There is a small apple tree in my orchard among the remaining twenty or so trees voles didn’t kill a few years back that has been host to a number of beetles this year. They include Asian lady beetles, American carrion beetles, diurnal fireflies, flower beetles and several others that moved too fast for me get a good look at. This is the first in a series of posts on the beetles from that tree.
Asiatic lady beetles (Harmonia axyridis) were brought into North America several times beginning in 1916 (and later in 1965 and 1964) in California as biological controls for aphids. The first confirmed self-sustaining populations were discovered in Louisiana and Mississippi in 1989 where they had been introduced from Japan in 1979 and 1980. They were also released in some eastern and southern states from 1978 to 1982 as aphid controls. The more recent and widespread release no doubt facilitated their establishment over much of North America in a short time. Asian lady beetles have also been intentionally introduced into Europe as aphid controls for agriculture.
Asian lady beetles are particularly useful in agriculture as they eat an aphid, Aphis glycines, also from East Asia and first documented in the US in 2000, that feeds on soy bean plants. After the initial discovery of the aphid in Wisconsin it was documented across most of the eastern US by 2003 suggesting it had been in the US for a much longer time.
They do not eat just aphids but feed on other insects and their eggs including other species of lady beetles. This eating behavior is called “polyphagous” meaning “eats many things”. This is a good survival strategy when preferred foods may be in short supply. Although they are largely insect eaters Asiatic lady beetles are also fond of sweet liquids such as the juice from ripe fruit. In grape growing regions Asian lady beetles are pests on ripe grapes which they eat. They also eat other sweet liquids such as the juice from apples and berries. Fruits with damaged skins or holes are preferred over undamaged fruits although they do eat undamaged soft skinned fruit like raspberries. High sugar content and low acidity also factor into whether Asian lady beetles will eat a certain fruit or not. Fall feeding on sugary fruit may build up carbohydrate reserves for insects that hibernate like Asian lady beetles.
Asian lady beetles exude a pungent liquid as a defense against predators. This liquid will give grapes a bad flavor that can be detected in wine made from them. This same chemical defense will also make buildings where they congregate in the winter smell bad.
Asian lady beetles typically look like the ones in the above photos but there are many variations from number of spots (none to 19) on a red, yellow or orange background or mostly black with a few to many red or orange spots. The black “W” shaped marking on the white thoracic shield (pronotum) is a good diagnostic indicator to identify the species. Body size is about 1.2 mm long.
Order Coleoptera: (Beetles)
Suborder Polyphaga: (Water, Rove, Scarab, Long-horned, Leaf and Snout Beetles)
Family Coccinellidae: (Lady Beetles)
Genus and Species: Harmonia axyridis
Two other introduced species of Harmonia are known from the US: H. dimidiata in 1926 in California and Florida and H. qudripunctata in New Jersey in 1924. The color and pattern variations of H. axyridis have been separated into many varieties and subspecies as well.
Range and distribution
The native range of the Asian lady beetle is China, Japan, Korea, and eastern Russia. It has been introduced and established in many areas of North America, in Europe, and in parts of South America and Africa.
Asian lady beetle is considered an invasive species in areas outside its native range. It should be noted that it is another case where intentional introduction has brought both benefits and problems depending on one’s economic interests.
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Weekes, L. N.; Walsh, D.; Ferguson, H.; and Ross, C. F. (2010). Impact of Multicolored Asian Lady Beetles on the sensory properties of Concord and Niagara grape juice. Journal of Food Science, 75(1):568-573.