Stable fly
their small (~1 mm long), white, sausage-shaped eggs (singly, or in bunches of 25–30) in humid areas with large amounts of decaying organic matter, such [...] the eggs in 1–4 days. They are typical maggots ranging in size from 5–12 mm long, and they pass through three larval instars within 10–30 (or more) days [...] believed they first originated somewhere in Eurasia. Stable flies superficially resemble house flies, but are lighter in colour and have biting mouth parts.