In a very coarse way, many different species of spine hymenoptera are often referred to as wasps, which have the characteristic of being able to inflict painful stings on people.
However, it is good to learn to recognize and distinguish species of hymenoptera because not all of them are dangerous in the same way and some species are even useful and fundamental for the ecosystem and the environment.
For example, bees and other useful pollinating insects such as bumble bees have a body completely covered with hair on their legs, abdomen and chest, unlike wasps which have a glabrous, apparently smooth body.
The wasps then have the typical narrow waist, commonly known as “wasp waist”, and are often active also at night unlike bees.
Finally, wasps can sting repeatedly, unlike bees, but by stinging they lose the sting together with a part of the viscera and therefore they die. For this reason it is much more likely to be stung by a wasp than by a bee, as the latter only attacks for extreme defence.
The most dangerous of the stinging insects is certainly the bumblebee (Vespa crabro). The sting by this insect is very risky and in case of multiple stings (attack by a disturbed swarm) can represent a serious risk to life itself.
Despite the buzzing of its flight it is not the most aggressive among hymenoptera and usually does not sting if it is not harassed. Unlike other hymenoptera that do not fly in the dark, bumblebees maintain partial activity at night.
The bumblebee is the largest hymenoptera in Europe. It is usually 30-35 mm long, the sting reaches 3 mm in length. It is a predator and attacks almost all species of insects, including bees.
The bumblebee can sting repeatedly. Like other wasps it is attracted by sugary foods, such as ripe fruit, and meat, such as ham.
The bumblebee, which has a reddish brown colour and an orange-yellow abdomen, is often confused with the cartoon bee (Xylocopa violacea), a kind of solitary bee with a strong buzzing sound 21-24 mm long and which feeds exclusively on pollen and nectar, making it a useful pollinator.
The common wasps (Vespula (Paravespula) vulgaris L.) have four yellow spots on the back of the thorax and an anchor mark on the “snout” (clypeus) which distinguishes them from the other wasp, or yellowish (Vespula germanica F.), equally widespread, and both species are 10-20 mm long.
These social wasps, which include the common garden species, live in annual colonies, each one founded led by only one queen and thousands of smaller workers (up to 3000 specimens in autumn for the V. germanica) bred in paper nests which can measure 20-30 cm of diameter (smaller those of the V. vulgaris).
Their abdomen, trunk at the point of intersection with the thorax, distinguishes them from the polystenes (cartoon wasp) which have a spindle-shaped abdomen. The males, which are distinguished by their long antennae, appear in summer.
The larvae are fed with chewed insects or other animal material; the prey is not stung because the sting only has a defensive function.
Only the queens, recently coupled, survive the winter, often hibernating in the hive.
If they are molested, and this may happen inadvertently, they defend themselves by attacking in swarms. They are predators and capture other insects. They are also attracted by sugary foods, such as nectar and ripe fruits, but also waste soiled with jams and sweets.
The polistenes (among the most common species are Polistes gallicus and Polistes nimpha), are called cartoon wasps because the queen builds a paper nest that she makes by chewing wood, mixing it with her own saliva.
The nest, supported by a short pedestal or peduncle, appears completely open, with the cells visible, under the canopies, gutters and protected walls or branches.
They have a hairless and tapered body. They are about 12-13 mm long and fly keeping the legs very wide.
The wasp potter’s wasp (the most common species is Sceliphron destillatorium Ill.), 15-30 mm long, is a solitary species that frequently enters houses from June to August-September hunting spiders and looking for dry places to build its unmistakable nest consisting of a mixture of earth and clay, mixed with water and saliva. Inside you can see several rooms filled with paralyzed spiders at the expense of which only one larva develops. It is not aggressive and when it enters the house it can be pushed towards where it entered with a rigid cardboard.
The common bee (Apis mellifera L.), is a domestic animal species bred for the production of honey, and is considered an indispensable insect for pollination and therefore also protected by specific legislation. The bee can have a yellowish hairy body. It has very wide hind legs fringed by strong hairs that form the pollen basket and is 12-20 mm long.
