WASPS
Wasps
Background: We know them as hornets, yellowjackets, and wasps - although there are some 75,000 different species of wasp. They comprise the family Vespidae and belong to the order of insects called Hymenoptera. There are several species of true wasps found in Europe, the two most often found are the Common Wasp (Vespula vulgaris) and German Wasp (Vespula germanica).
The largest European social wasp, usually 30-40 mm long, is the hornet (Vespula crabro). This large and impressive insect does occurs in Britain, but is relatively uncommon and largely confined to the south. They are usually non-aggressive.
Tree wasps (Dolichovespula sylvestris), red wasps (Vespula rufa) and the cuckoo wasp (Vespula austriaca) are also sometimes encountered. In Scotland, the Norwegian wasp (Vespula norwegica) is most abundant. They all look distinctively wasp-like, and telling them apart is often a job for the expert.
Although Wasps are quite useful insects, helping to control other pests, clearing dead insect debris and cross pollinating plant life in general, they are regarded as pests and a threat to health. They are regarded as a nuisance during the summer when workers go about the business of collecting food for young wasps and can indulge their passion for sweet foods e.g. jams and syrups
There are seven species of social wasp. The commonest is the Common Wasp Vespula vulgaris followed by the German Wasp Vespula germanica, both of which nest underground and in cavities in trees, walls and buildings. The Tree Wasp Dolichovespula sylvestris is locally common and very aggressive and builds its nest in trees and other aerial sites as well as underground. The Norwegian Wasp Dolichovespula norwegica is less common in the southern half of Britain but is the dominant species in Scotland. It builds its nest among twigs and branches. The Cuckoo Wasp Vespula austriaca does not have workers of its own and lays its eggs in the nest of another species - the Red Wasp Vespula rufa - which nests underground. The largest - the Hornet Vespa crabro - is a southern species which nests in hollow trees or in buildings. The differences between them are subtle but they all have similar black and yellow markings and THEY ALL STING!
Colonies: Wasp workers will aggressively defend the nest by stinging anything causing a disturbance. The sting is caused by the injection of venom into the victim by means of the modified ovipositor (egg laying tube) of the females.
Unlike bees, wasps are able to sting repeatedly. A wasp can withdraw its sting from the victim, a bee cannot.
Nests: The queen builds the nest as a suspended ball. A well established colony of paper wasps can have two hundred or more individuals living on a nest the size of a man's outstretched hand. An underground yellowjacket nest, on the other hand, can be the size of a beer barrel and sometimes larger. A nest of this size can have five thousand or more hot tempered, stinging insects. Social wasps use paper (wood pulp) to construct their nests. The process is simple....... a wasp collects wood fiber by using its mandibles (mouth parts) to scrape it from worn and weathered wooden fences, buildings, telephone poles, and other sources. Sometimes it collects fiber from man-made paper products such as paper bags or cardboard boxes. The insect then chews the wood and mixes it with saliva. This makes the wood fiber extremely soft and moist. After a period of chewing, the wasp adds the paste to the nest structure and spreads it out with her mandibles and legs. After it thoroughly dries; a type of tough, durable paper is formed.
Description: The common wasp grows up to 19mm long. Their eyes are kidney shaped, they have a yellow head with a black top, a black thorax with yellow on its sides, a yellow abdomen with black bands, black antennae and yellow legs. They have two pairs of wings, the hind wings are smaller than the forewings and are linked by a row of hooklets. The hind wings are usually hidden beneath the front pair and, when at rest, the wings are folded longitudinally in the manner of a fan.. The mouth parts are adapted for chewing and licking. They can easily be distinguished from mining bees because of their pointed body and waist.
Fairly long, thick antennae. There are 12 segments in the female and 13 in the male.
These insects are common throughout Europe and are found in gardens, woodland and meadows. They are omnivorous, feeding on fallen fruit, nectar and carrion, but mostly catching other insects.
Some species of these are up to 30mm in length.
