Rhyzobius
Stephens, 1829
Species Guides
2- Rhyzobius forestieri(Forestier's lady beetle)
- Rhyzobius lophanthae(purple scale predator)
Rhyzobius is a of small lady beetles (Coccinellidae) in the tribe Coccidulini. The genus was established by J.F. Stephens in 1829 (published 1832) and contains approximately 106 recognized worldwide. Members are specialized of scale insects (Coccoidea), particularly armored scales (Diaspididae). Several species, notably R. lophanthae and R. ventralis, have been widely introduced as agents against pests in temperate regions globally.
Pronunciation
How to pronounce Rhyzobius: /rɪˈzoʊbiəs/
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Distribution
of Rhyzobius have been recorded on every continent. The has native in Australia, with several Australian species (R. lophanthae, R. ventralis, R. forestieri) introduced to North America, Europe, and other temperate regions for . Distribution records exist from Denmark, Norway, and Sweden.
Diet
Specialized of scale insects (superfamily Coccoidea), including armored scales ( Diaspididae) and soft scales. R. lophanthae has been documented feeding on Aspidiotus nerii, Aonidiella aurantii, Chrysomphalus aonidum, and Aulacaspis yasumatsui.
Host Associations
- Aspidiotus nerii - preyHemiptera: Diaspididae
- Aonidiella aurantii - preyHemiptera: Diaspididae
- Chrysomphalus aonidum - preyHemiptera: Diaspididae
- Aulacaspis yasumatsui - preyHemiptera: Diaspididae; pest of cycads
- Cycas micronesica - associated plant plant of prey A. yasumatsui
Life Cycle
Complete with , four larval instars, pupa, and stages. Development is temperature-dependent. For R. lophanthae, mean time ranges from approximately 26 days at 30°C to 34 days at 26°C under laboratory conditions. Egg-to-adult development takes 27.1 days on Aspidiotus nerii at optimal temperatures.
Behavior
use volatile chemical cues to locate -infested plants. R. lophanthae demonstrates olfactory preference for scale-infested mature plant leaves over seedling leaves. Larvae produce wax as a defensive covering. Both intraguild and have been documented in some .
Ecological Role
of scale insects that function as agents in natural and agricultural . R. lophanthae is commercially available and widely used for control of pests in citrus and ornamental crops.
Human Relevance
Several are important agents. R. lophanthae (purple- ) has been introduced to multiple continents for control of diaspidid scale pests. R. ventralis and R. forestieri were historically used for California citrus pest control, though taxonomic confusion between these species complicated early biocontrol efforts. The is commercially reared for releases.
Similar Taxa
- LindorusFormerly treated as a separate ; R. ventralis and R. forestieri were historically classified under Lindorus. Now synonymized with Rhyzobius based on phylogenetic and morphological studies.
- ScymnusHistorical confusion in early literature; R. ventralis was originally described as Scymnus ventralis and S. restitutor. Distinguished by antennal structure and genitalia.
Misconceptions
The name is frequently misspelled 'Rhizobius', which was Stephens' original 1832 publication error. However, Stephens had used 'Rhyzobius' in 1829 as a , and this spelling is now conserved. 'Rhizobius' is also an obsolete suppressed name for a of woolly aphids (Aphididae: Pemphigus), creating ongoing nomenclatural confusion. Historical literature referring to 'R. ventralis' often conflated two distinct (R. ventralis and R. forestieri), leading to inconsistent results in introduction efforts.
More Details
Taxonomic history
The was established by J.F. Stephens in 1829 as a , then validly published in 1832 with the misspelled 'Rhizobius'. Louis Agassiz formally proposed 'Rhizobius' in 1846, but this was rejected. The genus belongs to tribe Coccidulini, sometimes treated as subtribe within Coccinellinae.
Biocontrol efficacy factors
Success of Rhyzobius as agents depends on prey (armored vs. soft scales), plant characteristics, climate matching, and avoidance of intraguild . Temperature optima around 28°C maximize reproductive output for R. lophanthae.
Sources and further reading
- BugGuide
- Wikipedia
- GBIF taxonomy match
- iNaturalist taxon
- NCBI Taxonomy
- Catalogue of Life
- Farklı sıcaklıkların Rhyzobius lophanthae Blaisdell (Coleoptera: Coccinellidae)’nin biyolojisi üzerindeki etkileri The effects of different temperatures on the biology of Rhyzobius lophanthae Blaisdell (Coleoptera: Coccinellidae)
- Scale Morphology Effects on Feeding Behavior and Biological Control Potential of Rhyzobius lophanthae (Coleoptera: Coccinellidae)
- Life-history attributes and biocontrol potential of the Purple coccidophagous ladybird, Rhyzobius lophanthae (Coleoptera, Coccinellidae)
- Rhyzobius ventralis (Erichson) and R. forestieri (Mulsant) (Coleoptera: Coccinellidae), their biology and value for scale insect control
- Studies on morphology and biology of immature stages of the predator Rhyzobius lophanthae Blaisdell (Col.: Coccinellidae)
- Life-history attributes and biocontrol potential of the Purple coccidophagous ladybird, Rhyzobius lophanthae (Coleoptera, Coccinellidae)
- Rhyzobius lophanthae Behavior is Influenced by Cycad Plant Age, Providing Odor Samples in a Y-tube Olfactometer
- ‘Rhyzobius ventrails’ (Coleoptera: Coccinellidae), its constituent species, and their taxonomy and historical roles in biological control
- Adult morphology and life cycle under constant temperatures of the predator Rhyzobius lophanthae Blaisdell (Col., Coccinellidae)
- Biocontrol Potential of a Commercially Available Predator Rhyzobius lophanthae Blaisdell (Coleoptera: Coccinellidae) Against Diaphorina citri Kuwayama (Hemiptera: Liviidae).