Adult beetles, approximately 28mm in length and shiny, dark-brown or black, resembling many ground beetles in shape, size and colour. The mealworm themselves are the larval form. Larvae up to 20mm in length are a honey-yellow colour with hard, highly polished worm-like body.
Female beetles' can lay up to 500 eggs over a period of 3 – 5 weeks, larvae emerge after 2 weeks and feed on any available foodstuffs. Individual larvae may wander far from the food source to pupate, making it difficult for homeowners to locate the source of infestation. They are a slow breeding pest; the adult beetles evolve over 1-2 years. They can reach a size of 28mm in length. Because of the beetle's long development period an infestation is often due to poor hygiene or the remains of old food.
If lots of beetles are found in a domestic environment check in and under kitchen units for spilled or old food or infested bags of flour etc. Check in lofts and roof spaces for old birds’ nests. Clean up thoroughly and throw away any old or infested stocks of food. The area should then be thoroughly cleaned, and a residual insecticide labelled for ‘crawling insects’ can be used. Use an insecticide spray sold for 'crawling insects' that is labelled as safe for use in kitchen areas. After you have treated, be aware that further mealworms may hatch so you may need to keep treating until all the eggs have hatched out and infestation has completely gone.
Products to control Yellow Mealworm Beetle/Darkling Beetle:
Alphaban Super (500ml)
Mostyn Duo CS (500ml)