twenty-five blossoms I have counted five flies thus held in captivity—three dead and two dying—and the same bunch had captured a long-legged, lace-winged caperer, whose struggles to free himself were as desperate as futile. On any large bunch of these flowers one can see mementoes of past tribulations. Here and there a blossom still holds a little black leg, the price of the liberty of some insect who has gone off free, but a cripple.
A flower so highly organized as the milkweed seldom receives and nourishes all comers. In one peculiarity of structure the milkweeds are like the orchids, that royal family of plants, for the orchids also send their pollen abroad massed into two clusters, which are united by a disk. But each orchid has its own very select and small circle of guests, and some among them endeavor to please one butterfly or moth friend, him and him alone. They are, in evolutionary language, "highly specialized."
On the other hand, a flower which keeps open house to all comers is generally primitive in color and structure. Such blossoms are apt to be yellow or white, with flat, open corollas, and without spurs, honey jars, or covering to protect the pollen. So the milkweed is something of a problem to the evolutionary botanist. Can he, for example, explain the fate of those hapless flies which, like Haman of old, come to a feast, but get only imprisonment and death? These unfortunates are but a small proportion of the milkweed's fly visitors. The great majority make off, after taking their fill of nectar, without carrying off any portion of the pollen which the flower is endeavoring to send to its neighbors. This waste of nectar is bad for the milkweed, which would be better off with fewer fly visitors. So the flower would profit by any device which would discourage these many flies, without deterring those useful and desired visitors, the bees. Will flies learn after a while to shun the milkweed's dangerous sweets, so that they may all be left for worthier and more welcome guests? And how many generations will it take this proverbially foolish insect to lay the lesson to heart?