Wasps are insects that belong to the order Hymenoptera, suborder Apocrita. The term “wasp” is sometimes used in a narrower sense, to refer solely to the family Vespidae. This is because the most commonly known species of wasps, the yellow jackets (including the genera Vespula and Dolichovespula) and the hornets (genera Vespa), belong to this family.
Wasps are a successful and diverse group of insects, being traced all the way back to the Jurassic period and spanning more than 30,000 described species. Many more are thought to exist, without having yet been catalogued. One fact illustrating this enormous diversity is that each and every one of the 800+ species of fig trees (clustered mostly in the tropics) has its own species of chalcid wasp (superfamily Chalcidoidea) that helps with pollination.
Description and distribution
Wasps’ bodies are composed of 3 main parts:
- the head;
- the mesosoma, made out of the throax and the first abdominal segment;
- and the metasoma.
The head presents 2 large compound eyes, as well as several ocelli (simple eyes), which are generally arranged in a triangle on the front top of the head. Wasps also possess mandibles, which are adapted to bite and cut, but also to create suction – and, in this way, drink nectar.
The peticole, their characteristic, small waist, represents the transition from mesosoma to the metasoma. It is one of the features that distinguishes a wasp from a bee, along with the pointed lower abdomen.
Most species of wasps have 2 pairs of membranous wings, held together with small hooks; generally, the hindwings are smaller than the forewings. However, there are some species of wasps that do not have wings at all, and are thus incapable of flight. Female wasps will also have a rigid ovipositor, which, depending on the species, may or may not be retractable and which may be used to inject venom, to pierce, or to saw, be it in defence or in offense.
The largest social wasp is the Asian giant hornet (Verspa mandarinia), measuring up to 5cm in length and 76mm in wingspan; its sting measures 6mm. The largest solitary wasp is the Giant scoliid wasp (Megascolia procer), measuring up to 11,5cm in wingspan. The smallest wasps, on the other hand, are the solitary chalcid wasps from the family Mymaridae, measuring only 0,14mm. The world’s smallest insect, Dicopomorpha echmepterygis, measuring only 0,13mm, as well as the world’s smallest flying insect, Tinkerbella nana, measuring only 0,15mm, also belong to this family.
Wasps come in every colour, from the familiar yellow and brown, to metallic blue and bright red. Generally, the brighter coloured species are social species and belong to the family Vespidae; they are also the ones that have what is referred to as “warning coloration”, often consisting of black and yellow stripes. These wasps can sting, and are considered to be dangerous.
Breeding and dietary information
Wasps are able to survive in virtually all parts of the world, with the exception of the polar regions. In spite of the general picture that pops into most people’s heads when they hear the word “wasp” — that of angry, buzzing swarms of insects — the majority of wasp species are solitary; each adult female lives and, following mating, breeds independently. Most of these species are also parasitoidal, which basically means that the females will lay eggs on or in an arthropod host; the adults will not, however, feed on the host. The host will remain alive until the parasitoid larvae pupate and feed on them. Some wasps (such as those in the family Pompilidae) are specialist parasitoids of spiders, others (such as those in the family Eucharitidae) are specialist in ants, while others can even be parasitoids of parasitoids. Others, still, such as the cuckoo wasps, are kleptoparasites, laying eggs in the nests of unrelated species of wasps so that the younglings are taken care of.
This is not true for all solitary species, however. Some lay eggs directly into plant tissues, while others find or build nests in which to lay the eggs and raise the younglings. Building nests can involve digging burrows in the ground, constructing mud cells in sheltered places, or using mud to build vase-like structures, which are then attached to walls or the twigs of trees. Other species of wasps choose to nest in small groups, alongside females of the same species, each with its own cell and its own responsibilities (which are mostly about providing food) towards its own offspring. (Note that these are still considered solitary, because they do not meet the patterns of social living detailed below.)
The larvae resemble maggots in appearance. They are prepared to live in a protected environment, be this the body of a host organism or a cell in a nest; as such, they eat the provisions left by the female wasp, or are fed by it. Apart from providing them with a safe place in which to develop and with food, adults give no other maternal care.
Only around 1,000 species of wasps are social, living in colonies, much like bees. These include the yellow-jackets and hornets, and thus belong almost exclusively to the family Vespidae. This form of living is referred to as eusociality, the highest level of organization of animal sociality, and is defined by the following characteristics:
- cooperative brood care (which includes offspring from a variety of individuals);
- overlapping generations within an adult colony:
- the queen: the only one that can reproduce and whose only job is to lay eggs; it can be easily recognized, seeing as it is the largest in the group;
- the workers: females that feed the colony and take care of the offspring; they do not lay eggs;
- the drone: the male, whose only job is to mate with the queen.
- division of labour into reproductive and non-reproductive groups (the queen and the workers).
Social wasps live in nests that they construct themselves; wasps do not produce honey or wax, so they will use plant fibres (such as wood pulp) as the primary material, which is then supplemented by mud, plant secretions (such as resin), as well as secretions from the wasps themselves. Multiple brood cells are constructed, arranged in a honeycombed pattern (one or more combs), and often surrounded by a protective envelope. The placement of these nests will depend on the species: some can be found in trees, others in cavities (such as holes in the ground, tight spaces underneath homes, etc.), while others will only be found close to a source of water. A single nest can be inhabited by around 5,000-10,000 wasps at once.
