The hymenoptera include ants, wasps and bees. They, like beetles, moths and flies, have complete metamorphosis. The larvae are limbless, blind and pale maggots. There are two pairs of transparent flying wings with relatively few but clear ribs. The rear wings are always smaller than the front wings. Mouth parts are arranged to either suck or bite. In most species, there is a clearly marked narrowing between the first abdomen joint and the following joints. In the rear, the females have a stinger, which for some is used for egg production and for others to sting.

The social hymenoptera, which have the most impact in foods in this country, form communities. The communities share hives, nests and colonies and are composed of males, queens and workers. The workers, which are the most numerous, are small females with undeveloped reproductive organs.

Solitary bees

In Denmark, there are a few hundred species of the so-called solitary bees. It is usually small, grayish or dark species. Most look like small versions of the honeybee. They are called solitary bees because they do not live in the colonies. Each female bee builds its own nest, lay eggs and gather food for the larvae by herself. Depending on the species, solitary bees can build nests in the ground, in plant stems, in holes in walls or in woodwork, and the nests can be built from different materials such as clay or plant parts.

When feeding the larvae, the bee fills the nest cells with pollen and nectar.

Solitary bees play a role in the pollination of many plants. They can sting, but they are not very aggressive, and since they do not have to defend a shared nest, there are no cases of mass attacks. Because solitary bees are often small, the stings are usually mild.

The Colletes davieseanus is a solitary bee that often lives in colonies. It can dig passageways to the nests in the loose mortar of houses. It rarely stings, but it can destroy the mortar.


In most cases, having a bumble bee family in the house poses no problems. They are, as mentioned, peaceful, and they make themselves useful by pollinating crops in the garden. In the rare cases when they are not tolerated, they can be controlled in the same manner as honeybees.

Bumblebee stings

Most bumblebees are so good-natured that people think they cannot sting. This is, however, not the case. Bumblebees have a powerful stinger and venom glands. By virtue of their size, the sting is painful.


High season for bumblebee

Fig. 47. There interest in bees (Fig. 46) and bumblebees peak during the in the hottest time of the year.



In Denmark, there is a dozen species of the usually big, strong and furry bumblebees of the genus Bombus. In contrast to honey bees bumble bee colonies only live one season. In the autumn all the workers and the old queen die. There are some young queens who – after having mated – goes into hibernation and thereby saving the family through the cold period. Early the next spring, they come out and find suitable places to establish new colonies.

Most bumble bees construct their nests in the ground, in an abandoned mouse nest or between stones in a stone wall. An empty nesting box for titmice, a cavity wall, a crawl space or an insulation mat in an attic are also good places for a bumblebee nest. The nest is lined with vegetable fibers, moss or hair, and the workers build brownish wax pots used to store eggs and food supplies. The colonies are not very large – and often consist of a maximum of 400-500 members.

Bee stings

honey bees in July

Fig. 46. Peak season honey bees

Honeybees only sting in defense. The sting is barbed and is, along with the venom sac, modified so it stays in the victim. The bee dies afterwards, but the sting can continue to deliver venom.

There is about 0.1 mg venom in one bee sting, and in order for the effect of the venom to be dangerous for an adult human, it probably takes 2000-3000 simultaneous stings. Cases of deaths after bee stings are practically always caused by hypersensitive reactions to one or more of the proteins in the venom, or stings in the throat, which may cause choking.

Bee and hornet venom is similar in composition and effect to snake venom, but the allergens in them are not the same. The species of honey bees that live in Denmark have been kept as livestock through many generations, and through breeding they have become extremely peaceful. The notorious “killer bees” (Africanized honey bees) are a crossing between European bees and an African species that was bred in South America in order to have a more sturdy and active bee. Unfortunately, they are also very aggressive and difficult to deal with, but stories that they seek out and attack animals and humans are exaggerated.

What to do about the sting? The stinger should be removed, but carefully to avoid pressing more venom out of the poison sac. This can be done by scraping it off with a pocket knife.

