06 • 08 • 2015
The Social Wasp
Sawflies, gallflies, ruby wasps, chalcid wasps, braconid wasps, red-banded sand wasps, black-banded spider wasps, stem sawflies, European birch sawflies, conifer sawflies, carrot wasps, fairyflies, bethylid wasps… These are only some of the wasps that can be found in our forests. The second half of the summer is a time when the socially-active wasp works diligently near hives - hunting, eating, and mating.
The Vespinae subfamily of the Vespidae wasp family includes the most highly-evolved wasps and hornets. Vespidae family wasps live in hives and they build nests. The lifespan of any hive in Latvia lasts only one partial warm season.
Both meat and plants
Wasps are omnivores. Their mouth consists of a pair of upper jaws and two pairs of lower jaws, of which one is joined forming a lower lip. The upper jaws are suitable for gnawing, mauling, but the lower jaws – for licking, so they can consume food of both animal and plant origin.
Wasp larvae are fed with secretion from special glands, but when the maggots have grown, they feed only on meat products: finely-grinded animals (mostly insects). Wasps kill their prey with their strong upper jaws, seldom using their sting option.
Adult wasps also consume insects; however, for the most part their menus consist of eatables that are consumed using the lower jaw – by licking: nectar, pollen, sour fruits, tree sap, and the sweet discharge of greenflies. It is noteworthy that adult insects receive a somewhat delicious reward from maggots, which from time to time regurgitate clear food droplets full of amino acids that the wasps lick off.
Life in a hive
In the spring, after hibernation, every female that successfully endured the winter, looks for a suitable place for a new nest or hive using a paper-like substance – decayed wood, which is gnawed and moistened with saliva. A number of species build their homes in open places – on the leafage of denser trees or bushes, however, the majority – in abandoned rodent lairs, stone piles, plank or firewood stacks, under roof ridges, while some species live in even safer hideouts – attics, wood hollows, and bird-cages.
At start, the young female builds a small number of equilateral cells side by side – the first honeycomb. Afterwards, it lays unfertilized eggs in each cell. The white, worm-like larvae (also known as maggots) hatch from eggs and "hang" upside-down toward the opening of a cell.
Before reaching maturity and pupation, the first offspring are taken care of and fed by the queen alone. The pupa stage lasts three weeks until hatching of adult insects – infertile females – workers.
When the first generation of offspring turns into real insects, the queen's sole task is to lay eggs. From now on, worker wasps carry out all household duties (clean, ventilate, extend the nest, groom the queen, provide food), and also serve as soldiers – guards, which is why they have venom and a weapon – an ovipositor turned into a stinger.
The stinger is used against members from other hives but of the same species to fight for food acquisition territory and to ward off enemies. The hive's entrance is usually guarded by special sentries, however, in case of need, a number of other insects assist in fighting the opponents. An angry wasp bites its enemy with the upper jaws in order to gain support, and, bending its abdomen, it stings. A wasp can sting several times, as its weapon (unlike a bee's) has no splinters, which is why the attack can be repeated several times.
The worker wasp's lifespan is only a couple of weeks, however, thanks to the queen's diligence, the number of eggs grows and the wasp family becomes bigger. The hive's size, of course, slowly increases. The longer the summer, the bigger it becomes. At the end of summer, the size of some species' hives reaches even half a meter, and the number of its inhabitants totals several hundred.
The hive's life ends
In the fall, the queen of the social wasps stops breeding workers and begins to lay fertilized eggs. In order to make this happen, the female "resurrects" male generative cells that were "conserved" in its abdominal formation for almost a year – since the insemination the previous fall.
The fertilized eggs give life to new fertile females and males, which leave the hive to find a partner. But the family in time dissolves – the queen and worker wasps die. After the mating, all males die as well. Meanwhile, the young inseminated females find a hideout where they hibernate for the winter – until spring.
Almost any harmful insect species has at least one wasp species, which hunts it or acts as a parasite. Thus, wasps are one of the most significant insects in limiting the number of other insects. For example, parasitic wasps are often used in biological agriculture all over the world. The majority of 75,000 wasp species are parasitic – instead of building their own homes, they occupy other species' hives. A female of a parasitic species usually makes its way into the host hive, when the first worker wasps have already hatched there. The uninvited "guest" destroys the queen's eggs and replaces them with her own. The former queen is eliminated or evicted. The queen's workers are forced to take care of both the remaining locals, and the foreign maggots and eggs. Parasitic species have no worker insect groups; all offspring are capable of procreating.
