Lesser Mealworm: Life Cycle, Risk & Control

Alphitobius diaperinus, often known as the darkling beetle, buffalo beetle, or lesser mealworm, is one of the most common insects found on the floor of chicken barns. It has long been recognized as a widespread pest worldwide, and while its origins are unknown, it is thought to have originated in Sub-Saharan Africa and spread along global trade routes. 

The beetles devour spilled feed and chicken feces, and thereafter they’re fed on by the chickens. This results in a risk of disease transmission, particularly Salmonella. These insects are tough to control because they multiply quickly. They hide in crevices in walls and other small areas to avoid standard cleaning and disinfecting operations.

Different Stages of the Lesser Mealworm

What are lesser mealworms?

The mature lesser mealworm beetle measures around 6mm in length and has a broad oval form. It has a shiny black or brown body with a reddish-brown elytra that vary in color from individual to individual and changes with age.

With puncture-like impressions that cover a large portion of the body surface, the tips of the antennae are paler and coated in tiny yellowish hairs. The longitudinal grooves on the elytra are shallow.

They have the ability to move quickly. Each female lays an average of 200 to 400 eggs. Since they live in litter, it is assumed that they do not cause any harm or pose any problems. On the other hand, the lesser mealworms have been found to attack the digestive systems of sick birds. 

In addition to that, lesser mealworms are aggressive, destroying the eggs and larvae of helpful insects like predaceous mites and pseudoscorpions, which are attracted to the litter. 

Mealworms have also been linked to the destruction of nuisance insect eggs and larvae, such as fly eggs and maggots. To help with fly management, the bug is placed into new chicken houses or recently cleaned houses in several areas.

To manage lesser worms, reduce the light visible from the house and set up light elsewhere to attract the mealworms in areas near homes afflicted with lesser mealworms.

During the day, a perimeter pesticide like permethrin can be put around the house to kill beetles hiding in the grass, bushes, siding, porches, and other areas. A blacklight electrocuting unit can also be placed outside the house.

Lesser mealworm life cycle

Eggs, larvae, pupae, and adults are the four stages of development for mealworm beetles. The time it takes for insects to progress through these stages is determined by the temperature of their surroundings and the food availability. A mealworm’s life cycle might last anywhere from four months to a year.

1. Egg

Female mealworm beetles prefer dark, quiet spots to lay their eggs in late spring or early summer, and the mealworm life cycle begins. They frequently lay eggs in grain, meal, or flour containers whenever they reproduce in buildings. Females usually lay 300 white, bean-shaped eggs at a time.

2. Larvae

Initially, they are milky white with slender, segmented bodies that turn yellow-brown after a few days. The pests feed on their surroundings and grow to be about an inch long, shedding their skins multiple times. This may contaminate food stockpiles in the process.

3. Pupa

Pupa mealworms are larvae until temperatures fall below the freezing point, at which point they transition into pupae and hibernate. Pupae are yellowish-white in color and have a thick, C-shaped form. As they approach adulthood, they become darker.

4. Beetle

Adult beetles emerge from their pupal condition as summer approaches. The pests start off white and orange in color but turn black or yellowish after a few days. Mealworm beetles move slowly, but their ability to fly allows them to traverse and infest new locations easily. Adults have a lifespan of 3 to 12 months.

Long-term infestations and exposure to mealworm adults, pupae, and larvae, can cause allergic reactions like headaches and asthma. This is a concerning issue for homeowners.

Lesser mealworm importance

Lesser mealworms have the following uses:

  1. Mealworms are high in essential nutrients and protein and are far more environmentally friendly than meat. Mealworm powder contains 55 percent protein, all essential amino and fatty acids, and more iron than sirloin beef in a single serving. Pets like leopard geckos eat most worms, including lesser mealworms and wax worms as well.
  2. They are also used as bait when fishing since mosh fish respond well when a lesser mealworm is used.
  3. They help control other parasites found in your barn.

As such, you can find a balance with them on the farm. Besides being used as food for turtles and other reptile pets, they help keep the farm healthy through their control of parasites.

