Browse Articles: Insects and Pests
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Reference: Ohio State University Extension
|The Convergent Lady Beetle|
|Common Name||Scientific Name|
|Convergent Lady beetle||Hippodamia convergens Guerin|
|Fifteenspotted Lady beetle||Anatis labiculata (Say)|
|Ninespotted Lady beetle||Hippodamia sinuata Muls.|
|Spotted Lady beetle||Coleomegilla maculata DeG.|
|Twicestabbed Lady beetle||Chilocorus stigma Say|
|Twospotted Lady beetle||Adalia bipunctata (L.)|
|Red Lady beetle||Cycloneda munda (Say)|
|Sevenspotted Lady beetle||Coccinella septempunctata (L.)|
Lady beetles, often called Ladybugs or coccinellids, are the most commonly known of all beneficial insects. In Europe these beetles are called "ladybirds." Both adults and larvae feed on many different soft-bodied insects with aphids being their main food source. Ohioans like lady beetles so much that the Convergent Lady Beetle became the official state insect in 1975.
Adult lady beetles are domed shaped, oval or convex, often shiny with short legs and antennae. Wing covers are dark, reddish-orange to pale yellow, with or without black spots or irregular marks. Some are solid black or black with a red spot. The head is concealed from above. They have three distinct tarsi (feet), and range from 1/16 to 3/8 inch long. Larvae are elongate, somewhat flattened, and covered with minute tubercles or spines. Most larvae have large, sickle-shaped mandibles (jaws) and resemble tiny, six-legged alligators blue-black with orange spots. Tiny, yellow, oval eggs are laid upright in clusters of 10 to 50 on undersides of leaves.
Life Cycle and Habits
The length of the life cycle varies depending upon temperature, humidity, and food supply. Usually the life cycle from egg to adult requires about three to four weeks, or up to six weeks during cooler spring months. In the spring, overwintering adults find food, then lay from fifty to three hundred eggs in her lifetime (tiny, light -yellow eggs are deposited in clusters of 10 to 50 each) in aphid colonies. Eggs hatch in three to five days, and larvae feed on aphids or other insects for two to three weeks, then pupate. Adults emerge in seven to ten days. There may be five to six generations per year. In the autumn, adults hibernate, sometimes in large numbers, in plant refuse and crevices.
Amount of Food Consumed
Lady beetles, both adults and larvae, are known primarily as predators of aphids (plant lice), but they prey also on many other pests such as soft-scale insects, mealybugs, spider mites and eggs of the Colorado Potato Beetle and European Corn Borer. A few feed on plant and pollen mildews. One larva will eat about 400 medium-size aphids during its development to the pupal stage. An adult will eat about 300 medium-size aphids before it lays eggs. About three to ten aphids are eaten for each egg the beetle lays. More than 5,000 aphids may be eaten by a single adult in its lifetime. The lady beetle's huge appetite and reproductive capacity often allow it to rapidly clean out its prey.
During the autumn, lady beetles crawl to overwintering sites where a few to several hundred will gather in an aggregation. The aggregation site may be located at the base of a tree, along a fence row, under a fallen tree, or under a rock. Beetles are always found under leaves which protect them from cold winter temperatures.
Sometimes beetles become a nuisance by their presence when congregating in and around homes. Some congregate in large numbers on the sunny side of the house. Caulk and seal spaces and gaps to prevent them from coming inside. Physically remove lady beetles found indoors. Since lady beetles are beneficial, insecticide treatment is not suggested.
Collecting Beetles in California Mountains
It is in the mountains that dealers collect the beetles they sell. The reason for this is that the beetles congregate in huge numbers in colonies or aggregate in the same sites year after year. Some colonies have been reported to contain as many as 500 gallons of beetles. A gallon of beetles contains from 72,000 to 80,000 adults.
Behavior of Mountain Collected Beetles
The behavior of Hippodamia convergens collected from mountain aggregations, after the month of May and then released during the summer, is quite different then the behavior of the beetles collected from aggregations during the winter and early spring months and released in the spring.
Collected after May and Released in the Summer
The beetles released in the summer do not disperse any great distance, but remain for the most part in the areas where they were released. However, their feeding habits are not normal. They will drink water, but have no appetite since they apparently are able to exist on their stored fat. Some feeding and reproduction occur, but these activities are much slower then those occurring in natural populations. Thus, summer-collected beetles cannot be relied upon to control insect pests any more than those collected in winter.
Collected in Winter or Early Spring and Released in Spring
The release made in the spring months usually involves beetles collected from the mountain aggregations in December, January, February, and perhaps as late as early March before normal beetle migration out of the mountains. These beetles can be cold-stored into late March. When winter-collected beetles from the mountains are released, they are apt to disperse quickly and widely, especially when the temperature reaches 65F and above. As a consequence, only a few beetles may remain in the area where liberated. Thus, the beetles cannot be relied upon to control a potentially growing aphid population.
Purchased Beetles Sometimes Mean Unwise Investment
There is no denying that lady beetles are beneficial insects, and are good to have around. It seems that the foregoing information clearly points out that to use shipped-in beetles in your backyard to economically manage pest insects probably is not a very good practice. It also points out that beetles collected from distant states and shipped to other locations may be of less value as a pest eater than the local beetle population. It would be better to rely upon local beetles to distribute themselves and multiply in accordance with nature's balance. Purchased H. convergens often fly away from gardens, but are effective for a greenhouse if vents are screened. Collect natural species from hay or grain fields.
How to Attract Native Beetles
Grow pollen and vector flowers (angelica, dill); grow grains and allow weeds (dandelion, wild carrot, yarrow). Wheast is a combination of whey and yeast that can be sprayed on plants to attract lady beetles (wheast is an artificial diet). Protect egg clusters, larvae, and pupae on plants. To conserve lady beetles, use only selective pesticides.
If prey is plentiful, the lady beetles will stay, lay eggs and become effective aphid predators. However, in some cases, most of the beetles will leave the area regardless of the availability of food. Suppliers' recommend "Release Rates" for gardens and greenhouses of one-half pint (about 4,500 beetles) to cover 3,000 sq. ft. (50 x 60 feet). Release beetles in the evening after watering down the area. Adult beetles are shipped in cotton bags mixed with wood shavings. Beetles are shipped air freight for quarts and larger, first class mail for smaller sizes. Prices are as follows:
|2,000 Lady beetles||$7.50|
|1/2 pint (4,500)||9.50|
|1 quart (18,000)||26.50|
|1/2 gallon (36,000)||38.00|
|1 gallon 72,000)||67.00|
|2 gallons & up||62.00|
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