The only wasps that survive the winter are the young, fertilized queens. These then emerge in the spring and build new nests, initially (late March, early April) laying around a dozen eggs. In a couple of weeks, these eggs hatch into larvae that the queen feeds until they turn into workers. Towards the end of the summer, the colony can have as many as 5,000 individuals; it will then produce males, as well as new queens. They fly away in a so-called “nuptial flight”, they mate, and the queen finds a warm place to hibernate over the winter. During this time, it will feed on its own fat. The cold weather will eventually kill the rest of the colony, the males, workers, as well as the foundation queen.
Most animals, having developed a well-founded wariness of wasps and recognizing their warning coloration, keep a reasonable distance from them. Predators of wasps include bee-eaters (the bird family Meropidae), who remove the venom from the stingers by repeatedly brushing the wasp firmly against a hard object, such as a twig; and the honey buzzard (the bird genus Pernis), who attacks the nests of social wasps and eats larvae. Also included in this category are: other species of birds, amphibians, reptiles, and some species of mammals.
Stingers are the wasps’ primary method of defence, as well as offense. Unlike bees, wasps can sting more than once, and the venom they carry contains a pheromone that causes other wasps to become more aggressive. Furthermore, when a wasp dies, it will also emit a pheromone, which will act as a warning signal to others. While social wasps will only use stingers in defence, solitary wasps can also rely on venom, in both defence and offense. The large Tarantula hawk wasp, for instance, using its venom, can easily overpower a spider many times its own size and weight.
When it comes to their dietary needs, adult wasps’ primary source of food is nectar. Young wasps, however, are carnivorous, feeding on small insects and spiders; this is main reason why some adults may be seen capturing prey.
Some wasps are predators; examples include the families Vespidae, Crabronidae, Sphecidae, and Pompilidae. They hunt a variety of creatures, most of them insects (both larvae and adults), subduing them by stinging. Most wasps will use the prey to feed the larvae, while also feeding themselves, by sucking the body fluids. There are also some species of wasps that are omnivorous. These feed on nectar, on fallen fruit, as well as carrion, such as dead insects.
When it comes to larvae, as mentioned briefly above, adults provide the food. They can do so throughout the course of the younglings’ development — a process which is referred to as progressive provisioning — or they can provide them with a source of food large enough to last them throughout development — which is referred to as mass provisioning. In many social species of wasps, larvae produce salivary secretions that are consumed by adults, seeing as they include sugars, amino acids, and essential protein-building nutrients.
Depending on the species, larvae themselves can be predatory; being deposited in clusters of eggs laid by different insects, they will then consume them as they develop. Some wasp larvae only start off as parasitoids, eating the host they had been deposited on, but convert to consuming plant tissues.
Wasps as pests
Social wasps are easily categorized as pests when they nest close to buildings, and especially if they happen to nest in buildings, in places such as attics, garages, lofts, sheds, etc. More often than not, stings are painful, but not dangerous; however, there is the possibility that people highly sensitive to the venom may suffer anaphylactic shock, which is life-threatening. If you experience symptoms such as giddiness, nausea, unusual swelling, or extreme pain following a wasp sting, you should immediately seek medical attention. This should also be done if you are stung in the mouth or neck. Most species of wasps are not aggressive, per se, but they are more easily angered that bees, and thus more likely to sting. If the nest is not close to the house, however, wasps can actually be useful in the garden, seeing as they consume dead insects and eat flies that can, themselves, be a nuisance.
When it comes to agriculture, the picture is more complicated. As detailed above, most solitary species of wasps parasitize insects — more specifically, they parasitize almost every pest insect in existence. This causes them to be extremely valued in agriculture, as biological control of pests. An example is the family Trichogrammatidae; in Brazil, farmers control sugarcane borers (Diatraea saccharalis) with the wasp Trichogramma galloi. Whiteflies — affecting tomatoes, cucumbers, aubergines, strawberries, as well as other crops and flowers, such as marigold — are controlled using Encarsia formosa, one of the first species to be used in agriculture. On the other hand, there are around 140 species of beewolves (Philanthinae) that hunt bees (including honeybees). The impact predatory wasps have on valuable insects is difficult to establish.
While most species of wasp play no role in pollination (lacking the covering of soft hairs, unlike bees), some are able and do effectively transport the pollen of several plant species. For example, wasps of the subfamily Masarinae gather and store nectar and pollen in a crop inside their bodies, pollinating flowers of Penstemon and Hydrophyllaceae. Furthermore, as mentioned briefly above, the Agaonidae wasps are the only pollinators of nearly 1,000 species of figs, thus being crucial to the trees’ survival — hence the reason why they are informally called “fig wasps”. The wasps are also dependent on the fig trees to survive, so the relationship is mutual.
It is important to correctly establish the specie of wasp you are dealing with before applying any type of eradication methods. When dealing with wasps, it is better to know ways in which you can prevent them from your property and from developing an infestation. For more details on ways in which you can ‘Prevent infestation with Wasps’, visit our relevant article, and also check out the possible methods of control through which you can get rid of wasps.