Lady Bugs

Overview

As you may have heard, people call ladybugs with several common names depending on what part of the world you are at. Ladybirds, ladybird beetles, lady beetles, and Halloween lady beetles are the most known ones. Ladybugs have a critical role as beneficial predators of soft-bodied arthropods, such as aphids and scales. They also have traditional values in some cultures. For example, the presence of lady beetles in a house is often considered a symbol of good luck. However, in this article, we will cover only the multicolored Asian lady beetles (MCALB), Harmonia axyridis (Pallas) as seasonal structural pests; while, other species of lady beetles are beyond the scope of our discussion.

In 1916, the MCALBs were first introduced to North America from Asia to manage aphids. Henceforth, various releases of this species were carried out in different parts of the US. Abnormally, in the fall of 1988, numerous adults of this species were found entering homes in Louisiana. Several years later, MCALBs were found well established throughout the country.

Before the abnormal outbreak of the MCALB population, we used to tell people, just pick up the little guy and let him go outside, or vacuum them up. Today, they've become a quite big fall invader problem. The MCALB has been described as the most invasive lady beetle on Earth. In North America alone, they have been found feeding on 36 different species of aphids and other pests, and have greatly reduced the number of native lady beetles in North America. In addition and contrary to popular belief, these beetles can and do bite humans, and are a source of allergic reactions that range from sneezing to asthma depending on the sensitive individuals. Moreover, dead insect bodies of seasonal invaders inside wall voids, cracks and crevices attract dermestid beetles, such as hide beetles, larder beetles, carpet beetles, etc. They also attract ants, especially carpenter ants. However, unlike mosquitoes, the bite of MCALB is similar to a pinch and no blood meal is taken from the person being bitten.

Facts

There are about 5,000 species of lady beetles worldwide and over 400 species in North America.
MCALBs were first introduced to North America for biological control of aphids in California in 1916, and have since spread reaching Canada in 1994.
In Asia, the adults of MCALBs habitually seek cracks and crevices in cliff faces to hibernate, while in the USA, cliff faces are not common, therefore they have elected to hibernate over-winter, in and around buildings instead.
In nature, the population of MCALB consists of 50% males and 50% females. However, inside houses, it has been estimated that 66% of MCALB are females and 34% are males.

Identification

Adults are about 1/3-inch long
Unlike most lady beetles, MCALB adults have various color patterns, such as, orange with black spots, red with black spots or solid orange with no black spots
Adults have a pattern of W or M-shaped mark on the thorax

Biology

Both adults and larvae are predators. They feed on aphids and soft-bodied arthropods. Adult MCALBs consume about 90-270 aphids per day, while larvae consume 600-1200 aphids during their development.
Females lay eggs in clusters of 20-30 eggs on the underside of leaves usually near aphid colonies.
Eggs hatch in 3-5 days.
Larvae develop through four instars before they pupate within 11 days.
Pupae stage usually last 5 days.
The life cycle from egg to adult requires about two to four weeks.
Between late September and late October, adults fly to over wintering sites.
Healthy MCALBs can live up to 3 years depending on the temperature and food availability.
In the USA, there are two generations of multicolored Asian lady beetles per year.

Habits

As the cold weather approaches, food availability often become challenging for many insects. Additionally, environmental cues, such as temperature, daylight, and relative humidity, along with species-specific developmental factors promote specific insects, including MCALBs to invade homes.
There is some controversy about what is involved in the orientation of the beetle's overwintering flight. Some researches have indicated that MCALBs orient themselves towards tall buildings or hills, but may encounter your building on the way. While other studies have mentioned that they are attracted to contrast, such as shadows or dark shutters, etc., which loosely resembles the white cliff faces of their native habitats in Asia. Other researches have suggested that they are attracted to light-colored houses. More controversially, scientists from the North Carolina State University have pointed out in their published article that MCALBs are not visually attracted to the white colored areas nor they are oriented by any pheromones during over-wintering flight.
At over wintering sites, they congregate on the sunlit south and west parts of the building before they finally conceal themselves in protected places. In cold unheated areas or outside, these insects will seek out sheltered areas to over winter, such as cracks or crevices along walls, under siding, roofs, overhangs, or the bark of trees etc. In the heated or warmer areas of a structure, MCALBs may hide in cracks, crevices or voids in attics, crawlspaces, empty roof spaces, vent openings and ceilings.

On warm sunny days during the winter, where pests have chosen to hibernate, it is possible to see live insect activity. Obviously any insects noted indoors during the winter are not coming in from the outside; they are coming from the structure.
Temperature is an essential factor for regulating the MCALBs activity. They need 50°F to fly and 65°F to swarm.

