What are the characteristics of the living habits of paper wasps?
Paper wasps are a group of insects with social behavior. Species in the family Eumenidae have no nest in normal times and live freely. When laying eggs, the female wasp builds a mud cell or chooses a suitable bamboo tube, lays eggs inside, and at the same time stores the larvae of other insects or spiders that have been captured and paralyzed by stinging. One cell holds one egg, and each is sealed separately. The larvae hatched from the eggs feed on the stored prey. After pupating and emerging as adult wasps, they bite through the nest opening and fly out.
Other species of paper wasps, the hornets, live in nests throughout their lives. In the colony there are differences among the queen wasp, worker wasps (also called worker bees) (female), and male wasps. The queen wasp is a female wasp that mated and was fertilized with a male wasp after autumn of the previous year. They store sperm in the spermatheca and use it in batches during that year. Male wasps die soon after mating. When the weather gradually turns cold, fertilized female wasps leave the nest one after another to seek wind-sheltered places such as wall cracks and haystacks, huddling together to overwinter. In the spring of the following year, the surviving female wasps disperse from the cluster and move about separately, each seeking a suitable place to build a nest and lay eggs. The fertilized eggs they lay develop into female wasps, and unfertilized eggs develop into male wasps. As worker wasps increase, the nest gradually expands. Worker wasps are responsible for building the nest and rearing larvae. In central China there are 3 peak outbreaks each year. After autumn, male wasps in the nest account for about 1/3 of the total, which is the period with the most male wasps in the year.
Paper wasps generally emerge from dormancy and become active when the temperature is 12-13°C, begin building nests at 16-18°C, and overwinter when the temperature drops to 6-10°C after autumn. In spring they are most active at noon when the temperature is high. At noon in summer, when it is hot, they often pause activity. At night they return to the nest and remain still.
Paper wasps have a phototactic habit. They stop activity when the wind force is above level 3. They are most suited to activity when the relative humidity is 60-70%. On rainy days they stop going out. Paper wasps are fond of eating sweet substances. Within a range of 500 m, hornets can clearly identify direction and return to the nest smoothly. Beyond 500 m, they often lose their way and forget to return.
The nests built by hornets of the subfamily Polistinae and the subfamily Vespinae are made of paper, not beeswax. In this respect, they differ from honeybees and other hornets.
Paper wasps are animals with complete metamorphosis. Their life goes through four stages: egg, larva, pupa, and adult. The body appearance differs at each stage. The egg is often oval, white, smooth, with 1 in each nest cell. Its base is fixed by a silk stalk until the larva hatches, so even if the nest is hanging upside down it will not fall. Worker wasps are responsible for feeding. When development is mature, the body gradually changes from crystal clear to bright yellow. Then a thin cocoon is sealed over the cell opening and it transforms into a pupa. After emerging as an adult, it breaks out of the cocoon. From egg to emergence takes only two to three weeks.
In the larval stage, paper wasps feed on other small insects, especially caterpillars. Larvae of Eumenidae species, inside the sealed nest built by the parental adult wasps, feed on other insects stored by the parents that have been paralyzed. Larvae of other hornets are fed in the nest by adult wasps with chewed-up other insects. After feeding, the larvae often secrete a liquid that adult wasps like to eat. At the end of the midgut in the larval digestive tract, the peritrophic membrane forms a closed sac that does not connect with the excretory opening. Excrement is stored in this sac and remains free in the body. After pupation, this sac dries, hardens, and turns black, and is shed together with the molt.