Rhyzobius foresteri (Mulsant, 1853)

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POLYPHAGA Emery, 1886

CUCUJOIDEA Latreille, 1802

COCCINELLIDAE Latreille, 1807

COCCIDULINAE Mulsant, 1846

Rhyzobius Stephens, 1829

Native to Australia, this species has been introduced to many countries across the world as a control agent of various scale insects on trees and crops. It has been used widely across southern Europe since the 1980s to help control Olive Scale (Salssetia oleae (Olivier, 1791) (Hemiptera; Coccidae), and has recently been reported from France, Italy, Belgium and the UK. This northern spread seems to be increasing but the species is not always so invasive; it was introduced into San Jose and Santa Barbara in 1892 to help control various scale insects and soon became established but since that time has remained only in coastal parts of California. It was first reported from the UK from London in 2014 and since that time it has spread rapidly across the southeast, reaching north to Leicester. Adults have been found throughout the year, they overwinter among litter or bark near trees and shrubs or among evergreen foliage and are active over a long season from early spring, peaking in spring and again in the autumn. Typical habitats are parks and gardens where they occur on a range of ornamental trees and shrubs but they also occur in well-shaded woodland, often on Holly or extensive growths of Ivy. Little is known of the biology in the UK but some observations have been made in Japan where the species was first recorded in 1995 from colonies of the Mango Shield Scale (Protopulvinaria mangiferae Steinweden, 1929) (Hemiptera; Coccidae). Mating occurs through the spring and summer and females oviposit under or beside scale insects; eggs are oval, pale yellow and about 0.6X0.25 mm, they are laid singly and usually placed horizontally. Most females repeatedly oviposit beneath or among scales and the total number of eggs produced by females averaged 439. Eggs take on average 6 days to develop. Larvae pass through four instars; development is rapid but depends on temperature and food availability but averages 13 days. When fully grown the larva attaches itself to a secluded part of the plant and pupates, and adults emerge after 5 days or so. Adult lifespan was measured at about 95 days for both sexes. Prey species have not been recorded from the UK but given the very wide range of scale insect hosts recorded throughout the species wider range it is likely to be very adaptable in this respect. Adult beetles may be swept or beaten from foliage at any time of year and they are among the few UK ladybirds that are attracted to UK light.

Rhyzobius forestieri

Rhyzobius forestieri

2.7-3.7 mm. Convex and broadly-oval, dorsal surface unmetallic shiny black with wavy pale pubescence, abdomen red, contrasting with the shiny black ventral surface, appendages black except for the pale antennal bases. Newly eclosed specimens have pale orange elytra and underside but darken within a few hours. Entire dorsal surface finely and randomly punctured. Eyes coarsely-faceted.  Antennae reaching into the basal half of the pronotum; 11-segmented with a long 4-segmented club. Pronotum broadest across obtuse posterior angles and narrowed to rounded anterior angles, basal margin produced back to the centre. Elytra smoothly curved from rounded shoulders to a continuous apical margin, surface without striae or larger punctures.