In nature, bacon beetles (Dermestidae) play an important role in ecosystems by helping to clean up animal carcasses. In warehouses and living rooms, however, insects are among the most feared material and storage pests. Leaving pet food or food unlocked, or leaving litter indoors for too long, is an attractive food source for larvae of the beetle.
Happen
Almost 900 species of bacon beetles (Dermestidae) occur worldwide, including around 70 in Germany. The best-known and most common representative of the family is the common bacon beetle (Dermestes lardarius), which originally comes from Europe. However, the increasing mobility of people and the exchange of goods in the course of globalization ensure its further spread, so that the beetle can be found on almost every continent today.
Look
The common bacon beetle goes through different stages in its development. From the egg to the adult beetle, the insects therefore have a very different appearance. But they are also easy to recognize for the layperson, as they have characteristic features.
Adult beetles
The common bacon beetle is easy to distinguish from other beetle species. Although the pest is not particularly large, it has an unmistakable appearance. While its head, pronotum and lower elytra are colored black, there is a conspicuous lighter horizontal stripe on the upper elytra.
- Length: almost 1 cm
- Shape: elongated oval
- front elytra: yellowish to light brown hairy
- with 3 black spots on each elytra
- rear elytra: black
- Antennae: Clearly separated, three-part club as end member
Stefanlindmark, Dermestes lardarius, crop from Plantopedia, CC BY-SA 3.0
eggs
Dermestes lardarius eggs are tiny and glossy white in color. The female does not lay her eggs all together, but usually in clusters of around a dozen at a suitable food source.
- Length: 2mm
- Diameter: 0.3mm
larva
In contrast to the adult beetles, the larvae of the bacon beetle shy away from the light and prefer to retreat to dark places. At this stage of development, they need to eat a lot to grow quickly. Since the skin of beetle larvae does not grow with it, they shed their skin several times. The larva is also easily recognizable by its appearance:
- Length: 5 to 15 mm
- Shape: oblong-oval
- long brown hair
- clustered
- resemble hairy caterpillars
- two strong hooks on penultimate limb
- three pairs of legs on the front body
nymphs
After molting several times, the larva assumes a different shape. She becomes a nymph that already resembles the bacon beetle a little. Depending on the temperature, they need between one and several months for their development into adult insects. The nymphs are rarely seen as they dig deep into their hiding place.
- Length: 7 to 10 mm
- ivory and soft-skinned
- Shape: oblong
- short, fine hairs
way of life
In nature, the common bacon beetle usually overwinters in the pupal stage. If the temperatures rise above 16 degrees in April, the insects hatch and swarm out. Their ability to fly is well developed. They can also travel long distances in search of a partner. After fertilization, the female lays 100 to 200 eggs on a suitable food source. If it is warm enough, it only takes ten days for a larva to hatch from an egg. The adult larvae of Dermestes lardarius burrow into protected substrates to pupate. This includes:
- wood
- cardboard
- paper
- styrofoam
- mortar
By the way: The pupae are relatively tolerant of drought and cold. Even at minus seven degrees Celsius, they survive for about two months.
Life expectancy
Under optimal conditions (25 degrees and 65% relative humidity), the development time of the larvae is only around seven weeks. Here in Germany there is usually only one generation per year in the wild. Several generations per year can develop in the apartment or in a warm storage room. Common bacon beetles have a life expectancy of up to 300 days at room temperature. If temperatures rise or fall over a long period of time, the beetles will die after just a few weeks.
nutrition
While adult bacon beetles feed exclusively on pollen and nectar, their larvae need animal food sources for development. In nature, bacon beetle larvae are primarily scavengers. They thus take on an important task in natural waste disposal. They eat animal carcasses with skin and hair bare down to the bone at a rapid pace.
gailhampshire from Cradley, Malvern, U.K., Larder or Bacon Beetles. Demestes lardarius - Flickr - gailhampshire, crop from Plantopedia, CC BY 2.0
harmful effect
In the human environment, the beetle is feared as a material and hygiene pest. If the insects appear in droves, the damage caused by feeding in warehouses, museums, supermarkets and private households can be very high. Biting or scraping a product or food with the mouthparts is often enough to make it unfit for consumption, use or sale. The preferred materials that bacon beetle larvae eat include:
- Meat and meat products (such as sausage, bacon, and ham)
- animal feed
- hard cheese
- dried fish
- egg noodles
- leather
- stuffed animals
- insect collections
Since the beetles are also able to digest keratin, they can also feed on feathers, fur or even woolen textiles. In addition, plant products such as chocolate or cocoa beans are popular because of their high fat content.
danger to humans
Common bacon beetles do not transmit dangerous diseases, so they do not pose a direct threat to humans. However, sensitive people should be careful, because insect droppings can trigger allergies or lead to gastrointestinal upset. In addition, the larvae are able to shoot poisonous arrow hairs on their abdomen in case of danger and thus trigger irritation of the skin and respiratory tract. The common bacon beetle can neither sting nor injure human skin with a bite. Nobody has to fear a bite from a larva either.
detect infestation
Common bacon beetles are mainly nocturnal, but they orientate themselves by the light and can thus also get into the house. In most cases, however, eggs or larvae are introduced through contaminated animal feed or food. In the case of a heavy infestation, the larvae can not only cause damage to materials of animal origin. If there is a shortage of animal feed, the pests also like books or wooden boards. The damage caused by biting or scraping with the mouthparts is comparable to that of moths. Thread-like droppings also indicate the shy beetle. The eggs are quite small and therefore not easy to spot. However, these are always placed near a food source.
pheromone trap
If you suspect that the bacon beetle has settled in your home, it is best to get a special trap for the insect. This is a box or cardboard coated with glue, which is provided with species-specific messenger substances (pheromones). These pheromones are normally released by the reproductive females to attract the male Dermestes lardarius. The bugs fly towards the trap and then stick to the glue.
A pheromone trap is only suitable for identifying a bacon beetle infestation. Complete control with such a trap is not possible, because if a beetle has already reproduced beforehand, the trap is not very effective. Larvae and females do not respond to pheromone traps at all.