Olla v-nigrum

(Mulsant, 1866)

Ashy Gray Lady Beetle

Olla v-nigrum is a small () to the Americas, commonly known as the ashy gray lady beetle. The exhibits striking color , occurring in both gray-with-black-spots and black-with-red-spots forms. It has been widely outside its native range for of and , though its effectiveness is often compromised by and competition with other lady beetles. The species name refers to the distinctive V-shaped marking on the originally described by Mulsant.

Olla v-nigrum 153022806 by Sam Kieschnick. Used under a CC BY 4.0 license.

Olla v-nigrum 165435805 by Elizabeth Praetz. Used under a CC0 license.

Olla v-nigrum 249148487 by Sam Kieschnick. Used under a CC BY 4.0 license.

Pronunciation

How to pronounce Olla v-nigrum: /ˈɒl.la ˈviːˌnaɪ.ɡrəm/

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Identification

Distinguished from Chilocorus by the presence of markings on the (absent in Chilocorus) and less flared . The triangular spots sloping away from the elytral contrast with the more rounded or transverse spots of other . The black color form with red spots can be separated from Chilocorus orbus by head markings and overall body shape. Unlike the multicolored Asian lady beetle (Harmonia axyridis), O. v-nigrum does not show extreme variability in spot number within a single color . The pronotal V-marking is diagnostic when visible.

Images

Habitat

Found in both tree and at ground level. Frequently abundant during periods of peak abundance. Peak at ground level occur at the beginning of spring and towards the end of summer; in the canopy, peak abundance occurs towards the end of summer but at lower than at ground level. Associated with vegetation hosting and aphid colonies, including Leucaena leucocephala, pecan (Carya illinoensis), and various agricultural .

Distribution

to North America ( to Florida, distributed throughout continental United States), Central America (south to Argentina), and Oceania. to Hawaii and Guam for . Established in New Caledonia and Reunion Island. Released but status unknown in southeastern France, Israel, and Czechoslovakia. Recently documented on Canary Islands (first observed 2014 on Tenerife and La Palma, later Lanzarote, Gran Canaria, and Madeira in 2020).

Seasonality

Active year-round in suitable climates. Peak abundance at ground level in early spring and late summer; peak in late summer. Activity correlated with availability, particularly population cycles.

Diet

of and . Preys primarily on psyllids, including the (). Consumes various aphid : , Hyadaphis sp., Metopolophium dirhodum, Uroleucon sp., , and Myzus sp. Also feeds on and of and . Rarely preys on living (Nezara viridula), but will scavenge dead . Fourth larvae attack more readily than . occurs even when alternative is available, increasing when food is scarce.

Host Associations

Heteropsylla cubana - Neotropical , major pest of Leucaena leucocephala; target of efforts
Phalacrotophora quadrimaculata - that parasitizes , laying up to 8 on ; major mortality factor in New Caledonia
Hesperomyces virescens - Fungal causing significant mortality; co- with bassiana or brunneum increases mortality further
Beauveria bassiana - Common fungal ; O. v-nigrum shows higher mortality than Harmonia axyridis when infected
Metarhizium brunneum - Fungal ; co- with Hesperomyces virescens increases mortality
Harmonia axyridis - competitor Asian ; competition for has reduced O. v-nigrum in North America; O. v-nigrum suffer 95-100% mortality when fed H. axyridis

Life Cycle

Rapid development with short stages. stage lasts 1–2 days. Larval duration approximately 7 days, notably shorter than related . Pupal phase lasts 4–5 days. Egg-to- period approximately 16 days. Total cycle from to adult about 25 days. Mean interval between approximately 52 days. Larval viability exceeds 80% under favorable conditions. Adult longevity approximately 60 days. Larvae have elongated, segmented and remain near eggs after hatching, consuming infertile eggs.

Behavior

exhibit limited movement after hatching, remaining near clusters. occurs at measurable rates even with adequate food resources, increasing only in response to food reduction rather than food quality reduction. No sibling recognition mechanism demonstrated—cannibalism rates similar between siblings and non-siblings. Group size does not affect cannibalism frequency. and larvae are both predatory. Fourth larvae more aggressive of than adults.

Ecological Role

of pests, particularly and . Functions as a agent in agricultural and silvicultural systems. Serves as for and fungal . Subject to intense competition from the Harmonia axyridis, with which it shares resources. More susceptible than H. axyridis to and nematodes, contributing to its competitive disadvantage.

Human Relevance

Widely used in programs against and , including the and pecan aphids (Melanocallis caryaefoliae, Monelliopsis pecanis, Monellia caryella). Shows lower mortality to certain than other , making it suitable for , though high susceptibility to carbaryl limits late-season use in pecan orchards. Rearing protocols established using Anagasta kuehniella and artificial diets for mass production. declines documented due to competition with Harmonia axyridis, reducing its effectiveness as a agent.

Similar Taxa

Chilocorus orbusBlack color form of O. v-nigrum resembles this , but O. v-nigrum has markings and less flared
Chilocorus spp.Similar body shape and spotted pattern, but lack markings on and have more distinctly flared
Harmonia axyridisCompeting with extreme color variability; O. v-nigrum has more consistent spot patterns and distinctive pronotal V-marking

More Details

Etymology

The name v-nigrum derives from Mulsant's original description of the as 'adorned with a V and four black dots'

Population Status

Has become less prominent throughout North America due to competition with the Asian (Harmonia axyridis), which is less susceptible to and shares the same broad range. declines expected in South America as H. axyridis spreads to Argentina and Brazil

Laboratory Rearing

Can be maintained on commercially obtained pollen and Anagasta kuehniella ; artificial diets supplemented with yeast, , ascorbic acid, and water support but with reduced egg viability (~54.8%) compared to natural