Other insects

Identification marks

Adult: approx. 12 mm

A full-grown silverfish is around one centimetre long. It is a wingless silver insect with a body that tapers at the end. Its antennae are long and filamentous. It has three long hairs at the end of its body. The larva is similar to the adult but is smaller.

Occurrence

The silverfish lives in damp and warm indoor premises: sewers, kitchens, bathrooms and cellars. It moves around during the night and escapes quickly when the light is turned on.

A silverfish moves from one space to another through the entries of pipes, for example, and it can also crawl into apartments through drain traps. The silverfish lays its eggs in holes and cracks.

It eats materials that are high in starch. It can dissolve cellulose and can therefore eat wallpaper adhesive, glue used for book binding, mouldy paper and even photos. It can also feed on dirty textiles, leather and synthetic materials and chew holes into them.

In bathrooms, silverfish feed on hair, loose skin cells and dirt. If there are a large number of silverfish, it may be a sign of moisture damage, as silverfish also feed on mildew mycelium and spores.

At least two annual generations are produced. Silverfish can live for up to five years. They do not like dry well-ventilated spaces.

Damage

Silverfish do not usually cause any visible damage and do not often damage foodstuffs either. In theory, a silverfish can spread diseases when moving from sewers onto surfaces where food is prepared.

Prevention and extermination

You can decrease the number of silverfish by pouring boiling water into the sewers. If necessary, you can treat spots where water is used daily (such as floor drains and pipes) with a solution including pyrethrin every evening. A more long-term pesticide is used on baseboards and other places where there are cracks, in which the pesticide can remain for several weeks. After it is no longer effective, the treatment can be carried out again.

Identification marks

Adult: 20–30 mm

The adult common woodlouse (Oniscus asellus) is a flat, dark brown, jointed crustacean. The larva is similar to the adult but smaller in size. Wide, jointed shields on the back are characteristic of the isopoda. 

The common rough woodlouse (Porcellio scaber) can be distinguished from the common woodlouse by the lumps on the back shields and the tip of its two-segment antennae.

Occurrence

Land-dwelling isopods are the only crustaceans that have adapted to living on land. Although they live on land, they use a set of gills to breathe, which is why they avoid dry places.

A common woodlouse prefers damp and shady places such as rotten tree stumps and spots under thick, fallen branches and rocks. It usually moves around at night, when the moisture level of the air is higher. Land-dwelling isopods feed on rotting plans and animal waste.

Isopods are also seen in greenhouses and gardens. They may end up indoors, especially in cellars, with soil, damp hay or root vegetables.

Damage

Isopods may sometimes cause damage by gnawing on root vegetables.

Prevention and extermination

Isopods are attracted to the damp undersides of sacks, for example, and are easy to clean away.

Identification marks

Adult: Worker 7–12 mm, Queen 15–17 mm, Drone 9–11 mm

A fully grown ant is matt black and has a dark reddish-brown middle body.  Males and females have wings; workers are wingless.

Occurrence

The carpenter ant is the largest ant species in our country. It lives in coniferous forests. It can also nest in buildings. The hive can be anywhere in wooden structures, for example, the wall timbers or in the floor, and there may also be several nests in the same house.

The carpenter ant does not eat wood. Instead, it feeds on insects, the honeydew of greenflies and plant buds. It only chews wood to create space for the hive.

Winged males and females swarm during the early summer, during which they also fly inside buildings.

Damage

The hive is usually just a few timber metres long, but the hollow hive tunnels can be very harmful if they are in load-bearing structures.

Prevention and extermination

The best way to look for a carpenter ant nest is to listen to the scratching sounds, follow the swarms and feel the temperature of the wood, which rises in spots where the hive is located.

You can dispose of a hive by piercing and spraying. You can also use boiling water unless the hive is built in the structure of the house. Damaged wooden parts need to be replaced. You should also try to locate the routes the ants use outside the apartment and carry out the extermination there as well. Ant powder is a handy and effective option on the ant paths.

Identification marks

Adult: 4–5 mm

The common black ant is black and about half a centimetre long.

Occurrence

The common black ant is the most common species of ant to be found indoors in Finland. They may appear in the kitchen as large groups during the spring and summer.

