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Your Guide to Hornets


With summer around the corner you might be just a little apprehensive about what to do with the accompanying increase in insects, especially the stinging kind, and more especially hornets. Expect to see hornets from around the beginning of May until the end of September, although they have been known to hang around until late October and November, when the time of working is over and they can party on rotting apples. The fermenting apples go straight to their little heads and they fall to the ground in drunken bliss.

About hornets

Hornets are part of the wasp family (Vespidae). They are the largest and most aggressive members of the group. There are many different types of hornets; the type most common in the UK is known as the Vespa Crabro, or what the Americans call the European hornet and measures between 2cm and 3.5cm. Larger and fatter than the common wasp, hornets have a chestnut-brown and yellow colouration. They’re known to pack a powerful sting because their poison sac can carry a lot more venom than bees or wasps.

Black hornets or bald-faced hornets are common in North America. The Asian giant hornet, including the Japanese giant hornet (Vespa mandarinia or yak-killer hornet), is the largest of the hornet species and is native to temperate and tropical Eastern Asia. Giant hornets have a wingspan measuring 7.6cm and a body length of 5cm.

The crabro is the least aggressive of the hornet species and has a reputation of preferring to bite rather than sting humans, even when cornered. The venom of some hornet stings, such as that of the Asian giant hornet, is particularly painful because it contains a large volume of acetylcholine.

Closely related to the yellow jacket wasp, hornets normally prey on insects and caterpillars, including many species considered pests by man, like aphids. Both adults and larvae eat mainly insects, but their diet also includes spiders, tree sap and windfall fruit.

Hornets have the most fearsome reputation among stinging creatures, and it’s largely because of the pain caused. They are only aggressive when there’s an obstacle in their flight path or sudden swift movement anywhere near them, especially when in close proximity to their nests. However, hornets more difficult to control than bees and wasps because they fly at night and will fly towards light. So if you have an outside light and a nest somewhere in your garden chances are good that you’ll encounter a hornet or two when you’re returning from an evening out.

Hornets nests and life-cycle

The hornet queens, having hatched and mated at the end of the previous summer, survive the winter by sheltering in rotten wood or soil cavities. Their bodies produce glycerol which slows their metabolism right down and keeps them from freezing during the cold winter months. As the weather warms and spring approaches, the hornet queens emerge from hibernation and search for suitable nesting grounds and food.

Once the queen has found the perfect location to build a nest, she makes a small stalk (pedicel) which is the backbone structure of the nest. She begins building the nest outwardly in cell-shaped cavities in which she lays her eggs. The nest looks like large inverted tear-shaped ball with a single opening near the bottom.

Within a week the larvae begin developing, and continue to develop through five larval stages over the following two weeks. The larvae are initially kept in the cells by a sticky secretion but as they grow their bulk keeps them snugly secured. They produce a silken thread which covers the cell and acts as a protective sheaf for the pupae metamorphose.

Once metamorphosis has been completed, the hornets bite their way out of the cell. The newly hatched worker (vexator) doesn’t immediately exit the cell, but stays on to help care for developing larvae by increasing the temperature in the nest. They will stay in the nest for two or three days before they start foraging for food.  It is at this point that the ‘paper sleeve’ is started which will cover and protect the cells.

Vexators don’t aid in nest building at this point; instead mature female workers who fly out to forage for food and construction materials are responsible for nest building.

During this period the queen continues to fly out of the nest foraging for food but as soon as there are around five to ten female workers, her flights away from the nest decrease, and the female workers take over the role of foraging. The workers’ life cycle is very short, between three and four weeks. As the season progresses, the queen stops leaving the nest and remains behind to lay and fertilise eggs to increase the nest population. Towards the middle of summer, males and females hatch and mate, becoming the next generation of hornets. The old queen, workers and males die.

Hornets’ stingers

The sting is a lance-like hollow tube that goes backwards and forwards in a sawing motion, forwards to penetrate deeper into the flesh and backwards to return to the abdomen and poison sac to collect more venom. The hornet is able to keep stinging until its poison sac is empty, and the rapidity of the sawing action is phenomenal. The supply of venom in the poison sac is around 50mg and typically each sting uses 10-15mg of venom, so a victim of an angry hornet can expect to be stung up to 5 times within the space of 0.3 seconds.

However, as a general rule, a hornet uses its venom sparingly, so once the hornet has given a first sting it tends to fly away rather than sting you repeatedly. It’s thought that this is because the venom is used to paralyse the hornet’s prey, so unless the hornet feels under siege or senses a threat to the nest it prefers to reserve poison for its prey.

As the poison penetrates your body, your immune system produces antibodies which attach to the antigen to neutralise it, and in some cases the result feels like an allergy, which includes symptoms, like wheezing, sneezing, runny eyes and itching.  Typically, these allergic reactions are not too severe and are more painfully annoying than anything else. However, in a sensitive person, the condition can become fatal if anaphylactic shock, a life-threatening allergic reaction characterised by swelling of body tissues and a sudden drop in blood pressure, occurs. People have difficulty breathing and it’s this which could lead to death.

Given all this, you’ll see why it is vitally important that you treat hornets with all due respect, and never attempt to move or destroy their nests without professional guidance and assistance.

How to treat a hornet sting

If the hornet has left its stinger in your flesh, remove it with some tweezers and wash the area with soap and water. Emma Lloyd recommends applying a small amount of meat tenderiser to the wound as it contains certain components that can break down the venom and may relieve the pain to a certain degree. You can also alternate putting on and taking off an ice pack every ten minutes and take an antihistamine tablet or apply some antihistamine ointment to the wound to relieve itching.

Though rare, infections can set in so watch for swelling, continued pain and redness and get medical attention immediately if you think the sting is becoming infected. You also need to watch out for an allergic reaction because this is where the situation can become life-threatening. If you experience difficulty breathing (wheezing or shortness of breath), facial swelling, tightness in your throat, or feel weak or faint, or a decreased level of alertness or consciousness, then you’re bordering on anaphylactic shock and must get medical treatment ASAP.

Getting rid of hornets

If one hornet feels it’s in danger or that the nest is under threat, it will release a pheromone that alerts the rest of the nest. The hornets in the nest prepare to respond to the threat with extreme prejudice. One nest typically contains 5,000 hornets, and even the healthiest, most robust person on the planet can’t withstand up to five stings from 5000 angry wasps.

Some websites advise that it is possible – although we don’t recommend it – to get rid of a hornets nest yourself, provided it’s still in the very early setting up stages, by knocking the nest off its support and aiming to flatten the nest to kill or discourage all hornets.  That means while it’s much smaller than a tennis ball and while it’s relatively cool in early spring.  Do not attempt to remove a nest on your own when it’s fully constructed or in summer at its peak.

You can also use special insecticide spray – jet spray for extra distance and force. Spray the nest late at night when most of the swarm will be asleep. If you need to use a torch to see what you’re doing, put on a red filter, as hornets are attracted to standard light but not red light. Once you’ve thoroughly sprayed the nest, walk away as calmly but quickly as possible to get out of the line of fire. Always wear long trousers (jeans), closed shoes, long-sleeve shirts and/or a thick jacket, thick rubber gloves and goggles if possible

If you do cross a hornet’s path, remember at all times to slowly move out of its way to avoid a direct confrontation. Try to move as far away as possible so that you increase the distance between you and its nest.

A far safer option for all concerned is to call a pest control company that specialises in hornets, wasps and other stinging insects. There are plenty of companies that use humane nest removal techniques, so your conscience can stay clear. Don’t forget to let your home emergency insurance provider know about the problem, so you can make a claim.