News Panic over nothing? Harmless cockroaches in the home.

Cockroaches have a bad reputation as unhygienic creatures, and are therefore considered ‘pests’ by many people. If a cockroach appears in the home, panic often ensues, which in most cases is completely unfounded. There are many species of cockroaches that are completely harmless and occur naturally. These can sometimes end up in your home by accident; in recent years, we have seen this happen more and more often. Which species are these and how can you distinguish these harmless insects from the unwanted ‘house cockroach species’?

What are cockroaches?

Cockroaches are highly mobile, flattened, often brownish insects with more or less hardened front wings. They have long, thread-like antennae, long, thorny legs, and a pair of thorny protrusions (cerci) on their abdomen. The immature specimens are called nymphs and often resemble the adults, but they are smaller and have no wings.

Cockroaches are notoriously omnivorous, which means they eat almost anything. They are known as ‘opportunistic eaters’ and can survive on an incredibly wide range of food sources. A limited number of species find this food in human environments and therefore pose a problem indoors. These unwanted cockroaches are exotic species that easily adapt to the warm, humid living environment created by humans. However, the majority of all other cockroach species live outdoors in the wild and have no business indoors. In Belgium, there are several native species of forest cockroaches and a newcomer from the south: the German cockroach.

Native forest cockroaches

Forest cockroaches (genus: Ectobius) are mainly found in forests, heathland, dunes, and meadows. They live in the soil and vegetation and often hide under leaves and tree bark, in litter and moss. Forest cockroaches play an important role in nature because they break down organic material. In doing so, they support the nutrient cycle and contribute to soil health. In addition, forest cockroaches are a food source for birds, frogs, spiders, and other predators.

Forest cockroaches are naturally very shy and only become active at dusk. Two species of forest cockroaches, namely the ‘true’ forest cockroach (Ectobius sylvestris) and the northern cockroach (Ectobius lapponicus), are sometimes found in homes. This usually occurs in houses in green surroundings. The insects enter the home through cracks and crevices or through open windows and doors. Large numbers of forest cockroaches can also be brought in directly from the forest with freshly cut firewood. Since these species thrive in a humid environment, they die fairly quickly indoors. It is therefore advisable to guide these useful insects back outside as quickly as possible.

How can you recognize these two native species?

The northern cockroach has a body length of 9 to 11 mm. It is brown in color, with a black, reddish-brown, or yellow neck shield (= rounded triangular part behind the head). The female is lighter in color than the male. The wings of both sexes have clear veins. Adult specimens can be found between April and October.

The ‘real’ forest cockroach is slightly smaller (7 to 11 mm) and has a dark brown to black pronotum with a sharply defined pale edge. The wings of males are fully developed and extend beyond the end of the body, while the wings of females are greatly reduced and cover only half of the abdomen. Both males and females have wings with distinct veins and dark spots. Adults are present from April to November.

The striped cockroach

In recent years, we have received an increasing number of reports of cockroaches indoors. In almost all cases, these are striped cockroaches (Planuncus tingitanus s.l.). Like the native forest cockroach species described above, this species normally lives outdoors, where it feeds on decaying organic plant material such as fallen leaves. It owes its name to its appearance during the nymph stage: the nymphs are dark in color and have a distinct white band running across their bodies.

The exact origin of the banded cockroach is still under debate, but it is certain that it was already present in Spain and southern France in the 1980s and 1990s and spread to more northern European countries from 2005 onwards. In Belgium, it was first identified in 2011 (according to waarnemingen.be), and ten years later, the species was considered established in Flanders. Because this species originates from warmer regions, it needs more heat than our native forest cockroach species. This is why the brown-banded cockroach is more commonly found in gardens and parks in densely built-up areas, often near warm building facades. Because of this and because it is attracted to light sources, the brown-banded cockroach is more likely to walk or fly indoors than other species. However, there is nothing for this species to feed on indoors and it poses no risk. To limit any nuisance, it is advisable to remove potential hiding places around the house, such as fallen leaves.

Adult brown-banded cockroaches are active from June to December, with a peak in August. They move very quickly, but when they pause, you can recognize them by the white band between their eyes. In addition, their wings do not reach the end of their abdomen and they do not have dark spots (like the ‘real’ forest cockroach).

Pest species in the home

Of the cockroach species that can cause infestations in our homes, only two species can be confused with the native forest cockroach species and the German cockroach in terms of size (10 to 15 mm long). These are the German cockroach (Blatella germanica), the most common pest cockroach in Belgium, and the brown-banded cockroach (Supella longipalpa), which is rather rare in our country. Species larger than 2 cm, such as the Oriental cockroach or bakkerstor (Blatta orientalis), the American cockroach (Periplaneta americana) and the Surinamese cockroach (Pycnoscelus surinamensis) are not discussed further here. The presence of one of these pest cockroaches in the home requires control through a combined approach of hygiene measures and, if necessary, pesticides or professional help. Because these cockroaches can spread disease, quick action is essential!

Many cockroach species are light-shy, including German cockroaches. During the day, they hide in dark, warm, and damp places, such as near the motor of the refrigerator, behind kitchen cabinets, near water pipes, sinks, heating equipment, or under floors near heating pipes. At night, they go in search of food. German cockroaches are straw-yellow to light brown in color and have two distinct black longitudinal stripes on their neck shield, long antennae, and long wings. Their bodies are 10 to 15 mm long. Young cockroaches are 2 to 12 mm long and do not yet have wings.

Unlike the German cockroach, the brown-banded cockroach is not or only slightly light-shy and easily flies up when disturbed. It also needs less moisture than the German cockroach and can therefore also be found in drier places in the home. This species can sometimes be found in drier rooms where it hides in furniture, behind wall panels and books, or behind loose edges of wallpaper.

Brown-banded cockroaches are more difficult to distinguish from native forest cockroaches because they are similar in length (10-15 mm) and color (brown to light brown). However, they are characterized by two light-colored transverse bands across the wings and abdomen, which sometimes appear interrupted or irregular but are still clearly visible. The bands may be partially covered by the wings. The wings of the male cover the abdomen, while those of the female do not completely cover the abdomen. Males are slimmer than females. Nymphs also have two transverse pale (and two dark) bands on their bodies.