Caesar Greenbottle Fly (Lucilia caesar) — identification, habitat & look-alikes

The Caesar greenbottle is a shiny, metallic-green blow fly of Europe, Asia, and North Africa. It is not known to live in North America, so the green bottle flies you see in the US are other species, such as the very similar Illustrious greenbottle (Lucilia illustris).

Appearance

Appearance: About 1/4–3/8 in (7–10 mm) long, bright metallic green that turns more bronze with age, with reddish eyes. Males' eyes nearly touch; females' are set apart.

Look-alikes

Illustrious greenbottle flyLucilia illustris

Practically impossible to tell from a photo. Experts separate them by the male genitalia or the shape of the female's abdominal tip under a microscope. Of the two, only L. illustris lives in North America.

Why they get mixed upSame size and color; scientists once debated whether they were the same species.

Common green bottle flyLucilia sericata

Look for the tiny scale at the base of the wing (basicosta): pale in L. sericata, dark in L. caesar. L. sericata also has three pairs of bristles down the middle of the back of the thorax behind the suture, vs. two in L. caesar. A close-up photo is needed.

Why they get mixed upBoth are shiny green flies that gather at and garbage.

Where it lives

Typical habitats: Woodland edges
Fields
Flowers and sunny foliage
Range: Europe, Asia (including Korea, Japan, and China), and North Africa. You can't see it in the wild in the US.
Preferred conditions: In Britain it is usually seen on flowers and vegetation or sunning in a sheltered spot, and it rarely comes indoors.

Behavior

Diet: Adults feed on pollen and nectar. Larvae (maggots) feed mainly on carrion.
Activity: In Britain adults fly from April to October, peaking in June.

Life cycle

Reproduction: Females lay eggs on carcasses, favoring soft parts shaded from the sun.
Larva: Maggots eat flesh quickly. Occasionally they infest wounds on living animals, which can be a problem in some sheep-farming areas of Europe.