Bee stings hurt, but usually do not entail complications. There are hardly any of the household remedies: ammonia solutions, sugar, sucking out the venom, plantain leaves, etc., which have more than a psychological effect. Whatever you do, you should keep an eye on the person who has been stung. Is there imminent dizziness or nausea, you should seek medical attention. The same applies to stings in the mouth or throat, since they can lead to swelling that can cause breathing difficulties.

People, who have developed such a degree of hypersensitivity to the bee venom that a single sting can be life threatening, can be treated preventively with vaccines. The treatment is lengthy, so it is necessary to start the treatment well before the bee season starts.

The honey bee

Honey bee

Honey bee

Almost all honey bees, Apis mellifica, live as livestock in designated hives, however, wild swarms can settle and adapt in cavity walls, chimneys or hollow trees.

Solitary bees

There are about 200 different species of solitary bees in northern Europe. Although they may live gregariously, e.g. Colletes daviesanus (see p. 157), they are known as solitary bees because each individual female makes her own nest, lays and tends her eggs and collects her own food.

According to the species, solitary bees may construct their nests in the ground, in plant stems, in timber, or in buildings where crevices in masonry and woodwork offer good shelter. The nests may be built of various types of material, such as mud, plant material, or of substances produced by the bees themselves. The females fill the larval cells with pollen and nectar.


( Latin: Superfamily Apoidea)


Davies’s Colletes

( Latin: Colletes daviesanus)

These are solitary bees (p. 180) which do not form true colonies although several may live close together. Like other bees they have a sting, but are not very aggressive. In the wild they live in chalk or clay, but they may also live in mortar if it is not too hard.

These bees dig cylindrical, horizontal tunnels in the mortar, but do not enter cavity walls. They nearly always choose a sunny aspect, and on the whole they are most active when the sun is shining. The diameter of the tunnels is about the same as a pencil and they are lined with a very fine, transparent material which is secreted by the bee’s salivary glands. Each individual cell is 1 cm long and it is filled with a mixture of pollen and nectar. When it has been completed the bee lays an egg in it, seals it with a lid and starts on the next cell in the series. Normally there are

2-8 cells in each tunnel. The larvae which hatch from the eggs feed on the stored food, overwinter in the cell, pupate in the following spring and emerge as adult bees, usually in early July.

In normal circumstances the damage done by these bees is fairly restricted, but it can be annoying when plaster is being gnawed out the whole time, and in a serious attack when much mortar is being removed it may be necessary to take countermeasures.

Outside the period when the bees are flying (mid-June to mid-August) this can be done by simply scraping out the loose mortar together with the bee cells and larvae. If this is carefully replaced with a strong mortar containing cement it will not matter if some of the cells are still in place as any bees that emerge later will not be able to reach the surface.

On the other hand, if repair work has to be done during the period when the bees are on the wing they will need to be dealt with first otherwise they will be able to dig new holes before the mortar has hardened. Dusting the affected areas of wall with an insecticidal powder will usually solve the problem.

It should be remembered that even though the bees living in the mortar have been killed off there will always be a risk of a new attack so long as there are still areas of wall with loose mortar.

Now and again woodpeckers find out that there are fat, juicy bee larvae in the wall. Once they have learned the trick they will arrive and hack great craters in the mortar in order to get at the grubs. If one cannot tolerate this form of biological control it will be necessary to scrape out the larvae and make good the mortar.

Sparrows and tits often climb around walls searching for insects and spiders which they pull out of holes and crevices. Normally they do no damage to the wall, but sparrows and pigeons may peck lime out of the mortar and in some cases damage the bricks.

The larvae of dermestid beetles frequently gnaw their way into a variety of materials when they are about to pupate. It is rare for them to bore into plaster but they occasionally do so.

Glass wool used for insulation might not appear to be a very suitable material for nests but in spite of this, mice and rats will gnaw tunnels through it and construct their nests in it, thus reducing its effectiveness as an insulator.

Bumble bees may also establish them- selves in insulating material, but the damage done will be local and not very serious.

When tufts of insulating material appear under the eaves it will normally be due to sparrows or starlings that have pulled it out to make a place for their nests.