Their nest is usually outside in the stone foundation of the house or under the lawn, but it may also be inside the building, in which case they may also be discovered indoors during the winter.

Damage

The common black ant does not cause any significant damage unless there are a large number of them in the apartment.

Prevention and extermination

Several pesticides are available on the market for exterminating ants. Nests should be destroyed as well as possible, although this may be difficult, as they can be very deep in the earth. If the nest is in the structures of the building, help from an external specialist is often required.

Identification marks

Adult: 1.5–2 mm

The pharaoh ant is 2 mm long and yellow. The tip of its rear body is black. 

Occurrence

The pharaoh ant comes from the tropics. It lives in places where the warmth and level of moisture remain constant, and where they have access to water and food. They are omnivores.

The species reproduces at relatively high temperatures (+18 °C). It nests in all possible cracks. The same building may have several nests.

Pharaoh ants eat various things, especially from the animal kingdom, including dead insects and other dead animals, as well as the excrement of rats and mice.

Damage

When pharaoh ants have access to electric appliances such as a television, computer or coffeemaker, they can cause it to short circuit. Pharaoh ants like warm places and are attracted by district heating channels, through which they can crawl from one apartment to another.

Prevention and extermination

The extermination of the species is often difficult and requires help from a professional exterminator. The ant nests need to be found, but they are often in a place where pesticides cannot reach them.

Identification marks

Adult: 2–4 mm

Larva: 3 mm

The common fruit fly belongs to the family of Drosophilidae. Drosophilidae flies are small, reddish-brown or black and brown flies, which often have red eyes. Common species include the vinegar fly and the fruit fly. The larva is light in colour and resembles a worm.

Occurrence

Adult fruit flies are mostly seen indoors during the late summer and autumn. The larvae feed on various rotten vegetable-based waste, especially rotten fruit. They also eat beer or wine left at the bottom of glasses, ketchup, sweet jams, rotten potatoes, cucumber, kitchen waste and vinegar.

The populations in homes may have spread from store-bought fruits that have had eggs, which the human eye cannot see. During the summer, the adult flies can fly in through the windows, or larvae can be brought in with slightly rotten berries and fruit.

Fruit flies reproduce quickly. The female may lay up to 400 eggs in foodstuffs. The larvae grow within a few days and encapsulate. Generation from an egg to an adult takes around 10 to 14 days.

Damage

Fruit fly larvae ruin the food they have contaminated. The flies also spread yeast and bacteria onto food ingredients.

Prevention and extermination

Take care that no fruits are forgotten in cupboards or on tables. Store all foodstuffs in sealed containers and empty the biowaste bin regularly.

You can trap the flying adult flies in a container which has some water and vinegar on the bottom with a drop of dishwashing liquid that helps remove the surface tension.

Identification marks

Queen: approx. 25 mm, drone: 20 mm, worker: 18 mm

There are over 10 different species of wasps in Finland. In general, they have transparent wings, horizontal stripes on the back of their body and a poisonous sting.

Occurrence

Wasps often build their round hives under eaves or in attics close to the ceiling. A wasp hive resembles paper and is usually grey. A full-size wasp hive may have thousands of individual wasps. Wasps make annual hives. Near the end of summer, wasps may also fly indoors to find food. 

Damage

Wasps use their poisonous sting to paralyse their prey and defend themselves. A wasp sting may be dangerous to a small child, someone who is allergic to wasps, or if the wasp sting is close to the mouth or throat. The stung area usually has a burning pain and swelling. A cold poultice, cortisone ointment or an anti-adder venom medicine can be applied as first aid. If you are allergic to wasps, please seek medical treatment.

Prevention and extermination

Individual wasps that have accidentally flown indoors can be exterminated with pesticide aerosols. If a hive is in a difficult location, it is best to destroy it during the evening, when the wasps have stopped flying and are all inside the hive. When destroying a hive, please ensure that you are fully protected. A hive can be cut off and dropped into a bag, which is then destroyed. The other option is to spray the hive full of pesticide aerosol through the opening at the bottom of the hive. The treatment should be carried out again the next evening to ensure that all the hive residents are exterminated.

