Pest profile

Steelblue Lady Beetle

Halmus chalybeus · Coleoptera: Coccinellidae[2]

Brought from Australia to Southern California in 1892, the steelblue lady beetle still helps control scale insects along the coast.[1]

Shiny metallic blue-green steelblue lady beetle on small pale yellow flowers
Shiny metallic blue-green steelblue lady beetle on small pale yellow flowers. (c) Jacqui Geux, some rights reserved (CC BY) — via iNaturalist, CC BY 4.0

How to identify it

  • Adults are metallic dark blue, green or purple, round and domed, about 1/8 to 1/6 inch long.[1]
  • Females are uniformly dark; males have orange or yellow on the head and thorax edges.[1]
  • The lower edges of the wing covers flare out into a ridge.[1]
  • Larvae carry many short, branched spines and develop dark blotches as they grow.[1]

Look-alikes

Look-alikeHow to tell them apart
Exochomus metallicusThis dark metallic blue lady beetle is the same size but covered in fine short hairs; the steelblue lady beetle is smooth and hairless.[1]

Where it lives

It occurs at least in coastal Central and Southern California, where it was introduced to protect citrus.[1]

US map: public records from 2 states since 1990 (GBIF).

Biology and life cycle

Females lay eggs near prey, mostly by scale insects, and larvae pupate in the open on plants.[1]

Egg to reproductive adult takes about five weeks in warm weather, with several generations a year.[1]

Adults often overwinter in groups in ground litter or dense lower foliage.[1]

Damage and signs

  • It eats mostly armored, soft and eriococcid scales, plus some aphids and psyllids.[1]
  • Adults eat about a dozen scales a day and larvae about 10.[1]

Health risk

UC IPM presents it only as a scale predator, with no mention of people.[1]

Control

Biological control

Help it by controlling ants, growing flowering plants and avoiding persistent broad-spectrum sprays.[1]

Common questions

What is the shiny blue ladybug on my citrus?
In coastal California it's likely the steelblue lady beetle, a scale predator.[1]
Why do some have orange heads?
Those are males; females are dark all over.[1]

Sources

  1. University of California Statewide IPM Program, “Steelblue Lady Beetle (Natural Enemies Gallery).” ipm.ucanr.edu/natural-enemies/steelblue-lady-beetle/ (accessed 2026-10-06)
  2. iNaturalist, “Halmus chalybeus taxon page (order and family).” www.inaturalist.org/taxa/244625 (accessed 2026-10-06)

Updated 2026-10-14. Built from sourced records. Spot an error? Tell us.