**Lesser Mealworms** (*Alphitobius diaperinus*) are a common species of darkling beetle whose larvae are severe pests in poultry and livestock operations, particularly those with deep litter systems (broiler houses). The larvae (worms) feed on decaying organic matter, spilled feed, and feces, but the primary conflict is the destruction of insulation and structural materials when the larvae bore into them to pupate. They also serve as intermediate hosts for several poultry diseases.
Taxonomy and Classification
Lesser Mealworms belong to the order Coleoptera, family Tenebrionidae (Darkling Beetles), sharing the family with the common mealworm. They undergo complete metamorphosis. They are highly resilient and adaptable to a wide range of organic materials. The adult beetles are long-lived and can quickly re-infest facilities after cleaning.
Physical Description
Adult Lesser Mealworms are small, black or dark brown beetles, about 1/4 inch long.
- **Appearance (Key ID):** Oval, shiny, black beetles.
- **Larvae (Mealworms – Key ID):** Elongated, cylindrical, smooth, yellowish-brown larvae (like small, dark wireworms).
- **Location:** Found burrowing deep in litter (manure/bedding) or tunneling in wooden beams and insulation.
- **Damage Sign:** Extensive **tunneling** and frass within insulation foam (e.g., polystyrene or polyurethane) under floors or within walls of poultry houses, leading to heat loss and structural damage.
Distribution and Habitat
Lesser Mealworms are cosmopolitan (found globally). Their preferred habitat is high-density animal confinement facilities (poultry, pig, and dairy barns) where large amounts of moist, organic litter and manure accumulate, providing both food and warmth.
Behavior and Conflict
The conflict is structural damage, disease transmission, and economic loss.
- **Structural Damage:** Mature larvae leave the litter and bore into insulation (foam or fiberglass) and wood to create a pupal cell, severely reducing the R-value of the insulation and increasing heating costs.
- **Disease Vectors:** They can carry and transmit several economically important poultry pathogens, including **Salmonella**, **E. coli**, and **Marek’s Disease** virus, complicating flock health.
- **Predation:** The beetles and larvae will occasionally bite chicks, causing minor injury and stress.
Management and Prevention
Control is integrated pest management (IPM), with a heavy focus on chemical and structural controls.
- Minimize tunneling opportunities by using **beetle-resistant insulation** (e.g., concrete or foam with resistant coatings).
- Seal all cracks and crevices in the floor and walls where they might hide.
- Remove all litter and organic material between flocks, and allow the facility to dry completely.
- Apply residual insecticides directly to the exposed concrete/soil floor and structural elements after litter removal but before new bedding is introduced.
- **Insect growth regulators (IGRs)** may be used to disrupt the development cycle.
Conservation and Research
Lesser Mealworms are managed as high-priority veterinary and sanitation pests. Research focuses on developing new, safer insecticides, exploring biological controls, and designing building materials (insulation, flooring) that physically deter the boring larvae.