Rhyzobius lophanthae

(Blaisdell, 1892)

purple scale predator, scale-eating ladybird

Rhyzobius lophanthae is a small coccidophagous to Queensland and Southern Australia, widely as a agent. and on () and , with younger larvae crawling beneath protective covers to feed on . The has established across the southern United States since its 1892 introduction to California, as well as in Europe and Pacific islands including Guam and Rota. It exhibits temperature-dependent development with optimal reproductive performance at 28°C.

Rhyzobius lophanthae by (c) Paul Cook, some rights reserved (CC BY), uploaded by Paul Cook. Used under a CC-BY license.

Rhyzobius lophanthae view from top by Andreas Sanchez, Yannick Chittaro. Used under a CC BY 4.0 license.

Rhyzobius lophanthae (England, Kent) 1 by Barry Walter. Used under a CC BY 4.0 license.

Pronunciation

How to pronounce Rhyzobius lophanthae: //raɪˈzoʊbiəs loʊˈfæntiː//

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Distinguished from similar by small size (<3 mm), reddish- and contrasting with dark metallic , and dense short covering and elytra. Antennal has 9 . Differs from Scymnus by -level characters including tarsal structure; from other Rhyzobius by specific coloration pattern and body proportions. Sexual identification possible via fifth outline. recognizable by dark brown coloration with stout .

Images

Appearance

Small measuring 1.7–2.85 mm in length and 1.35–2.0 mm in width. and reddish- with dense short hairs of two lengths; underside similarly colored and hairy. blackish with metallic bronze sheen. with 9-segmented . 3-segmented on all legs. Fifth outline differs between sexes. dark brown with stout ; and pupal described but less conspicuous.

Habitat

Associated with plants hosting ; found on citrus, cycads, and other plants infested by . In range, occupies agricultural and natural settings where occur. Laboratory rearing successful at 60% with long-day .

Distribution

to Queensland and Southern Australia. and established in California (since 1892), throughout southern United States, Europe, Guam, Rota, and Azores (Flores, Graciosa, Pico, São Jorge, São Miguel).

Diet

Specialized of (), including Aspidiotus nerii, Aonidiella aurantii, , Saissetia oleae, and Aulacaspis yasumatsui. Also feeds on and other . Young crawl under protective covers to feed on .

Host Associations

Aspidiotus nerii - oleander ; supports complete development with 0% mortality in laboratory studies
Aonidiella aurantii - ; development slower (48.8 days) with high mortality (84%)
Chrysomphalus aonidum - used in studies at varying temperatures
Saissetia oleae - olive ; target of original California introduction
Aulacaspis yasumatsui - cycad ; to Guam and Rota for control
Paraserianthes lophantha - associativeoriginal collection ; specific epithet derived from this association
Cycas micronesica - cycad in Guam and Rota; shows preference for -infested plants over seedlings
Citrus - agricultural where used for

Life Cycle

with four larval . Development from to : 27.1 days on Aspidiotus nerii at optimal conditions; 48.8 days on Aonidiella aurantii. Temperature strongly influences development rate: at 15°C, 20°C, 25°C, and 30°C, embryo, larval instars, pupal, and preoviposition periods vary predictably. Mean time 30.866 days at 28°C. Total up to 303.751 eggs per female under optimal laboratory conditions.

Behavior

Uses volatile chemical cues to locate ; demonstrates preference for -infested mature leaves over seedling leaves in studies. Preference strength varies with air filtration: strongest in charcoal-filtered air, intermediate in unfiltered laboratory air, weakest in unfiltered in-situ air. and actively forage beneath scale covers.

Ecological Role

of ; significant agent reducing pest in citrus and other . In Pacific islands, insufficient control on cycad seedlings contributed to 100% seedling mortality, indicating context-dependent effectiveness.

Human Relevance

Widely used in programs since 1892. Commercially available for augmentative release against and other pests. Success varies with , substrate age, and environmental conditions. Research continues on optimal release strategies, cold , and artificial diets.

Similar Taxa

Scymnus speciesFormerly classified in this ; differs in modern by tarsal structure and other characters
Other Rhyzobius speciesShare -level characters; distinguished by specific coloration, size, and distribution
Generalist coccinellids (e.g., Coccinella septempunctata)Much larger (>5 mm), different color patterns, broader diet including ; R. lophanthae specialized for at smaller size