Because it is 12 to 18 mm long, the yellow mealworm (Tenebrio molitor) is hard to overlook when it is crawling through snow-white flour. The freshly hatched beetle is brown at first, and then turns black with light stripes on its wing cases. The females lay 150 to 200 sticky eggs in the food. The hatched larvae are the familiar mealworms, with a length of up to 28 mm. It may take a year and a half before the mealworms turn into beetles. Massive infestation is therefore fortunately rare. The adult beetles live for about 4 to 6 weeks.

Drugstore beetles and mealworms not only eat any pastry and bakery products, they also soil them as well. The flour turns lumpy and smells mouldy. They prefer leftover wheat and flour waste. The drugstore beetle's larvae can bore passages or cavities in rotten wood or insulating materials, with the aim of finding a suitable place to pupate. In addition they can cause parasitic infections. Among other things mealworms transmit parasitic worms. In the case of the drugstore beetle the place of origin is often a bird's nest.

Preventive measures and control

• Keep food cool and dry
• Find the cause of the infestation, i.e. perhaps look for hidden food left lying around (including animal food), which would go unnoticed at first sight
• Immediately remove and destroy infested foods, and if it looks alright keep it in a deep freezer for three days
• Vacuum-clean storage cupboards thoroughly (the cracks and crevices especially)
• Keep new stores in sealed containers (jars, boxes)

The basic rule is:

• Do not use insecticides in storage cupboards and next to foodstuffs