Rhyzobius

Stephens, 1829

Rhyzobius is a of small () in the tribe Coccidulini. The genus was established by J.F. in 1829 (published 1832) and contains approximately 106 recognized worldwide. Members are specialized of (), particularly (). Several species, notably R. lophanthae and R. ventralis, have been widely as agents against pests in temperate regions globally.

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

Pronunciation

How to pronounce Rhyzobius: /rɪˈzoʊbiəs/

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Distribution

of Rhyzobius have been recorded on every continent. The has in Australia, with several Australian species (R. lophanthae, R. ventralis, R. forestieri) to North America, Europe, and other temperate regions for . Distribution records exist from Denmark, Norway, and Sweden.

Diet

Specialized of (superfamily ), including ( ) and . R. lophanthae has been documented feeding on Aspidiotus nerii, Aonidiella aurantii, , and Aulacaspis yasumatsui.

Host Associations

Life Cycle

with , four larval , , 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 leaves over seedling leaves. produce as a defensive covering. Both intraguild and have been documented in some .

Ecological Role

of that function as agents in natural and agricultural . R. lophanthae is commercially available and widely used for control of pests in citrus and ornamental .

Human Relevance

Several are important agents. R. lophanthae (purple- ) has been to multiple continents for control of scale pests. R. ventralis and R. forestieri were historically used for California citrus pest control, though taxonomic confusion between these species complicated early 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 .

Misconceptions

The name is frequently misspelled 'Rhizobius', which was ' 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 (: 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. 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 (armored vs. ), characteristics, climate matching, and avoidance of intraguild . Temperature optima around 28°C maximize reproductive output for R. lophanthae.

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Sources and further reading