Enjoyment seems to be the only motive the fly has for riding on the back of the African beetle shown in the upper part of this illustration. Beneath is shown the well named honey-pot ant with its distended body full of honey, which it gives away to any hungry working ant.
A diet of mushrooms, or fungus, is not the only thing for which these little blind, light-shunning cockroaches are indebted to their landlords, the ants, for often one of them may be seen to mount upon one of the latter, and take a ride on its back. They seem especially fond of the soldiers, as horses, and will sit perched on their enormous heads, as they walk up and down in a stately sort of way, sometimes for quite a long time. Enjoyment seems here to be the only motive, and perhaps it is a natural one, since there is a fly in Africa which seems to have quite a passion for riding on the back of a beetle. “Across the mouth of the Seyhouse,” says the Rev. Mr. Eaton, “on sandy pasture-land bordering the seashore, big coprophagous beetles—it sounds abusive, but no harm is meant—are common, sheltering in large holes in the soil, when at rest, and running about on business. A small species of Borborinæ (that is the fly) may often be seen riding on their backs, chiefly on the pronotum and about the bases of the elytra, sometimes half a dozen females on one beetle. The beetles occasionally throw themselves on their backs, and try to get rid of them by rolling; but the flies elude all their efforts to dislodge them, dodging out of harm’s way into the jointures of the thorax, and darting from back to breast, and back again, in a way that drives the beetle nearly mad. In vain she scrapes over them with her legs, in vain does she roll over, or delve down amongst the roots of the herbage: the flies are as active as monkeys (not perhaps a very striking simile here), and there is no shaking them off. It is difficult (such is their strange predilection) to get them off into the killing-bottle. Nothing (not even the killing-bottle) persuades them to fly, and they would very much rather stick to the beetle than——” what? Not go to heaven, but “be driven off it down the tube.”[[16]] The tube must be the neck of that same bottle. This, surely, is a case of infatuation if ever there was one. Eccentric fly! And what must be the charms of a beetle that can prevail over those of cyanide of potassium! But the beetle, it must be remembered, is a coprophagous one. There may be a world of explanation in a word like that.
CHAPTER V
From biped to quadruped—Flies that borrow wings—Sit-o’-my-head—A novel cradle—Flies that kill bees—Nature’s sadness—Consolations of the future—The Tachina fly and the locust.
ALTHOUGH from the way in which the story is told, one might imagine that the fly here was merely enjoying a ride upon beetle-back, yet, from the efforts made by the latter to shake off its persecutors, and, still more, because these were of the female sex, the probability is that we have here to do with a case of parasitism. The fly, we may almost feel certain, was endeavouring to lay its eggs, and the reason why she took so long about it was that she required a certain spot upon the beetle in order to do so, and that the beetle’s efforts, though appearing futile, were more or less successful in guarding this spot. At any rate, if this was not the case here, it is so in many other instances, various flies being parasitic on various other insects. Not all of these are fatal to the object of their choice, which, if it affords them board as well as lodgings, may only do so to the extent of its blood. Such are the curious family of Hippoboscidæ, or Bird Ticks, who begin life with wings, but are so little appreciative of the powers which these confer that, having found the creature upon whom they elect to live, they bite them off, or otherwise wilfully rid themselves of them, after the manner of ants and termites, thus offering yet another example in the insect world of
“one whose hand,
Like the poor Indian, flung a pearl away
Richer than all his tribe.”