows (Salix spp.), dogwoods (Cornus spp.), native cherries/plums (Prunus spp.), maples (Acer spp.), and viburnums (Viburnum spp.)—all plants that commonly support aphids without long-term harm and in turn feed syrphid larvae. (Females place eggs on leaves near aphids; larvae then patrol and feed.)
3) Habitat & maintenance tips
Leave leaf litter & some stems over winter so puparia/larvae can survive to spring.
Avoid broad-spectrum insecticides (even “organic” options like spinosad can disrupt syrphid control in veg and pollinator plantings).
Continuous bloom: stagger plantings so something is flowering from May–October to fuel multiple generations.
Seasonality (Upper Midwest snapshot)
Common from late spring through fall; farther south it can be present much of the year. Expect adults on flowers June–October around Chicago, with peaks tracking aphid booms on host plants and late-season composites.
Range
Across the lower 48 and southeastern Canada, extending south through Mexico, the West Indies, and into South America; abundant in the Midwest.
Design & Habitat Tips
Plant in clusters (3–5 plants per species) to make blooms more visible to hover flies.
Mix flower shapes (umbels, daisy-types, and minty spikes) for foraging diversity.
Leave leaf litter & standing stems through winter for overwintering pupae.
Avoid broad-spectrum pesticides; tolerate some aphid colonies.
Sunny sites preferred for nectar plants; woody aphid hosts can be in sun or part shade.
