By Rabbi Moshe Bloom
Torah VeHa’aretz Institute

In the Minchah haftarah of Yom Kippur, we read from the book of Yonah on his prophecy of the destruction of Ninveh. After the people of Ninveh repent and the prophecy is not fulfilled, Yonah, anguished, goes to the outskirts of the city: “And the L-rd, G-d, provided a kikayon plant, which grew up over Yonah, to provide shade for his head and save him from discomfort; Yonah was very happy about the plant. But the next day at dawn, G-d provided a worm, which attacked the plant so that it withered” (Yonah 4:6–7).

The kikayon became a symbol of transience and a G-dly lesson on compassion: “The L-rd said: ‘You cared about the plant, which you did not work for and which you did not grow, which appeared overnight and perished overnight. And I should not care about Ninveh, that great city…?” (ibid., 10–11).

The Talmud (Shabbat 21a) identifies the kikayon as Ricinus communis, known as the castor-oil plant, which is common in the Ninveh area (modern-day Iraq): “What is kik oil? … Reish Lakish said: the castor plant [kikayon] of Jonah. Rabba bar bar Chana said: I have seen the species of the castor plant of Jonah, and it is similar to the ricinus tree and it grows in swamps, and they place it at the entrance of shops [for shade,] and they produce oil from its seeds, and all the sick people of the West [Land of Israel] rest [beneath it].”

The plant is called kiki in Greek, while the Mishnah refers to it as kik. This oil is mentioned in the Mishnah (Shabbat 2:1) under the list of forbidden oils for lighting Shabbat candles: “And they may not kindle with … kik (castor) oil.” Herodotus (The Histories II, 94) describes the kikayon: “The Egyptians, who live around the marshes, use an oil drawn from the castor-berry, which they call kiki. They sow this plant, which grows wild in Hellas (Greece), on the banks of the rivers and lakes; sown in Egypt, it produces abundant fruit, though malodorous; when they gather this, some bruise and press it, others boil after roasting it, and collect the liquid that comes from it. This is thick and useful as oil for lamps, like olive oil, and gives off a disagreeable smell.”

The Talmud explains that the reason why the various oils are disqualified in the Mishnah (including castor oil) is that “it does not draw up effectively from the wick.” The Rishonim explain that castor oil is thick and is not drawn up easily by the wick, so it does not illuminate well. This creates a concern that someone would tilt the lamp to increase its light, thus transgressing the biblical prohibition of kindling fire on Shabbos. Its pungent odor may be another reason that Chazal prohibit its use for lighting Shabbat candles.

Dioscorides, a Greek doctor, pharmacologist, and botanist, describes the plant and mentions that its oil was produced for its medicinal qualities: “The castor-oil plant resembles the fig tree but is smaller … its oil is used for external and internal medicine” (De Materia Medica).

The castor-oil plant grows wild in Israel, originating from tropical Africa. In Israel, it can be found in the Jordan Valley, the Coastal Plains, and river beds all over the country. Its seeds are used to produce oil for medicinal purposes and as a motor lubricant for planes.

The Toxic Kikayon

Castor-oil plant seeds are highly poisonous, but they are encased by a hard shell. If swallowed whole, they exit the system without causing damage; if cracked or chewed, however, even one seed contains sufficient toxins that can be lethal to a child. The plant’s leaves are also toxic, serving as a feeding deterrent, so very few insects infest its leaves.

In Israel, there are several aphids that infest its leaves, but until recently no caterpillars (Lepidoptera) had been found that feed on them.

How is it possible that the kikayon withered overnight?

In 2002, Dr. Gunter Müller discovered caterpillars from the Arctiidae family that feed on the castor-oil plant in streams in the Dan area — a species of the tiger moth. Müller was the one to discover the species, and named it Olepa schleni. He raised the caterpillar in his lab and found that it feeds on the castor-oil plant exclusively—it eats the leaves and branches, and can even handle its poisonous seeds. It has yet to be tested what the caterpillar does with the toxins. Müller studied the caterpillar’s behavior and found that it indeed can be guilty of devouring Yonah’s kikayon overnight. Note that in the Tanach, caterpillars are often referred to as worms.

The female butterfly lays her eggs on the underside of the leaves. At this point, they are concentrated in groups that are attached to the leaves by strands of silk. At the third stage of the caterpillars’ development, they can eat the plant’s leaves, arteries, and stems. In the slough stage (fourth–sixth), the caterpillars can be found on the leaves only in the night hours (as described in the book of Yonah), when they feast on every part of the plant. At sunrise, they hide under the remains of the leaves that fell to the ground, while in groups of up to 50 caterpillars. It is at this stage, if there is a sufficient amount of caterpillars, that they are capable of devouring the entire plant overnight.

These caterpillars are extremely rare in Israel today and we do not know if they are found in Iraq today. Undoubtedly, though, the redactor of the book of Yonah was certainly familiar with these “worms.”

In conclusion, it is interesting to note that it is precisely this highly toxic plant that provides Yonah — who prophesized the death of a nation — with shade. And then, many small caterpillars together have the ability to destroy this toxic plant overnight (in nature, at least; it seems that just one sufficed in the book of Yonah), just as the repentance of all of the people of Ninveh was able to undo the lethal prophecy looming over their heads.

May we all merit that our collective teshuvah, as well, will have the power to disintegrate any lethal “kikayon” in our national and personal lives. n

Rabbi Moshe Bloom is head of the English department of Torah VeHa’aretz Institute. Torah VeHa’aretz Institute (the Institute for Torah and the Land of Israel) engages in research, public education, and the application of contemporary halachic issues that come to the fore in the bond between Torah and the Land of Israel today. For additional information and inquiries, email or call 972-8-684-7325.

“Jonah the Prophet, The Kikayon, and The Caterpillar.” Translated and adapted by Rabbi Moshe Bloom, Torah VeHa’aretz Institute, from Meir Cohen, Zeman Makom, and Prof. Rachel Galon.


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