The lesser mealworm, scientifically known as Alphitobius diaperinus, is a beetle also known as the darkling or litter beetle. Originating in sub-Saharan Africa, this insect has spread globally, primarily through the international trade of foodstuffs like rice and cereals. These beetles are strongly associated with high-density animal housing, particularly poultry farms, due to warm and humid conditions that mimic their tropical origins.
Identification and Life Cycle
The lesser mealworm undergoes a complete metamorphosis, progressing through egg, larval, pupal, and adult stages. Eggs are approximately 1 mm long, sticky, and hatch within a week. Larvae are worm-like and yellowish-brown, growing up to 15 mm long with a characteristic “tail horn.”
Larvae are highly active and avoid light, feeding on litter, manure, spilled feed, and even dead birds. They undergo 5 to 11 larval stages. After 1 to 2 months, mature larvae seek secluded sites for pupation, which can include building materials. Pupae are light-colored and develop into adults in about five to ten days. Adult beetles are shiny, dark-brown or black, oval-shaped, and measure approximately 5.5 to 6.7 mm in length, with distinctive parallel rows of tiny depressions on their wing covers. Under optimal conditions, the entire life cycle can be completed in approximately five weeks, though it can take 40 to 100 days depending on temperature and food availability.
Agricultural and Structural Impact
Lesser mealworms cause significant problems in agricultural settings, particularly in poultry houses, through both structural damage and as vectors of pathogens. Larvae burrow into insulation and wooden structures when seeking pupation sites. This tunneling leads to structural degradation and can increase heating costs by up to 67 percent in affected broiler houses.
Beyond structural harm, these beetles pose a direct threat to poultry health and serve as carriers for numerous pathogens. Chickens may consume the beetles, which can lead to nutritional stress because birds have limited capacity to digest the insect’s chitin exoskeleton. Lesser mealworms are known to transmit various bacteria, viruses, and parasites, including Salmonella, E. coli, and Marek’s disease virus. This makes them a serious biosecurity concern in poultry operations.
Control and Management
Managing lesser mealworm populations in poultry houses involves an Integrated Pest Management (IPM) approach, combining multiple strategies to reduce pest numbers and their impact. A foundational method is thorough cleaning and sanitation between flocks, including regular removal of manure and spilled feed, to eliminate food sources and breeding grounds. Physical barriers can be installed in structures to prevent larvae from accessing pupation sites within building materials.
Controlling environmental conditions also plays a role; managing moisture levels and, when houses are empty, adjusting temperatures to extreme cold or heat can help reduce beetle populations. Chemical insecticides are available, and their use should be rotated to mitigate the development of insecticide resistance. Biological controls, such as the fungal pathogen Beauveria bassiana, are also utilized, offering alternative management options.