The relationship between the fig tree and the fig wasp is a specialized mutualism in the plant kingdom. This intricate partnership ensures the reproduction of over 750 species of fig trees (Ficus genus) and the survival of their obligate pollinators, the fig wasps. The fig tree depends entirely on its specific wasp species for pollination, and the wasp cannot complete its life cycle anywhere else. This biological contract is built around a unique flowering structure that creates a closed environment for this essential exchange.
The Unique Anatomy of the Fig
What most people call a fig fruit is actually a hollow, fleshy structure known botanically as a syconium, which is an inverted cluster of hundreds of tiny flowers. The fig is not a true fruit, but a swollen receptacle that encloses the flowers on its inner surface. This unusual anatomy hides the flowers from typical pollinators, requiring a specialized mechanism for pollen transfer.
The syconium is a sealed chamber with a small external opening called the ostiole, located opposite the stem. This aperture is guarded by overlapping bracts, creating a tight passage that serves as the exclusive entry point for the fig wasp. Inside, the fig houses three types of flowers: male, short-styled female, and long-styled female flowers. The length of the styles dictates the fate of both the wasp and the fig’s seeds.
Male flowers, which produce pollen, are located near the ostiole, ripening later to coat the exiting wasps. Female flowers are separated based on the length of their styles, the tube connecting the stigma to the ovary. Short-styled flowers are accessible to the wasp’s ovipositor for egg-laying, developing into galls that nourish the larvae. Long-styled flowers have ovaries safely out of reach, ensuring they develop into seeds. This separation allows the fig to simultaneously produce the next generation of wasps and its own seeds.
The Fig Wasp’s Role in Pollination
The process begins when a female fig wasp, carrying pollen from her birth fig, finds a receptive syconium by following its chemical scent. She seeks a new fig in which to lay her eggs. She forces her way through the narrow ostiole, often shearing off her wings and parts of her antennae. This sacrifice renders her flightless and unable to exit the fig, making her entry a one-way trip.
Once inside, the female wasp moves through the chamber, attempting to lay eggs in the ovaries of the female flowers. She uses her ovipositor to deposit eggs into the short-styled flowers, which develop into galls that nourish the larvae. As she crawls, the pollen she carried brushes off her body onto the receptive stigmas of the long-styled flowers. These long-styled flowers, protected from egg-laying, are fertilized to produce viable seeds.
The wasp ensures the fig’s reproductive success by fertilizing the long-styled flowers, while the fig ensures the wasp’s success by allowing her to lay eggs in the short-styled flowers. Having completed her work, the female wasp dies inside the syconium shortly after. The fig then begins ripening, chemically digesting the wasp’s body with the enzyme ficin, absorbing its nutrients as the seeds and larvae develop.
The Wasp Life Cycle Inside the Fig
Following pollination, the fig focuses on maturation, including the development of the wasp larvae inside the galls. After several weeks, the first wasps to emerge are the males, which are wingless, often blind, and distinct from the females.
Their first action is to chew holes into the galls of their unhatched sisters and mate with the females while they are still inside. These fertilized females will carry the genetic material for the next generation. After mating, the males cooperate to chew an exit tunnel through the thick wall of the syconium, creating a passage for the females to escape.
The male wasps die within the fig, having expended their energy on mating and creating the exit. The newly matured female wasps emerge from their galls and navigate toward this tunnel. As they move out, they pass by the male flowers, which have ripened and burst open to release their pollen. The females actively collect this pollen, storing it in specialized pockets on their bodies, before flying out to search for a new fig and begin the cycle anew.
Edible Figs vs. Wild Figs
The complex pollination mechanism distinguishes figs that rely on the wasp from those that do not. Wild figs, known as Caprifigs, are male trees that serve as the nursery for the fig wasp life cycle. Caprifigs contain the pollen and short-styled flowers necessary for wasp reproduction, but they are generally inedible to humans.
Edible figs fall into two main categories: those requiring pollination and those that do not. Smyrna-type figs, such as the Calimyrna, require the fig wasp for successful pollination and fruit maturation. If unpollinated, the immature fruits will drop. These figs rely on nearby Caprifigs to supply the wasp with the pollen needed to fertilize their long-styled female flowers.
The most common figs sold commercially, like ‘Brown Turkey’ or ‘Black Mission’ varieties, are known as Common figs. These cultivars have female flowers that do not require pollination to set fruit, a process called parthenocarpy. They ripen without the wasp’s intervention, meaning they do not contain wasp remnants. This trait allows them to be grown in areas without the fig wasp and simplifies cultivation.