Bees can be told apart from wasps by the lack of conspicuous yellow bands, and they are much furrier than wasps. Also, they often have little yellow pollen sacs on their strong hind legs.
If you find a very large wasp with a long sting, and no wasp waist, it is a giant wood wasp (Urocerus gigas) female. The males lack the sting, which is actually for egg laying. They are harmless.
Hoverflies (Melauostoma species, for example) have yellow and black banding and are wasp sized - they mimic wasps and bees. You can recognise them by their distinctive hovering, darting flight. Being flies, they have only one pair of wings. Some species are extremely useful predators of garden pests. Others scavenge dead material.
The bright yellow and black striping of wasps is a warning pattern to prospective predators, such as birds, that the insect is venomous and best left alone. This yellow and black colouring is copied, as a form of mimicry, by many insects, which in reality are perfectly harmless and merely take advantage of the deterrent effect of appearing 'wasp-like'
Biology: Most members of the Vespidae have a worker caste and form annual colonies which last for just one summer.
Wasp colonies have a distinct caste system. It includes:
There are four stages to the life cycle of
wasps:- eggs are laid in the first tier of the nest built by the Queen. They are
cemented into place and the emerging larvae, which hatch in a few days, only
partly emerge so as not to be too far from the cell. When fully grown they
cocoon themselves within the cell in order to pupate, 6 weeks after the eggs are
laid the first generation of worker wasps emerge.
The worker wasps will be males and females, though these females are unable to
reproduce. During the late summer however, eggs laid will produce fertile
females. These will mate and will be the only wasps that hibernate over winter
to be next year's Queens. This year's Queen and all the workers will die with
the onset of colder weather.
Wasps have a life cycle which has four stages:
All wasps over winter as Queens, usually hibernating in buildings, underground or under bark or in tree cavities. The young Queen emerges from hibernation in Spring, feeding on nectar and sap and begins to construct her new nest from wasp paper, a mixture that she concocts from chewed wood, plant debris and saliva. Nests are often found in holes in the ground, hollow trees, eaves, attics, or garden sheds. A new nest is always built from scratch. Old nests are never returned to although they are sometimes built in the vicinity of old nests.
Within each of the hibernating Queen wasps is a tightly packed ball of dormant sperm stored from mating the previous summer. She is able to release newly activated sperm each time she lays an egg without the need for repeated matings. A Queen wasp can lay as many as 2,000 eggs each day therefore, each dormant Queen literally has the potential to form a new colony within weeks. Within her new nest the Queen lays her first batch of eggs, the larva construct silk cocoons in which they pupate. The larva feed on insects such as caterpillars, spiders and aphids which the wasps capture and paralyse with their sting. The immobilised prey is carried back to the nest, chewed and then regurgitated to feed the developing wasp grubs.
Between 4-6 weeks later, the first worker wasps appear which are sterile. The workers then take over the ongoing nest construction, enveloping the whole nest in wasp paper which could by now extend to 8 tiers. They also forage for food, ventilate the nest by vibrating their wings and nurture and feed the developing wasp larvae. At the end of the summer the Queen lays eggs which produce Drones. By the end of the summer a nest may house over 20,000 wasps. Common wasps do not have a mating flight like ants do. Mating takes place between young Queens and drones in the vicinity of the nest. The male wasps fertilise new Queens who go on to search for hibernation sites. The remaining wasps die as the weather becomes colder, nests are then deserted and can be safely broken up or removed.. It is not uncommon to discover a hibernating queen in the folds of curtains in houses.
The number of wasps in the late summer/autumn depends on two things.
A bad spring will mean that many nests are destroyed so fewer wasps are produced.
A large number of females overwintering will mean more competition for nest sites etc. in spring so the surviving queens will be in poorer condition and therefore fewer offspring will be produced.
The best conditions for numbers are therefore a dry spring and fewer overwintering females. The colonies will then be successful, producing many offspring and many overwintering females.
The following year, however, should see lower numbers because of the competition from many overwintering females.
