Eusocial behavior among wasps is found only in certain members of the family Vespidae. These insects are commonly called paper wasps, hornets, and yellowjackets. They build communal nests by mixing wood fibers with saliva to form a paper-like material that can be molded into brood cells and other nest components. The brood comb (cells where larvae are reared) is always constructed like an inverted umbrella with open ends of the hexagonal cells facing downward. Workers usually cling to the underside of the comb as they guard the nest, feed the larvae, and perform other housekeeping chores. All social wasps are carnivores; their prey consists mostly of caterpillars and flies. The wasps chew up their victims' bodies into a paste that can be fed to their larvae and, in return, the larvae produce a nutritional syrup that is consumed by the adults. A small colony of 200 yellowjackets may kill and eat about 5000 caterpillars over the course of a summer.
The caste structure of the wasp's social system appears to be maintained primarily through aggressive interactions among the colony members. If a queen fails to sustain her dominant role, she will be replaced by another fertile female who assumes primary responsibility for egg production. Males develop only from unfertilized eggs (usually laid by unmated workers).
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|Queen - Fertile adult female and foundress of the colony.|
Drone - Fertile adult male - develops from an unfertilized egg.
|Unmated adult females - generally the daughters of the queen.|
In tropical climates, social wasps are active throughout the year. New colonies often form by fission (swarming) in which a fertile queen and a group of workers leave a large parent nest and set up housekeeping for themselves. In temperate climates, wasp colonies are founded in early spring by one or more queens who mated the previous summer and hibernated throughout the winter. The foundress constructs a small nest containing just a few brood cells. After laying a small complement of eggs, she feeds and cares for her offspring until they emerge as adults. These individuals (all females) become her workers. They assume all brood care, foraging, and housekeeping duties.
The queen continues to lay eggs and the colony grows larger throughout the summer.
In early fall, the colony structure begins to break down. Unfertilized eggs give rise to males who mate with newly emerging females that will overwinter and found new colonies the following year.
- Types of social wasps. There are about 20 species of social wasps in North America and more than 700 species world-wide. They can be divided into three groups:
- Yellowjackets. Nests are usually built in underground cavities, such as old rodent burrows.
- Hornets. Nests are always located above ground. Some species colonize hollow trees while others hang brood comb from a tree branch and surround it with paper walls for protection against the weather and natural enemies.
- Common paper wasps. Nests are typically found under sheltered overhangs where they are protected from wind and rain.