Fig. 53.—The caterpillar of the moth, Carpocapsa saltitans, removed from the jumping bean: magnified three diameters. Observe the jaws (with which the circular plate is cut in the bean before the grub becomes a chrysalis), eyes, three pairs of pointed legs, four sucker legs placed in the middle region, and followed by three segments without legs, and a terminal segment with a pair of suckers. (Drawn from nature for this work.)
[Transcriber’s Note: The original image is approximately 1½ inches (3.5cm) high and ½ inch (1.5cm) wide.]
So far so good. The next questions are: What Mexican plant is it that forms the capsule or tripartite fruit in which the caterpillar is found? How did the caterpillar get there? What kind of an insect does it turn into, and when? I will answer the last question first. The caterpillar turns into a chrysalis in the early part of the year, having first cut a perfectly circular ring in the shell of the capsule. The circular plate thus within the ring is not disturbed, and cannot be observed without very close inspection. The making of this perfectly circular cut without removing the piece marked out must be effected by a rotation of the caterpillar’s head and jaws as a centre-bit—an astonishing performance. But when the moth emerges from the chrysalis, a gentle push is enough to cause the little circular plate to fall out, and the moth creeps through the hole to the outer world. The moth, which comes out of the chrysalis-coat, is a very pretty little creature (see [Fig. 54]), measuring two-thirds of an inch across the opened wings, which are marked with dark and reddish-brown-coloured bands. It is a close ally of the British codling moth, the caterpillar of which eats its way into the core of apples, and is familiar to all growers and eaters of that fruit. The codling moth and the Mexican “jumper” belong to a group of small moths called Tortricinæ, and they are named respectively Carpocapsa saltitans (the one whose grub or caterpillar inhabits the “jumping bean”) and Carpocapsa pomonana, the codling moth. There are other British species of Carpocapsa, the grubs of which eat into the acorn, the walnut, the chestnut, and the beechnut—a distinct kind or species for each. None of these grubs cause the nuts they attack to “jump.”
Fig. 54.—The moth, Carpocapsa saltitans, which escapes from the jumping bean or segment of the fruit of the Mexican spurge, Sebastiana palmeri, in which its caterpillar and chrysalis have passed their lives. The crossed lines indicate the natural size of the moth. (Drawn from nature for this work.)
[Transcriber’s Note: The crossed lines are approximately ¼ inch (0.75cm) high and ¾ inches (2cm) wide in the original.]
The “jumping bean” of Mexico is a segment of the triply divided fruit of a large spurge, which is called Sebastiana palmeri. The spurges are known in England as little green-leaved annuals, with yellow-green flowers and a milky juice. Botanists call them the Euphorbiaceæ, and in that “natural order” are included the boxwood tree and some tropical trees of great value and importance. None other than the Brazilian indiarubber tree, Hevea, of which we hear so much nowadays, its rubber to the value of £14,000,000 being exported every year from Brazil, is one of them. So also is the Chinese candle-tree, which furnishes a tallow-like fat, made into candles in China. Others are the croton oil and the castor oil shrubs, natives of India, and the manihot or tapioca plant. The fruits of Sebastiana (the jumping bean) are very much like those of the croton; and as there are crotons (though not the one of the purgative oil) in abundance in Mexico, it has taken some time to make sure that the “jumping bean” is not the fruit of a croton, but that of the allied plant Sebastiana. It appears that there is no commercial value for this plant, and that those capsules which happen to contain a grub and move are collected from the ground by the native Mexican boys and sold as curiosities.