Friday, April 22, 2005



There is an interesting post on wasps, termites, and turkeys at Pratie Place, which mentions the contribution of wasps to modern paper-making. Wasps are also vital to the cultivation of figs.

Webster's Dictionary (1913) defines caprification as "The practice of hanging, upon the cultivated fig tree, branches of the wild fig infested with minute hymenopterous insects." The word comes from caper (goat) and ficus (fig). It is said that only goats eat caprifigs (wild figs), whence the name. Members of the order Hymenoptera include fig wasps.

Scientists were slow to recognize the value of caprification. Gilbert Waldbauer, in What Good Are Bugs? Insects in the Web of Life (Cambridge: Harvard University Press, 2003), p. 37, writes:
For centuries fig growers in the Old World knew that Smyrna figs need to be pollinated. They grew caprifigs, and when the female "fig" trees were ready for pollination, they hung in each tree a basket containing a few caprifigs, which produced enough wasps to pollinate the female inflorescences. But many botanists thought that this practice of "caprification" was useless, no more than a superstition of ignorant peasants. Condit reported that as late as 1898 a botanist "was ridiculed by scientists in Italy for his belief in the necessity for caprification." In 1887, Dr. Gustave Bisen was hooted down in Fresno, California, when he recommended the importation of caprifigs and fig wasps. But reason eventually prevailed, and by the beginning of the twentieth century caprifigs and the fig wasp had been introduced into California, and ever since large commercial crops of various varieties of the Smyrna fig have been grown there.
"Condit" is a reference to I.J. Condit, The Fig (Waltham: Chronica Botanica, 1947).

Pliny the Elder, in his Natural History, discusses caprification in two passages. Neither he nor any other ancient writer understood pollination, first discovered in 1787 by Conrad Sprengel (Waldbauer, pp. 12-13). Pliny erroneously assumes that the wasps are produced by spontaneous generation, and makes various other mistakes.

Pliny, Natural History 15.21 (tr. John Bostock and H.T. Riley):
The fig, the only one among all the pomes, hastens to maturity by the aid of a remarkable provision of Nature. The wild-fig, known by the name of "caprificus," never ripens itself, though it is able to impart to the others the principle of which it is thus destitute; for we occasionally find Nature making a transfer of what are primary causes, and being generated from decay.

To effect this purpose the wild fig-tree produces a kind of gnat. These insects, deprived of all sustenance from their parent tree, at the moment that it is hastening to rottenness and decay, wing their flight to others of kindred though cultivated kind. There feeding with avidity upon the fig, they penetrate it in numerous places, and by thus making their way to the inside, open the pores of the fruit. The moment they effect their entrance, the heat of the sun finds admission too, and through the inlets thus made the fecundating air is introduced. These insects speedily consume the milky juice that constitutes the chief support of the fruit in its infant state, a result which would otherwise be spontaneously effected by absorption: and hence it is that in the plantations of figs a wild fig is usually allowed to grow, being placed to the windward of the other trees in order that the breezes may bear from it upon them. Improving upon this discovery, branches of the wild fig are sometimes brought from a distance, and bundles tied together are placed upon the cultivated tree.

This method, however, is not necessary when the trees are growing on a thin soil, or on a site exposed to the north-east wind; for in these cases the figs will dry spontaneously, and the clefts which are made in the fruit effect the same ripening process which in other instances is brought about by the agency of these insects. Nor is it requisite to adopt this plan on spots which are liable to dust, such, for instance, as is generally the case with fig-trees planted by the side of much-frequented roads: the dust having the property of drying up the juices of the fig, and so absorbing the milky humours. There is this superiority, however, in an advantageous site over the methods of ripening by the agency of dust or by caprification, that the fruit is not so apt to fall; for the secretion of the juices being thus prevented, the fig is not so heavy as it would otherwise be, and the branches are less brittle.
Pliny, Natural History 17.43-44 (tr. John Bostock and H.T. Riley):
As to caprification, the effect of that is to ripen the fruit. It is beyond all doubt that in caprification the green fruit gives birth to a kind of gnat; for when they have taken flight, there are no seeds to be found within the fruit: from this it would appear that the seeds have been transformed into these gnats. Indeed, these insects are so eager to take their flight, that they mostly leave behind them either a leg or a part of a wing on their departure. There is another species of gnat, too, that grows in the fig, which in its indolence and malignity strongly resembles the drone of the beehive, and shows itself a deadly enemy to the one that is of real utility; it is called centrina, and in killing the others it meets its own death.

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