Identification marks

Adult: 1–2 mm

Barklice are light in colour and have a delicate body. Their head is relatively large and has antennae. Species living indoors do not usually have wings. The larva is similar to the adult.

Occurrence

Most species live in the wild in a rotting tree, for example. Some species of barklice such as dustlice live in apartments, warehouses and various institutions. Barklice may also appear in new buildings 2–3 years after completion if the structures have not had time to dry completely. Barklice disappear as the structures dry out.

Barklice feed on mould fungus and vegetable and insect waste. They can also be seen in grain products. They reproduce in warm and damp spaces. If there are a large number of barklice, it may be a sign of moisture damage. They do not usually survive in dry spaces where mould forms slowly.

Damage

If dustlice are discovered in food, it is unpleasant. They do not bite humans. Barklice may cause allergies, itching and a rash for those who have become sensitive to them.

Prevention and extermination

Remove the object that attracted the insects, such as a bag of flour from a damp storeroom, or a water leakage that causes mould. You can also use pesticide aerosols that include pyrethrin or dry the area and vacuum clean it.

Centipedes and millipedes belong to the subphylum Myriapoda. Land-dwelling arthropods have many pairs of legs and several consequential segments that resemble each other. The adults and the larvae resemble each other.

Centipedes

(Chilopoda)

Identification marks

Adult: up to 30 mm

Centipedes are flat, and each of their segments has one pair of legs.

Close to apartments, the most common species is the up to 30 mm long brown centipede (Lithobius forficatus), which has 15 pairs of limbs and short antennae formed of the segments. The first pair of limbs has transformed into jaw appendages, which point to the sides and are thick and hooklike. There are claws in their tips which are connected by a duct to a venom gland.

Occurrence

Centipedes are predatory arthropods, which occasionally wander into cellars and other damp premises. They hunt for isopods, for example.

The animal’s skin is highly permeable to moisture, and centipedes are therefore sensitive to dryness. The species are mostly active during the night or at dusk or dawn, when the moisture level of the air is high. Centipedes live in the soil, rotting vegetable matter or in the cracks of tree bark.

Centipedes are often confused with millipedes (Diplopoda), which, however, are herbivorous.

Damage

Centipedes do not cause any damage. Instead, they are beneficial animals.

Millipedes

(Diplopoda)

Identification marks

Adult: 5–15 mm

Millipedes are cylindrical and have a hard surface. They have two sets of limbs on each segment of their body, and the number of limbs may vary from around twenty to over a hundred. The first set of limbs has been reduced into hooklike appendages. The antennae are short and formed out of eight segments.

Occurrence

Millipedes move quite slowly and curl up if they are bothered. Millipedes live in damp soil or in vegetation litter. They mostly feed on decomposing plant waste.

Millipedes live in large numbers in compost, for example. They can be carried into residential buildings with plotted plants, or if composted soil is used for decorative plants. Millipedes favour damp spaces and therefore usually stay in the flowerpot, although they may sometimes drop onto the floor. 

Damage

Millipedes do not cause damage, and loose insects can be put back into the flowerpot or taken outside.

Identification marks

Adult: 10–20 mm

The European earwig is shiny and dark brown. It has yellowish legs and wings. The end of its body has claw appendages, which are curved and slightly thicker in the males.

The claws of females are straighter and smaller. The European earwig has functional wings, although it rarely flies. The larva is similar to the adult but smaller in size.

Occurrence

The European earwig is an omnivorous insect. It usually moves around at night and can be found in compost and plant litter, for example. The species is attracted to shady, cool and damp spaces. They can often be found underneath various objects and baseboards. The European earwig feeds on insects, their eggs and plant parts.

Damage

As an omnivorous species, the European earwig is useful to humans, as it preys on plant pests, but it may sometimes gnaw on the buds of decorative flowers. For example, the European earwig eats leaf vegetables, cabbages, root vegetables, cucumber, fruit, and with regard to decorative flowers, dahlias, dianthus, zinnias and roses, in particular.

The European earwig crawls indoors during the autumn especially to look for cover.

Prevention and extermination

You can try to prevent European earwigs coming indoors by placing a solution that dries up the insects, such as stone dust, burnt lime and diatomaceous earth, on suitable spots in the bathroom, as well as on doorframes and thresholds.