Wasps, like bees and ants, belong to the insect order Hymenoptera, characterized by a unique biological system of sex determination. Both male and female wasps exist, but the wasps encountered most often by people are almost always female. Their physical appearances, roles within the colony, and capabilities are highly specialized based on their sex.
How Wasps Determine Sex
The biological mechanism governing sex in wasps is known as haplodiploidy, a system that determines an individual’s sex based on the number of chromosome sets it possesses. This genetic structure is distinct from the X-Y chromosome system found in humans and other mammals. In haplodiploidy, the number of chromosome sets dictates whether an egg develops into a male or a female wasp.
Female wasps are diploid, meaning they develop from fertilized eggs and possess two sets of chromosomes, one from the mother and one from the father. Conversely, male wasps are haploid, meaning they develop from unfertilized eggs and only possess one set of chromosomes, inherited solely from the mother. This means a male wasp has a mother but no father.
This system grants the queen wasp control over the sex of her offspring. The queen stores sperm from her mating flight in a specialized internal organ called the spermatheca. When laying an egg, the queen can choose to either fertilize it with stored sperm, resulting in a female, or allow it to pass unfertilized, which produces a male. The vast majority of the eggs laid during the colony’s growth phase are fertilized, ensuring a large workforce of female wasps.
The Distinct Roles of Male and Female Wasps
The different genetic compositions of male and female wasps lead to distinct roles and behaviors within a social colony. Female wasps assume all functional roles necessary for colony survival and growth, including three main types: the queen, workers, and gynes.
The queen is the single reproductive female who founds the colony and lays all the eggs. Worker wasps are sterile females that perform all physical labor, such as foraging for food, caring for the young, building the nest from chewed wood fiber, and defending the colony.
The stinger is a modified ovipositor, or egg-laying organ, meaning that only female wasps possess the ability to sting. This defensive weapon is present in both the queen and the workers. Since the workers are the ones actively foraging and defending the nest, they are the ones most likely to be encountered by people. The third type of female, the gynes, are new reproductive females produced late in the season who will go on to become the next season’s queens.
In contrast, male wasps, often referred to as drones, have one sole purpose: reproduction. They do not participate in any of the colony’s essential tasks, such as foraging, nest construction, or larval care. Because the male wasp does not have an ovipositor, it lacks a stinger, making it completely incapable of stinging.
Sexes and the Social Wasp Life Cycle
The presence and ratio of male and female wasps change over the course of the season, coinciding with the colony’s life cycle. A wasp colony begins in the spring when a single fertilized gyne, having survived the winter in hibernation, emerges to build a small nest and lay the first eggs. These initial eggs are all fertilized and develop into the first generation of sterile female workers.
Throughout the summer, the colony focuses on growth, with the queen continuously laying fertilized eggs to maximize the worker population. The workers take over all duties, allowing the queen to focus solely on egg production. The production of males and new gynes is strategically timed for the late summer or early autumn.
At this point, the queen begins to lay unfertilized eggs, which develop into the haploid male drones. She also lays fertilized eggs in specially enlarged cells, which are fed a richer diet to develop into the new reproductive females, the gynes. The males and gynes leave the nest to mate with individuals from other colonies, ensuring genetic diversity. After mating, the male wasps die, having fulfilled their purpose. The old queen and all the sterile workers also die as the weather cools, and only the newly mated gynes survive to find a sheltered place to hibernate until the following spring.