Left alone, wasps are not normally aggressive. However, they become more aggressive as a result of crowding and temperature.
The temperature of a wasp's nest is 5 - 10oC above outside temperature. With outside temperatures in the high 80s - 90s the temperature inside a wasp nest can be very high indeed.
Overcrowding or high populations can lead to aggressive behaviour both in wasps and Man therefore any slight irritation could cause an aggressive response.
The sting is the object of our fear of wasps. Unlike that of the bee, the wasp sting has no barbs and can be used many times. The sting is, in fact, a modified ovipositor and therefore the male wasps are unable to sting. Then pain of the sting is caused by a complex protein injected through the needle-like sting as it penetrates the skin. Individuals react differently: some are hardly affected, others may suffer pain and swelling while in other, rare cases, individuals may suffer serious allergic reactions which may result in death from anaphylactic shock.
Cures for wasp stings are many. Here are a few from the 15th century:
A plaster of wild mallow leaves
Oil of bay
Vinegar and salt tempered with honey
Goose dungContrary to popular belief a wasp sting is neutral NOT alkaline with a pH of 6.8 to 6.9 therefore the application of an alkali will do no good.
The important thing is to:
Wasps can cause serious damage to soft fruit but ripening apples and pears are unlikely to be affected unless first damaged by birds or caterpillars. Wasps can be a considerable pest in sugar warehouses, jam factories and other sites containing sweet-smelling substances. They are a nuisance in houses where food is being cooked or eaten. They are also a serious pest of hive bees in some seasons. In the spring workers will attack and carry off foraging worker bees while later in the year they will take honey and carry off bee grubs and pupae.
Hornets are part of the wasp family, and their life cycle is very much the same.
Habits: Nest construction begins in earnest around June with the nest reaching its maximum size in September.
Unlike honeybees, wasps do not swarm
Workers are smaller than queens and never lay fertilised eggs
Wasps will sting many times when aroused
Workers will travel up to 500 metres from the nest in search of food.
Wasps can sting and will defend their nests with vigour. However, wasps are beneficial to gardeners - one worker wasp can collect over 100 aphids in one day.
The needle-like sting is concealed near the tip of the abdomen. It is a modified ovipositor and is therefore only possessed by the female - male wasps do not sting.
Health Risks - Pest Status: Although Wasps are quite useful insects, helping to control other pests, clearing dead insect debris and cross pollinating plant life in general, they are regarded as pests and a threat to health. During spring and early summer, wasps can be regarded as beneficial, as their larvae are fed on other insect pests. Later in the season, as larval rearing is reduced, the workers search for sweet substances. They can damage ripened fruit and are a nuisance when attracted to sweet food. Wasps attack plums, nectarines, late strawberries and grapes. The sweetest varieties seem to suffer most. Hard fruits like apples and pears are attacked only if previously damaged by birds etc. Occasionally wasps damage dahlias, rasping away the succulent stem and leaf stalk tissue, apparently to get water, as the rasped material is often not removed. Common wasps have been observed invading honey bee hives and nests to steal their honey although usually the bees are able to defend themselves.
Stinging is an excellent defense in wasp colonies against predators and other possible dangers which present a threat to the nests and their occupants. A stinger is actually a modified egg-laying tube which is connected to a venom sac inside the insect's body. A wasp is quite capable of stinging repeatedly because it can easily withdraw its stinger from the entry point. When a wasp wants to sting, it curves its abdomen downward and punctures the victim's skin with its sharp stinger. Muscles then drive the stinger deeper into the flesh. Meanwhile, venom is being pumped from the venom sac, through the stinger, and into the wound. It is similar to how a hypodermic needle works. Chemicals in the venom cause the pain and irritation from the sting. Wasp stings may be unpleasant to most of us, but to some people they can prove fatal. The ability of these social insects to inflict multiple stings means for certain individuals they can kill. The real bad news for the allergic is that stinging wasps are virtually everywhere.