Management

Non-Chemical Methods

In summer or before late fall, seal or caulk all cracks, crevices, voids and any possible entry openings in and around the building.
Screen all windows, doors, vents and louvers.
To reduce the number of over wintering adults, install insect light traps (ILTs) in attics, basements, crawlspaces or other potential over-wintering sites indoors. Another way to trap these insects can be done by placing sticky traps near common cluster sites or where they gain access into the structure. Remember to check traps periodically.
Vacuum adults as they appear in the building. Do not crush, as they will stain surfaces.

Chemical Methods

It is important to know that timing the pesticide application is essential to a successful management of MCALBs. Arrange with your Adam's PMP to treat the foundation and exterior parts of your homes before the MCALBs congregate and enter the building. All cracks, crevices and any possible entry sites need to be carefully treated with an EPA proven residual insecticide. A particular attention should be given to the sunny sides of the structure.
Typically one application will be needed, usually in late August, however if we have an extended summer or heavy rains, the treatment may have worn off and another treatment may be needed in late September to maintain protection. If any of these pests make it indoors, simply use a vacuum cleaner to remove them. Often indoor treatments are not needed, unless numerous insects are seen inside and pest presence is not tolerated.

Frequently Asked Questions:

Q: Why do lady beetles appear in and around houses in the fall?

A: During late fall, adults of multi-colored Asian lady beetles seek over-wintering sites to spend the winter. In their native environments in Asia, they usually over-winter in cavities of cliff faces. As an alternative, in the USA, they tend to look for cool and dry shelter in and around buildings.

Q: How do lady beetles enter houses?

A: In the beginning, they congregate on the sunny sides of the building (west and south), and as the clod weather progresses, they go deep in cracks or crevices to hibernate. If these cavities lead into the interior of the building, they will show up flying around windows.

Q: Why lady beetles continue to appear in winter?

A: Sunny and warm winter days (around 50°F) trigger the over-wintering lady beetles to wake up and move in and around the house.

Q: Do they bite or cause health related concerns?

A: They do pinch, but they do not suck blood or carry any pathogenic organisms. However, some people develop allergic reactions when they are exposed to dead multicolored Asian lady beetles or their defensive secretions.

Q: Am I going to see lady beetles next fall? Are they going to be in a big number?

A: Probably yes. However, their numbers depend on a number of reasons, including environmental and biological factors that may increase or limit their survival rates. Of course, food availability, such aphids will play an important role in their population size in nature.

Q: Will multicolored Asian lady beetles eat our food or damage our house during winter?

A: No. They feed only on insects, such as aphids and scales.

Q: Where do lady beetles go in spring?

A: In spring, as the temperature reaches about 50°F, they emerge from their hiding places, congregate on the sunny sides of the house for a while and then take off to the fields. Then, they feed, mate and continue their life cycle.

Q: What preventative measures indoors and outdoors can homeowners take to prevent the invasion of lady beetles?

A: Outdoors locate and seal all cracks, crevices, holes and any cavities that beetles may use as shelter or entry points into the house. Make sure that vent and window screens are free of holes, especially in attics and basement. Seal or caulk wherever a utility pipe, telephone or cable enters the siding. Make sure that door sweeps are in good condition and no light or a gap can be seen under the door. Additionally, make sure that the weather seal on doors and windows is tight. Early in the fall, arrange with your Adam's PMP to apply an EPA approved residual insecticide for exterior use. A thorough treatment needs to be applied to the south and west sides of the house (the sunny sides), where beetles congregate before they move to hidden sites. Inside the house, seal any cracks, crevices, voids, or cavities where beetles may hide.

Q: Why some bugs are called with different common names; what are other names of ladybugs?

A: Scientific names are usually used to provide information about the species, while common names have generally tended to be used by non-specialists, often for communication purposes. Although the scientific names of insects are fixed throughout the world, common names may vary depending on various reasons. Lady beetles have different versions of common names. For example, most North Americans call them ladybugs, but the English prefer "ladybirds" (when disturbed, these beetles secrete a sticky fluid from their joints that leaves bad smell and test, which birds try to avoid). Since one of their color forms is similar to the pumpkin color, as well as they show up in late October, some people call them Halloween lady beetles. Although they are considered annoying fall invaders in most North American homes, in another part of the world, finding a lady beetle in someone's house in winter is a sign of good luck. Moreover, in Sweden, when a lady beetle walks across the hand of a single girl, this indicates that it is measuring for wedding gloves. Anyhow, scientists use the common name "lady beetles".