Damage caused by lesser mealworms

The lesser worm problem will grow drastically due to the steady accumulation of high numbers in your broiler house litter. As there is enough food for these scavengers, they need a little moisture from waterers or leaking pipes to thrive.

Another reason is that both adults and larvae are more active at night than during the day. Therefore, many adults and larvae may be present before the farmer notices a problem.

1. Structural damage

When the larvae leave the litter searching for a dry place to pupate and transition to the adult stage, structural damage begins. They may tunnel into polystyrene insulation or even timber beams and supports at this point. 

If the litter is overcrowded, the larvae are more likely to leave. Extensive tunneling can wreak havoc on insulation and necessitate costly repairs.

2. Invasions 

Thousands of beetles invading homes or buildings have resulted in drastic measures to eliminate the insects, including lawsuits filed by homeowners against the producers. This commonly happens when litter or manure from badly infested poultry barns is spilled across fields. 

If this is done when the weather is warm, the beetles will flee the field and may come into homes unexpectedly. Beetles are attracted to lights of various intensities at night, ranging from a single candle to a car’s headlights. They appear to be most likely to fly between the hours of 8 p.m. and 12 a.m. There’s no way of knowing how far they can fly.

3. Diseases 

Disease reservoirs are areas where diseases can persist and endanger flock health. Lesser mealworms gorge themselves on the carcasses of dead and dying birds.

Pathogens such as Salmonella, E. coli, and the infectious bursal disease virus can contaminate them. After consuming infected larvae or adult litter beetles, healthy birds can be affected.

How to control lesser mealworms

Their continuous accumulation of high numbers in broiler house litter can cause lesser mealworm problems. Because these scavengers have enough food, all they need is a little moisture from watering cans or leaking pipes to thrive.

Due to the fact that both adults and larvae are more active at night than during the day, a large number of adults and larvae may be present before the producer discovers a problem.

The main options for controlling lesser mealworms include:

1. Chemical control

Insecticides are commonly used to manage lesser mealworms, although they are more effective when combined with other nonchemical treatments.  Some growers have also experienced insecticide failures because of long-term reliance on a single insecticide or insecticide class.

Insecticide options have narrowed in recent years, but a few new insecticides have become available, resulting in a net increase in the number of insecticide classes available to control lesser mealworms. 

Producers should utilize this by alternating insecticide classes to reduce the risk of insecticide resistance and tolerance. Pyrethroids, organophosphates, spinosyns, neonicotinoids, and insect growth regulators are among the insecticide classes available for lesser mealworm control in chicken houses.

2. Biological control

Natural enemies of lesser mealworms have been found. The fungal pathogen Beauveria bassiana has shown the most biological control capacity for any of them. Strains that are highly pathogenic to the lesser mealworm have already been identified and are currently under study.

In reality, at least one Beauveria bassiana product is commercially accessible. Steinernematid nematodes have also been studied as a potential biological control, but to date, they have not been shown to provide long-term control. 

Other organisms, such as the entomophilic protozoa, have been discovered in lesser mealworms’ larvae and adults. Mites that are parasitic on lesser mealworm eggs may also give some control.

While lesser mealworms are some of the best liver feeders for insects, most of the animals that feed on them cant be used to control them, given their high breeding rates.

3. Mechanical and cultural control

Using environmental conditions or increasing sanitary practices are examples of non­chemical cultural approaches. Frequent cleaning, for example, is one of the most effective ways to control the lesser mealworm.

This method, however, is not always practicable because it is expensive, consumes a lot of time, and the crop or pastureland on which to apply the litter may not be readily available. 

Cleaning out residences during the winter months or opening curtains between flocks to allow the temperature in the house to drop below freezing to kill lesser mealworms is another non-chemical control strategy. It is important to note that frigid temperatures can kill birds and cause water and pipe damage.

Another cultural way is to prevent damp spots under waterers by repairing leaks, using extra waterers while the litter dries, or moving waterers to avoid leaking. Lesser mealworms will have less food available if management measures such as collecting up mortalities and cleaning up spilled feed are used on a daily basis.

Final Thoughts

This article should be of great help and use to you so that you can now identify a lesser mealworm and contain it. With focused effort, you can get rid of these mealworms and even use them to control other pests on the farm. 

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