Health Risks - Medical Situations: The female wasps can produce a painful sting which can be treated with a cold compress and antihistamine creams applied within 20 minutes of the stinging incident. Very occasionally, the sting may cause anaphylactic shock. Anaphylaxis also known as anaphylactic shock is a severe and potentially a fatal allergic reaction. The whole body can be affected, usually within minutes of exposure to the allergen but sometimes after several hours. Symptoms of this include a sudden drop in blood pressure and narrowing of the airways causing difficulty breathing, faintness, a rash, swelling of the face and vomiting with abdominal pain or diarrhoea. Immediate medical assistance should be sought if anaphylactic shock is suspected. Wasp stings around the throat can be particularly dangerous and can lead to respiratory obstruction which may cause faintness or vomiting.
Health Risks - Domestic Situations: Wasps are social insects, forming colonies inside nests specially constructed in soil banks, roof spaces, garden sheds, and in cavities in trees and walls. They are, therefore, frequently associated with domestic housing. It should only be necessary to treat wasps nests if they pose a particular danger to you. Unless such a danger exists, the nest should be left undisturbed.
They may carry disease picked up during their visits to dustbins, bottle banks and carcasses and can contaminate food if allowed to settle on it. It is usually the late summer when the workers do not have to feed the larvae with high protein foods that they can indulge in sweet substances - fruit, jams, syrups etc. They enter kitchens in search of sweet food, and while not particularly hostile, they will sting if aggravated. As the cooler weather arrives, the wasps become more irritable, and this is not helped by them feeding on over-ripe fruit, giving them the appearance of being "tipsy". Again they are better left alone when in this condition as they are prone to stinging when in this state.
Control - Although wasps are troublesome to us it would be unwise to destroy nests without good reason. If you feel wasps are doing significant damage to wooden garden structures, the best remedy is to apply a wood preservative. This will damage plants if it touches them, so it is best to apply it during winter. Wasps are controllers of far more injurious pests of forestry, agriculture and gardens. Killing individual wasps will have no effect on the overall population of the nest. If the presence of a nest is causing no direct problems, then it is best left well alone. The venom of the wasp contains a pheromone which acts as an alarm causing other wasps to become more aggressive when a wasp has stung something or has been killed itself. So it is a bad idea to swat a wasp near its nest site or to attempt to remove the nest yourself.
Nests are usually greyish or yellowish in appearance. In the early stages of nest building, when the nest is about the size of a golf ball it may be possible to knockdown the nest and dispose of it by burning it. However, as the nest develops the most effective control of wasps is by the use of insecticide dust to the nest itself. By late summer, as the colony grows, the nest may reach the size of a football or even larger. The whole structure is usually suspended from an overhead support or from the ceiling of the nest cavity on a stout 'paper' stalk, with an entrance hole at the bottom.
The destruction of a nest is achieved by applying an insecticide directly onto the nest or at the nest entrance. In this way the insecticide is carried into the core of the nest by the wasps, eradication follows within a couple of days after treatment. Pest control operatives may be equipped with lances, several feet in length in order to access out of reach nests. These lances are capable of firing insecticide into the nest, under the driving force of compressed carbon dioxide. The alternative treatment is to Surface spray an insecticide directly onto the nest. Nests should be treated late in the day when the nest is at its quietest. Wasps will attack at the slightest provocation so care should be taken to avoid disturbance to the nest.
Commercially available insecticides are mostly carbamates, a form of nerve toxin, these are quite residual and normally not available to the public. Pest control operatives may also have access to rapid knockdown liquid insecticides which are quite expensive but very effective, again not normally available to the public. The use of insecticide is carefully controlled by the Control of Pesticide Regulations 1986. The pest control operative will need to be fully trained and all necessary measures taken to comply with the Health and Safety at Work Etc. Act 1974.
Resources - Please contact the Environmental Health Department at your local council or a reputable pest control company for suitable pest control measures.
By Gareth Evans - Ivytag