Page:Popular Science Monthly Volume 41.djvu/187

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175
THE YUCCA MOTH AND YUCCA POLLINATION.

large load of pollen for the purpose of pollination. Another organ which is characteristic is the ovipositor (Fig. 4, b, d), which PSM V41 D187 Genital characters of pronuba yuccasella.jpgFig. 4.—Genital Characters of Pronuba yuccasella: a, tip of ♀ abdomen rendered somewhat transparent; b, basal joint of ovipositor; c, its sculpture; d, terminal joint of same; e, tip still more enlarged; f, genitalia ♂ from side; g, genitalia ♂ from above; h, undeveloped egg from ovary—enlarged. is delicate and extensile, being a combination of lance and saw, and admirably adapted for cleaving through the young fruit and then running the egg, which is long and filiform, into the ovarian cavity.

Though all the acts of the female are nocturnal, it is not at all difficult to follow them with a lantern, for, albeit ordinarily shy, she may be closely approached when she is about to oviposit. Her activity begins soon after dark, but consists at first in assiduously collecting a load of pollen. She may be seen running up to the top of one of the stamens, and bending her head down over the anther, stretching the maxillary tentacles, so wonderfully modified for the purpose, to their fullest extent, the tongue uncoiled and reaching to the opposite side of the stamen (Fig. 6). In this manner she is able to obtain a firm hold of the same while the head is kept close to the anthers and moved peculiarly PSM V41 D187 Pronuba yuccasella.jpgFig. 5.—Pronuba yuccasella: l, male; m, female chrysalis—hair-line showing natural size. back and forth, something as in the motion of the head of a caterpillar when feeding. The maxillary palpi are used in this act very much as the ordinary mandibles are used in other insects, removing or scraping the pollen from the anthers toward the tentacles. After thus gathering the pollen, she raises her head and commences to shape it into a little mass or pellet by using her front legs very much as a cat does when cleansing her mouth, sometimes using only one leg, at another time both, smoothing and pressing the gathered pollen, the tentacles meanwhile stretching and curving. After collecting all the pollen from one anther, she proceeds to another and repeats the operation, then to a third and fourth, after which, with her relatively large load—often thrice as large as the head—held firmly against the neck and front trochanters, she usually runs about or flies to another plant: for I have often noticed that ovi-