fig wasp

fig wasp, (family Agaonidae), any of about 900 species of tiny, solitary wasps responsible for pollinating the world’s 900 species of figs (see Ficus). Each species of fig wasp pollinates only one species of fig, and each fig species has its own wasp species to pollinate it. This extraordinary diversity of coevolution between figs and wasps has become so profound that neither organism can exist without the other.

Natural history and importance

The fig wasp’s life cycle is typified in the caprifig (Ficus carica sylvestris), a wild, inedible fig. Wasps mature from eggs deposited inside the flowering structure of the fig, called the syconium, which looks very much like a fruit. Inside the completely enclosed syconium are the tiny, individual flowers themselves. When a wasp egg is deposited in one of the female flowers, that flower develops a gall-like structure instead of a seed. The blind, wingless male wasps emerge from the galls and search out one or more galls containing a female, and upon finding one, he chews a hole in the gall and mates with her before she has even hatched. In many cases, the male then digs an escape tunnel for the female. The male then dies, having spent its entire life within the fig. The impregnated female emerges later from her gall and proceeds toward the escape tunnel or the eye of the fig (the part opposite the stem end), because she must deposit her eggs in a second fig. In departing, she passes by many male flowers and emerges covered with pollen. During her brief adult life (as short as two days), she flies into the forest to fertilize another fig and deposit another generation of fig wasps. Many female fig wasps die inside the syconium in which they laid their eggs.

The female fig wasp’s role in pollinating certain edible figs, especially Smyrna figs (F. carica), is critical to the fig grower, as most economically valuable figs require fertilization to ripen. Though she cannot lay her eggs within the edible fig (she must lay them at the base of the pistil, and the pistils of cultivated figs are longer than her ovipositor), she carries with her the pollen that fertilizes the figs and causes them to ripen. Unfertilized females perform the same role in pollination.

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This remarkable pollination system has a fundamental impact on tropical forest ecology, where Ficus species such as banyans and strangler figs are abundant. Given the short adult life span of a fig wasp, there are fig trees receiving and releasing wasps throughout the year. This results in a steady supply of Ficus fruits, providing a rich feast that attracts a host of mammals and birds and making Ficus species a critical resource for many animals during times of food shortage. If the plants were to be cut out of a forest or the fig wasps were to somehow be removed, there would almost certainly be a dramatic reduction in animal life, as is suggested by the lower population densities of fruit-eating mammals on small islands that lack Ficus species.

Major species

Although most figs are tropical, two species of fig wasps are found in North America. The female fig wasp, Blastophaga psenes, about 1.5 mm (0.06 inch) in length, was introduced into the western United States to pollinate the Smyrna fig, a commercially important variety. B. nota, originally found in the Philippines, pollinates the flowers of F. nota.