In the bee society a fertile female (queen bee) governs each colony. Queens do nothing but lay their eggs and except in mating flights, they are always surrounded by worker bees.
The new queens are bred when the existing one is aging or when the population exceeds the individuals that the nest can contain, when this happens, the old queen flies away with a swarm of bees to found elsewhere a new colony.
It is on such occasions that they can also arrive in gardens in urban centres. When the swarming queen sets down, the workers who accompany her cover her to protect her, forming clusters of even tens of thousands of bees.
If the queen bee has set down just to rest, within a few hours the swarm starts again, if it has set down because it has found the site where to found the colony, the workers begin to make wax combs to contain the honey and the cells where the new workers will grow.
Also the bumblebees are vulgarly called “bumblebees”, but belong to the family of the bees, in fact, they are big bees (20-30 mm), very hairy, usually black with light stripes (yellow or white).
They live in small groups of about one hundred specimens or little more.
They live in annual colonies like the social wasps, with the first mating queens survived the winter to start new colonies in spring.
Most build grass or moss nests, above or below ground, often using old mouse holes. Inside the nests they make simple wax cells, where they breed larvae with pollen and honey.
Bumblebee workers are very small and fly so full of honey that they have to fight with the air to stay in the air. They are not particularly aggressive and never attack first and are easily seen on flowers in gardens.
They are therefore very useful pollinating pollinating insects that deserve not to be disturbed in their work.
Signs of wasp presence
Sightings or the discovery of live or dead wasps are the inevitable sign of their presence in an area.
Usually the nests are never far from where the adult individuals are, although they can be well hidden.
The nests of bumblebees reach considerable dimensions (even half a square meter have been found; a medium-sized nest has about 5,000 cells).
Both the cardboard wasps and the bumblebees build their nests by kneading the cellulose obtained by chewing wood. Bees, on the other hand, process wax nests that are therefore easily recognizable compared to those of other hymenoptera. Finally, the wasp potteries make nests in the shape of gooseberries kneaded with earth, clay, water and mud.
In its interior you can see several rooms filled with paralyzed spiders at the expense of which only one larva develops.
Environments favorable to wasps
Attics, gutters, shutter boxes, abandoned chimneys and chimneys, dry logs and/or cables are the favourite homes of these insects.
Vespulae, on the other hand, nest on the ground, in cracks in the ground or in abandoned burrows of mammals (moles, voles, etc.), until they penetrate under the roots of the plants and build their nest by hanging it from the peduncles of the root.
Bumblebees also very often nest on the ground in burrows left by other animals.
How do the wasps get into the house?
The entrance of wasps and other spitting hymenoptera into the house is almost always accidental and can become all the more frequent the closer the nests are found.
They are usually attracted by sugary food material but also by protein in the case of wasps.
The situation can become critical if you find yourself having to deal with the presence of nests inside the home or very close to them as in gardens.
Remember that when it comes to the presence of bees it is necessary to contact a beekeeper to try to recover the swarm. In other cases it is necessary to treat and remove the hymenoptera nest.
Always with regard to the presence in internal rooms, it must be considered that the intervention of the fire brigade in case of presence of acute hymenoptera is only possible in public structures or places such as schools, hospitals, public roads and where there is an immediate danger for people.
Health risks from wasps
Potentially these insects are all capable of stinging people and pets. However, bumblebees and wasps can pose a serious risk in case of swarm attacks that can inflict many stings at once.
Other hymenoptera are much less dangerous in this respect as they are almost always attacks by individuals.
Hymenoptera stings are very painful and cause a typical localized reaction. In people who are known to be allergic to these stings, especially in the case of multiple attacks, it is necessary to intervene early with drug therapy and a visit to the emergency room because the risk of a shock reaction is high and can be fatal.
Prevention of wasp infestations
Obviously the application of mosquito nets and curtains on doors and windows is a useful system to prevent the entry of these insects into homes.
In the outdoor environment, care should be taken to avoid the presence of substances that can attract wasps such as food residues including rotting fruit on garden trees.
At the beginning of spring it is also useful to immediately set capture traps for hymenoptera, which aim to capture the queens that have potentially overwintered since the previous year, thus avoiding the development of new colonies and new nests.